From 1ddadde63c60fb99f666e115b4bd52dc3b68456a Mon Sep 17 00:00:00 2001
From: Tobias Werth <werth@cs.fau.de>
Date: Sat, 29 Nov 2025 18:03:47 +0100
Subject: [PATCH 1/5] Make sure the g++ version is modern enough where it is
 available but not the default (such as old Ubuntu LTS).

---
 .github/jobs/configure-checks/setup_configure_image.sh | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/.github/jobs/configure-checks/setup_configure_image.sh b/.github/jobs/configure-checks/setup_configure_image.sh
index b3bdcad686..7d492454ec 100755
--- a/.github/jobs/configure-checks/setup_configure_image.sh
+++ b/.github/jobs/configure-checks/setup_configure_image.sh
@@ -10,6 +10,8 @@ case $distro_id in
         dnf install pkg-config make bats autoconf automake util-linux -y ;;
     *)
         apt-get update; apt-get full-upgrade -y
+        # Install g++-12 to make sure we can use -std=c++20
+        version=$(g++ -dumpversion 2>/dev/null | awk -F'.' '{print $1}' 2>/dev/null || echo 0); [ "${version}" -lt 12 ] && apt install -y g++-12
         apt-get install pkg-config make bats autoconf -y ;;
 esac
 

From 9ceed94cc540d430aac84d1920700f253e81d8c0 Mon Sep 17 00:00:00 2001
From: Kevin Jilissen <info@kevinjilissen.nl>
Date: Sat, 29 Nov 2025 17:28:45 +0100
Subject: [PATCH 2/5] Disable diff selection if there is no other

Also, do not store the preferred diff tag when there is no other diff.
This prevents going back to no-diff after viewing a submission without a
diff.
---
 webapp/public/js/domjudge.js                             | 2 +-
 webapp/templates/jury/partials/submission_diff.html.twig | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/webapp/public/js/domjudge.js b/webapp/public/js/domjudge.js
index 0cb848ba23..68d8a7373b 100644
--- a/webapp/public/js/domjudge.js
+++ b/webapp/public/js/domjudge.js
@@ -1422,7 +1422,7 @@ function initDiffEditor(editorId) {
         });
 
         const selected = select[0].options[select[0].selectedIndex];
-        if (selected && selected.dataset.tag) {
+        if (!select[0].disabled && selected && selected.dataset.tag) {
             setDiffTag(selected.dataset.tag);
         }
 
diff --git a/webapp/templates/jury/partials/submission_diff.html.twig b/webapp/templates/jury/partials/submission_diff.html.twig
index fae494ecae..de391147c4 100644
--- a/webapp/templates/jury/partials/submission_diff.html.twig
+++ b/webapp/templates/jury/partials/submission_diff.html.twig
@@ -26,7 +26,7 @@
             {% endif %}
             <div class="btn-group">
                 <a href="#" role="button" class="btn btn-secondary btn-sm pe-none" aria-disabled="true"><i class="fas fa-code-branch"></i></a>
-                <select class="diff-select btn btn-secondary btn-sm form-select-sm text-start" aria-label="Submission to diff against">
+                <select class="diff-select btn btn-secondary btn-sm form-select-sm text-start" aria-label="Submission to diff against" {%- if otherSubmissions is empty %}disabled="true" aria-disabled="true"{%- endif %}>
                     <option value="" data-tag="no-diff">No diff</option>
                     {%- for other in otherSubmissions %}
                         <option value="{{ other.submitid }}" data-url="{{ path('jury_submission', {submitId: other.submitid}) }}" {%- if other.tag %} data-tag="{{ other.tag }}" {%- endif %}>

From ec6da347dc854cd10d98bfd1cdab5f4134277f8d Mon Sep 17 00:00:00 2001
From: Tobias Werth <werth@cs.fau.de>
Date: Sun, 23 Nov 2025 15:31:05 +0100
Subject: [PATCH 3/5] C++-ify lib.error.c

---
 judge/evict.cc                    |   2 -
 judge/runguard.cc                 |  12 +--
 lib/Makefile                      |   2 +-
 lib/{lib.error.c => lib.error.cc} | 128 +++++++++++++-----------------
 lib/lib.error.h                   |  14 +---
 5 files changed, 66 insertions(+), 92 deletions(-)
 rename lib/{lib.error.c => lib.error.cc} (69%)

diff --git a/judge/evict.cc b/judge/evict.cc
index cdc1f1b103..3d6cd134d3 100644
--- a/judge/evict.cc
+++ b/judge/evict.cc
@@ -14,9 +14,7 @@
 
 #include "lib.misc.h"
 
-extern "C" {
 #include "lib.error.h"
-}
 
 #define PROGRAM "evict"
 #define VERSION DOMJUDGE_VERSION "/" REVISION
diff --git a/judge/runguard.cc b/judge/runguard.cc
index 6cda4645b8..18ef5c2b7c 100644
--- a/judge/runguard.cc
+++ b/judge/runguard.cc
@@ -188,12 +188,12 @@ struct option const long_opts[] = {
 	{ nullptr,     0,                 nullptr,          0 }
 };
 
-void warning(   const char *, ...) __attribute__((format (printf, 1, 2)));
-void verbose(   const char *, ...) __attribute__((format (printf, 1, 2)));
-void error(int, const char *, ...) __attribute__((format (printf, 2, 3)));
+static void warning(   const char *, ...) __attribute__((format (printf, 1, 2)));
+static void verbose(   const char *, ...) __attribute__((format (printf, 1, 2)));
+static void error(int, const char *, ...) __attribute__((format (printf, 2, 3)));
 void write_meta(const char *, const char *, ...) __attribute__((format (printf, 2, 3)));
 
-void warning(const char *format, ...)
+static void warning(const char *format, ...)
 {
 	va_list ap;
 	va_start(ap,format);
@@ -207,7 +207,7 @@ void warning(const char *format, ...)
 	va_end(ap);
 }
 
-void verbose(const char *format, ...)
+static void verbose(const char *format, ...)
 {
 	va_list ap;
 	va_start(ap,format);
@@ -244,7 +244,7 @@ void warning_from_signalhandler(const char* msg)
 	}
 }
 
-void error(int errnum, const char *format, ...)
+static void error(int errnum, const char *format, ...)
 {
 	// Silently ignore errors that happen while handling other errors.
 	if (in_error_handling) return;
diff --git a/lib/Makefile b/lib/Makefile
index e608dbfba5..ae08cc68e8 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -8,7 +8,7 @@ OBJECTS = $(addsuffix $(OBJEXT),lib.error lib.misc)
 
 build: $(OBJECTS)
 
-lib.error$(OBJEXT): lib.error.c lib.error.h
+lib.error$(OBJEXT): lib.error.cc lib.error.h
 lib.misc$(OBJEXT): lib.misc.cc lib.misc.h
 
 clean-l:
diff --git a/lib/lib.error.c b/lib/lib.error.cc
similarity index 69%
rename from lib/lib.error.c
rename to lib/lib.error.cc
index 6ecee19198..c2cfdd40ab 100644
--- a/lib/lib.error.c
+++ b/lib/lib.error.cc
@@ -18,25 +18,17 @@
 
 #include "lib.error.h"
 
-#include <stdlib.h>
-#include <string.h>
+#include <cstdlib>
+#include <cstring>
+#include <cstdarg>
+#include <cstdio>
+#include <ctime>
+#include <vector>
+#include <string>
+#include <iostream>
 #include <unistd.h>
-#include <time.h>
 #include <sys/time.h>
 
-/* Define va_copy macro if not available (ANSI C99 only).
- * memcpy() is fallback suggested by the autoconf manual, but doesn't
- * work with g++ on AMD 64bit platform.
- * FIXME: Replace by autoconf test?
- */
-#ifndef va_copy
-#ifdef __va_copy
-#define va_copy(dest, src) __va_copy(dest,src)
-#else
-#define va_copy(dest, src) memcpy(&dest, &src, sizeof(va_list))
-#endif
-#endif
-
 /* Use program name in syslogging if defined */
 #ifndef PROGRAM
 #define PROGRAM NULL
@@ -52,22 +44,28 @@ int  loglevel     = LOG_DEBUG;
 FILE *stdlog      = NULL;
 int  syslog_open  = 0;
 
-char *printf_escape(const char *str)
+/* Escape '%' characters in a string for use in printf like functions */
+static std::string escape_percent(const char *str)
 {
-	char *escaped;
-	char c;
-	size_t str_pos, esc_pos;
+	if (str == NULL) return "";
+	std::string escaped;
+	size_t len = strlen(str);
+	size_t percent_count = 0;
+
+	for (size_t i = 0; i < len; ++i) {
+		if (str[i] == '%') {
+			percent_count++;
+		}
+	}
 
-	escaped = (char *)malloc(2*strlen(str)+1);
-	esc_pos = 0;
+	escaped.reserve(len + percent_count);
 
-	for(str_pos=0; str_pos<strlen(str); str_pos++) {
-		c = str[str_pos];
-		escaped[esc_pos++] = c;
-		if ( c=='%' ) escaped[esc_pos++] = c;
+	for (size_t i = 0; i < len; ++i) {
+		escaped += str[i];
+		if (str[i] == '%') {
+			escaped += '%';
+		}
 	}
-	escaped[esc_pos] = 0;
-
 	return escaped;
 }
 
@@ -77,9 +75,7 @@ void vlogmsg(int msglevel, const char *mesg, va_list ap)
 	struct timeval currtime;
 	struct tm tm_buf;
 	char timestring[128];
-	char *progname_escaped;
-	char *buffer;
-	int bufferlen;
+	std::string buffer;
 	va_list aq;
 	char *str, *endptr;
 	int syslog_fac;
@@ -106,37 +102,36 @@ void vlogmsg(int msglevel, const char *mesg, va_list ap)
 	strftime(timestring, sizeof(timestring), "%b %d %H:%M:%S", &tm_buf);
 	sprintf(timestring+strlen(timestring), ".%03d", (int)(currtime.tv_usec/1000));
 
-	progname_escaped = printf_escape(progname);
-	if ( progname_escaped==NULL ) abort();
-
-	bufferlen = strlen(timestring)+strlen(progname_escaped)+strlen(mesg)+20;
-	buffer = (char *)malloc(bufferlen);
-	if ( buffer==NULL ) abort();
+	std::string progname_escaped = escape_percent(progname);
 
-	snprintf(buffer, bufferlen, "[%s] %s[%d]: %s\n",
-	         timestring, progname_escaped, getpid(), mesg);
-
-	free(progname_escaped);
+	// Construct the format string: "[time] progname[pid]: message\n"
+	buffer = "[";
+	buffer += timestring;
+	buffer += "] ";
+	buffer += progname_escaped;
+	buffer += "[";
+	buffer += std::to_string(getpid());
+	buffer += "]: ";
+	buffer += mesg;
+	buffer += "\n";
 
 	if ( msglevel<=verbose ) {
 		va_copy(aq, ap);
-		vfprintf(stderr, buffer, aq);
+		vfprintf(stderr, buffer.c_str(), aq);
 		fflush(stderr);
 		va_end(aq);
 	}
 	if ( msglevel<=loglevel && stdlog!=NULL ) {
 		va_copy(aq, ap);
-		vfprintf(stdlog, buffer, aq);
+		vfprintf(stdlog, buffer.c_str(), aq);
 		fflush(stdlog);
 		va_end(aq);
 	}
 
-	free(buffer);
-
 	if ( msglevel<=loglevel && syslog_open ) {
-		buffer = vallocstr(mesg, ap);
-		syslog(msglevel, "%s", buffer);
-		free(buffer);
+		char *syslog_buf = vallocstr(mesg, ap);
+		syslog(msglevel, "%s", syslog_buf);
+		free(syslog_buf);
 	}
 }
 
@@ -161,47 +156,36 @@ void logmsg(int msglevel, const char *mesg, ...)
 */
 char *errorstring(const char *type, int errnum, const char *mesg)
 {
-	size_t buffersize;
-	char *errtype, *errdescr, *buffer;
+	std::string errtype;
+	std::string errdescr;
+	std::string buffer;
 
 	/* Set errtype to given string or default to 'ERROR' */
 	if ( type==NULL ) {
-		errtype = strdup(ERRSTR);
-		if ( errtype==NULL ) abort();
+		errtype = ERRSTR;
 	} else {
-		errtype = (char *)type;
+		errtype = type;
 	}
 
-	errdescr = NULL;
 	if ( errnum != 0 ) {
 		errdescr = strerror(errno);
 	} else if ( mesg == NULL ) {
-		errdescr = strdup("unknown error");
+		errdescr = "unknown error";
 	}
 
-	buffersize = strlen(errtype)
-	            + (errdescr == NULL ? 0 : strlen(errdescr))
-	            + (mesg == NULL     ? 0 : strlen(mesg))
-	            + 5;
-
-	buffer = (char *)malloc(sizeof(char) * buffersize);
-	if ( buffer==NULL ) abort();
-	buffer[0] = '\0';
-
-	strcat(buffer, errtype);
-	strcat(buffer, ": ");
+	buffer = errtype + ": ";
 
-	if ( mesg != NULL )     strcat(buffer, mesg);
+	if ( mesg != NULL )     buffer += mesg;
 
 	if ( mesg != NULL &&
-	     errdescr != NULL ) strcat(buffer, ": ");
+	     !errdescr.empty() ) buffer += ": ";
 
-	if ( errdescr != NULL )	strcat(buffer, errdescr);
+	if ( !errdescr.empty() ) buffer += errdescr;
 
-	if ( type == NULL ) free(errtype);
-	if ( mesg == NULL && errnum == 0 ) free(errdescr);
+	char *res = strdup(buffer.c_str());
+	if ( res==NULL ) abort();
 
-	return buffer;
+	return res;
 }
 
 /* Function to generate and write error logmessage (using vlogmsg) */
diff --git a/lib/lib.error.h b/lib/lib.error.h
index ffc2afc466..706e79d2b1 100644
--- a/lib/lib.error.h
+++ b/lib/lib.error.h
@@ -5,9 +5,9 @@
 #ifndef LIB_ERROR_H
 #define LIB_ERROR_H
 
-#include <stdarg.h>
-#include <stdio.h>
-#include <errno.h>
+#include <cstdarg>
+#include <cstdio>
+#include <cerrno>
 #ifdef HAVE_SYSLOG_H
 #include <syslog.h>
 #else
@@ -20,10 +20,6 @@
 #define WARNSTR   "warning"
 #define WARNMATCH WARNSTR": "
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 extern const int exit_failure;
 
 /* Import from the main program for logging purposes */
@@ -89,8 +85,4 @@ char *vallocstr(const char *, va_list);
  * Returns a pointer to the allocated string
  */
 
-#ifdef __cplusplus
-}
-#endif
-
 #endif /* LIB_ERROR_H */

From a21e83feafe99fc9078e6200542877f4c9600368 Mon Sep 17 00:00:00 2001
From: Tobias Werth <werth@cs.fau.de>
Date: Sun, 23 Nov 2025 16:07:50 +0100
Subject: [PATCH 4/5] Switch to C++20 and modernize formatting code.

---
 .github/jobs/configure-checks/all.bats |   2 +-
 configure.ac                           |   2 +-
 judge/evict.cc                         |  26 +--
 judge/runpipe.cc                       |  83 ++++-----
 lib/Makefile                           |   2 +-
 lib/lib.error.cc                       | 248 ++-----------------------
 lib/lib.error.h                        |  88 ---------
 lib/lib.error.hpp                      |  91 +++++++++
 lib/lib.misc.cc                        |   2 +-
 misc-tests/test_compare.sh             |   2 +-
 10 files changed, 170 insertions(+), 376 deletions(-)
 delete mode 100644 lib/lib.error.h
 create mode 100644 lib/lib.error.hpp

diff --git a/.github/jobs/configure-checks/all.bats b/.github/jobs/configure-checks/all.bats
index 0ac60eae40..2f94df4f81 100755
--- a/.github/jobs/configure-checks/all.bats
+++ b/.github/jobs/configure-checks/all.bats
@@ -106,7 +106,7 @@ compiler_assertions () {
 
 compile_assertions_finished () {
     assert_line " * CFLAGS..............: -g -O2 -Wall -Wformat -Wformat-security -pedantic -fstack-protector -fPIE -D_FORTIFY_SOURCE=2 -std=c11"
-    assert_line " * CXXFLAGS............: -g -O2 -Wall -Wformat -Wformat-security -pedantic -fstack-protector -fPIE -D_FORTIFY_SOURCE=2 -std=c++11"
+    assert_line " * CXXFLAGS............: -g -O2 -Wall -Wformat -Wformat-security -pedantic -fstack-protector -fPIE -D_FORTIFY_SOURCE=2 -std=c++20"
     assert_line " * LDFLAGS.............:  -fPIE -pie -Wl,-z,relro -Wl,-z,now"
 }
 
diff --git a/configure.ac b/configure.ac
index d75637c44b..fea76ebd0a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -72,7 +72,7 @@ if test "x$JUDGEHOST_BUILD_ENABLED" = xyes; then
 	AX_APPEND_LINK_FLAGS([-Wl,-z,now],   DEF_LDFLAGS)
 
 	test "x$enable_CFLAGS_setting"   = xyes && AC_SUBST(CFLAGS,   "$DEF_CXFLAGS -std=c11")
-	test "x$enable_CXXFLAGS_setting" = xyes && AC_SUBST(CXXFLAGS, "$DEF_CXFLAGS -std=c++11")
+	test "x$enable_CXXFLAGS_setting" = xyes && AC_SUBST(CXXFLAGS, "$DEF_CXFLAGS -std=c++20")
 	test "x$enable_LDFLAGS_setting"  = xyes && AC_SUBST(LDFLAGS,  $DEF_LDFLAGS)
 fi
 
diff --git a/judge/evict.cc b/judge/evict.cc
index 3d6cd134d3..fc72fc2255 100644
--- a/judge/evict.cc
+++ b/judge/evict.cc
@@ -14,13 +14,13 @@
 
 #include "lib.misc.h"
 
-#include "lib.error.h"
+#include "lib.error.hpp"
 
 #define PROGRAM "evict"
 #define VERSION DOMJUDGE_VERSION "/" REVISION
 
 extern int errno;
-const char *progname;
+std::string_view progname;
 
 int be_verbose;
 int show_help;
@@ -51,7 +51,7 @@ void evict_directory(const std::string& dirname) {
 
 	dir = opendir(dirname.c_str());
 	if (dir != NULL) {
-		if (be_verbose) logmsg(LOG_INFO, "Evicting all files in directory: %s", dirname.c_str());
+		if (be_verbose) logmsg(LOG_INFO, "Evicting all files in directory: {}", dirname);
 
 		/* Read everything in the directory */
 		while ( (entry = readdir(dir)) != NULL ) {
@@ -64,14 +64,14 @@ void evict_directory(const std::string& dirname) {
 			std::string entry_path = dirname + "/" + entry->d_name;
 			fd = open(entry_path.c_str(), O_RDONLY, 0);
 			if (fd == -1) {
-				warning(errno, "Unable to open file: %s", entry_path.c_str());
+				warning(errno, "Unable to open file: {}", entry_path);
 				continue;
 			}
 
 			if (fstat(fd, &s) < 0) {
-				if (be_verbose) logerror(errno, "Unable to stat file/directory: %s\n", entry_path.c_str());
+				if (be_verbose) logerror(errno, "Unable to stat file/directory: {}\n", entry_path);
 				if ( close(fd)!=0 ) {
-					warning(errno, "Unable to close file: %s", entry_path.c_str());
+					warning(errno, "Unable to close file: {}", entry_path);
 				}
 				continue;
 			}
@@ -81,21 +81,21 @@ void evict_directory(const std::string& dirname) {
 			} else {
 				/* evict this file from the cache */
 				if (posix_fadvise(fd, 0, 0, POSIX_FADV_DONTNEED)) {
-					warning(errno, "Unable to evict file: %s\n", entry_path.c_str());
+					warning(errno, "Unable to evict file: {}\n", entry_path);
 				} else {
-					if (be_verbose) logmsg(LOG_DEBUG, "Evicted file: %s", entry_path.c_str());
+					if (be_verbose) logmsg(LOG_DEBUG, "Evicted file: {}", entry_path);
 				}
 			}
 
 			if ( close(fd)!=0 ) {
-				warning(errno, "Unable to close file: %s", entry_path.c_str());
+				warning(errno, "Unable to close file: {}", entry_path);
 			}
 		}
 		if ( closedir(dir)!=0 ) {
-			warning(errno, "Unable to close directory: %s", dirname.c_str());
+			warning(errno, "Unable to close directory: {}", dirname);
 		}
 	} else {
-		warning(errno, "Unable to open directory: %s", dirname.c_str());
+		warning(errno, "Unable to open directory: {}", dirname);
 	}
 }
 
@@ -118,10 +118,10 @@ int main(int argc, char *argv[])
 			break;
 		case ':': /* getopt error */
 		case '?':
-			logmsg(LOG_ERR, "unknown option or missing argument `%c'", optopt);
+			logmsg(LOG_ERR, "unknown option or missing argument `{}`", (char)optopt);
 			break;
 		default:
-			logmsg(LOG_ERR, "getopt returned character code `%c' ??", (char)opt);
+			logmsg(LOG_ERR, "getopt returned character code `{}` ??", (char)opt);
 		}
 	}
 
diff --git a/judge/runpipe.cc b/judge/runpipe.cc
index be48667d6b..cb8849fb30 100644
--- a/judge/runpipe.cc
+++ b/judge/runpipe.cc
@@ -62,7 +62,7 @@
 
 #include "config.h"
 
-#include "lib.error.h"
+#include "lib.error.hpp"
 #include "lib.misc.h"
 
 #include <algorithm>
@@ -88,13 +88,13 @@ using namespace std;
 
 using fd_t = int;
 
-const char *progname;
+std::string_view progname;
 
 // Set the NONBLOCK flag for a file descriptor.
 void set_non_blocking(fd_t fd) {
   int flags = fcntl(fd, F_GETFL, 0);
   if (fcntl(fd, F_SETFL, flags | O_NONBLOCK)) {
-    error(errno, "failed to set fd %d to non blocking", fd);
+    error(errno, "failed to set fd {} to non blocking", fd);
   }
 }
 
@@ -117,28 +117,28 @@ void resize_pipe(int fd) {
     FILE *f = nullptr;
     if ((f = fopen(PROC_MAX_PIPE_SIZE, "r")) == nullptr) {
       max_pipe_size = FAILED;
-      warning(errno, "could not open '%s'", PROC_MAX_PIPE_SIZE);
+      warning(errno, "could not open '{}'", PROC_MAX_PIPE_SIZE);
       return;
     }
     if (fscanf(f, "%d", &max_pipe_size) != 1) {
       max_pipe_size = FAILED;
-      warning(errno, "could not read from '%s'", PROC_MAX_PIPE_SIZE);
+      warning(errno, "could not read from '{}'", PROC_MAX_PIPE_SIZE);
       if (fclose(f) != 0) {
-        warning(errno, "could not close '%s'", PROC_MAX_PIPE_SIZE);
+        warning(errno, "could not close '{}'", PROC_MAX_PIPE_SIZE);
       }
       return;
     }
     if (fclose(f) != 0) {
-      warning(errno, "could not close '%s'", PROC_MAX_PIPE_SIZE);
+      warning(errno, "could not close '{}'", PROC_MAX_PIPE_SIZE);
     }
   }
 
   int new_size = fcntl(fd, F_SETPIPE_SZ, max_pipe_size);
   if (new_size == -1) {
-    warning(errno, "could not change pipe size of %d", fd);
+    warning(errno, "could not change pipe size of {}", fd);
   }
 
-  logmsg(LOG_DEBUG, "set pipe fd %d to size %d", fd, new_size);
+  logmsg(LOG_DEBUG, "set pipe fd {} to size {}", fd, new_size);
 }
 
 // Write all the data into the file descriptor. It is assumed that the file
@@ -245,9 +245,9 @@ struct process_t {
 
     pid = execute(cmd, exec_args, stdio, false);
     if (pid < 0) {
-      error(errno, "failed to execute command #%ld", index);
+      error(errno, "failed to execute command #{}", index);
     }
-    logmsg(LOG_DEBUG, "started #%ld, pid %d", index, pid);
+    logmsg(LOG_DEBUG, "started #{}, pid {}", index, pid);
     // Do not leak these file descriptors, otherwise we cannot detect if the
     // process has closed stdout.
     close(stdin_fd);
@@ -264,7 +264,7 @@ struct process_t {
   // (i.e. proxy -> process).
   void close_input_fd() {
     if (proxy_to_process != -1) {
-      logmsg(LOG_DEBUG, "closing fd: %d (proxy -> process) of %d",
+      logmsg(LOG_DEBUG, "closing fd: {} (proxy -> process) of {}",
              proxy_to_process, pid);
       close(proxy_to_process);
     }
@@ -274,7 +274,7 @@ struct process_t {
   // (i.e. process -> proxy).
   void close_output_fd() {
     if (process_to_proxy != -1) {
-      logmsg(LOG_DEBUG, "closing fd: %d (process -> proxy) of %d",
+      logmsg(LOG_DEBUG, "closing fd: {} (process -> proxy) of {}",
              process_to_proxy, pid);
       close(process_to_proxy);
     }
@@ -318,7 +318,7 @@ struct output_file_t {
     output_file = open(path.c_str(), O_CREAT | O_CLOEXEC | O_WRONLY | O_TRUNC,
                        S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP);
     if (output_file == -1) {
-      error(errno, "failed to create proxy output file at %s", path.c_str());
+      error(errno, "failed to create proxy output file at {}", path);
     }
   }
 
@@ -362,7 +362,7 @@ struct output_file_t {
                  time_millis, size, direction);
     // Check that snprintf didn't truncate the header.
     if (header_len >= static_cast<int>(HEADER_SIZE)) {
-      error(0, "header size too small: %d > %ld", header_len, HEADER_SIZE);
+      error(0, "header size too small: {} > {}", header_len, HEADER_SIZE);
     }
 
     write_all(output_file, header, header_len);
@@ -376,7 +376,7 @@ void usage() {
 Usage: %s [OPTION]... COMMAND1 [ARGS...] = COMMAND2 [ARGS...]\n\
 Run two commands with stdin/stdout bi-directionally connected.\n\
 \n",
-         progname);
+         progname.data());
   printf("\
   -o, --outprog=FILE   write stdout from second program to FILE\n\
   -M, --outmeta=FILE   write metadata (runtime, exit_code, etc.) of first program to FILE\n\
@@ -456,22 +456,21 @@ struct state_t {
         break;
       case 'o': /* outprog option */
         args.output_file = optarg;
-        logmsg(LOG_DEBUG, "writing interactions to '%s'",
-               args.output_file.c_str());
+        logmsg(LOG_DEBUG, "writing interactions to '{}'", args.output_file);
         break;
       case 'M': /* outmeta option */
         args.meta_file = optarg;
-        logmsg(LOG_DEBUG, "writing metadata to '%s'", args.meta_file.c_str());
+        logmsg(LOG_DEBUG, "writing metadata to '{}'", args.meta_file);
         break;
       case 'h':
         args.show_help = 1;
         break;
       case ':': /* getopt error */
       case '?':
-        error(0, "unknown option or missing argument `%c'", optopt);
+        error(0, "unknown option or missing argument `{:c}'", optopt);
         break;
       default:
-        error(0, "getopt returned character code `%c' ??", (char)opt);
+        error(0, "getopt returned character code `{:c}' ??", opt);
       }
     }
 
@@ -534,7 +533,7 @@ struct state_t {
     if (args.verbose) {
       logmsg(LOG_DEBUG, "Processes:");
       for (size_t i = 0; i < processes.size(); i++) {
-        logmsg(LOG_DEBUG, "  #%ld: %s", i, processes[i].debug().c_str());
+        logmsg(LOG_DEBUG, "  #{}: {}", i, processes[i].debug());
       }
     }
   }
@@ -602,18 +601,18 @@ struct state_t {
     fd_t read_end = fds[0];
     static fd_t write_end = -1;
     if (write_end != -1) {
-      error(0, "attempted to install signal handler for %d twice", signum);
+      error(0, "attempted to install signal handler for {} twice", signum);
     }
     write_end = fds[1];
 
-    logmsg(LOG_DEBUG, "exit handler will send event using %d -> %d", write_end,
+    logmsg(LOG_DEBUG, "exit handler will send event using {} -> {}", write_end,
            read_end);
 
     signal(signum, [](int) {
       // TODO: Decide whether to keep some logging as the line below. We can't
       // use logmsg here since that will in turn call syslog which is not safe
       // to do in a signal handler (see also `man signal-safety`).
-      // logmsg(LOG_DEBUG, "caught signal %d", signum);
+      // logmsg(LOG_DEBUG, "caught signal {}", signum);
 
       // Notify the main loop that a child exited by sending a message via
       // the pipe.
@@ -668,21 +667,21 @@ struct state_t {
         // Use two pipes for the given direction with the
         // proxy in between.
         tie(read_end, write_end) = make_pipe();
-        logmsg(LOG_DEBUG, "setting up pipe #%ld (fd %d) -> proxy (fd %d)", i,
+        logmsg(LOG_DEBUG, "setting up pipe #{} (fd {}) -> proxy (fd {})", i,
                write_end, read_end);
         process.stdout_fd = write_end;
         process.process_to_proxy = read_end;
         set_non_blocking(process.process_to_proxy);
 
         tie(read_end, write_end) = make_pipe();
-        logmsg(LOG_DEBUG, "setting up pipe proxy (fd %d) -> #%ld (fd %d)",
+        logmsg(LOG_DEBUG, "setting up pipe proxy (fd {}) -> #{} (fd {})",
                write_end, j, read_end);
         other.proxy_to_process = write_end;
         other.stdin_fd = read_end;
       } else {
         // No proxy: direct communication.
         tie(read_end, write_end) = make_pipe();
-        logmsg(LOG_DEBUG, "setting up pipe #%ld (fd %d) -> #%ld (fd %d)", i,
+        logmsg(LOG_DEBUG, "setting up pipe #{} (fd {}) -> #{} (fd {})", i,
                write_end, j, read_end);
         process.stdout_fd = write_end;
         other.stdin_fd = read_end;
@@ -698,12 +697,12 @@ struct state_t {
     }
 
     auto add_fd = [&](fd_t fd) {
-      logmsg(LOG_DEBUG, "epoll will listen for fd %d", fd);
+      logmsg(LOG_DEBUG, "epoll will listen for fd {}", fd);
       epoll_event ev{};
       ev.data.fd = fd;
       ev.events = EPOLLIN;
       if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, fd, &ev)) {
-        error(errno, "failed to add fd %d to epoll", fd);
+        error(errno, "failed to add fd {} to epoll", fd);
       }
     };
 
@@ -751,7 +750,7 @@ struct state_t {
       return false;
     }
 
-    logmsg(LOG_DEBUG, "child with pid %d exited", pid);
+    logmsg(LOG_DEBUG, "child with pid {} exited", pid);
 
     // Only set the first process if runguard didn't tell us about a TLE.
     if (first_process_exit_id == -1 && !child_indicated_timelimit) {
@@ -777,7 +776,7 @@ struct state_t {
     }
 
     if (!found) {
-      error(0, "unknown child with pid %d exited", pid);
+      error(0, "unknown child with pid {} exited", pid);
     }
 
     return true;
@@ -811,7 +810,7 @@ struct state_t {
         sprintf(eofbuf, "[%3d.%03ds/%ld]%c", time_sec, time_millis, 0L, direction);
         write_all(output_file.output_file, eofbuf, strlen(eofbuf));
 
-        warning(0, "EOF from process #%ld", from.index);
+        warning(0, "EOF from process #{}", from.index);
         // The process closed stdout, we need to close the pipe's file
         // descriptors as well.
         to.close_input_fd();
@@ -823,7 +822,7 @@ struct state_t {
         if (errno == EAGAIN || errno == EWOULDBLOCK) {
           return;
         }
-        error(errno, "failed to read from pipe of #%ld", from.index);
+        error(errno, "failed to read from pipe of #{}", from.index);
       }
       // We've read nread bytes, write them to the other process' pipe.
       write_all(to.proxy_to_process, buffer, nread);
@@ -873,8 +872,8 @@ struct state_t {
           // happening and the communication with the other process may be very
           // broken.
           if (main_process().has_exited_with_signal()) {
-            logmsg(LOG_WARNING, "the first process crashed! %s",
-                   processes[0].exit_info_to_string().c_str());
+            logmsg(LOG_WARNING, "the first process crashed! {}",
+                   processes[0].exit_info_to_string());
           }
           continue;
         }
@@ -910,7 +909,7 @@ struct state_t {
   finish:
     logmsg(LOG_DEBUG, "all processes exited");
     if (!args.output_file.empty()) {
-      logmsg(LOG_INFO, "total communication amount: %ld KiB",
+      logmsg(LOG_INFO, "total communication amount: {} KiB",
              total_bytes_transferred / 1024);
     }
   }
@@ -925,7 +924,7 @@ struct state_t {
 
     ofstream meta(args.meta_file);
     if (meta.fail()) {
-      error(errno, "failed to open meta file at %s", args.meta_file.c_str());
+      error(errno, "failed to open meta file at {}", args.meta_file);
     }
     meta << "exitcode: " << main_process().exit_code() << endl;
     meta << "bytes-transferred: " << total_bytes_transferred << endl;
@@ -964,8 +963,8 @@ int main(int argc, char **argv) {
   if (state.args.verbose) {
     logmsg(LOG_DEBUG, "Exit statuses:");
     for (const auto &proc : state.processes) {
-      logmsg(LOG_DEBUG, "  #%ld: %s", proc.index,
-             proc.exit_info_to_string().c_str());
+      logmsg(LOG_DEBUG, "  #{}: {}", proc.index,
+             proc.exit_info_to_string());
     }
   }
 
@@ -977,6 +976,6 @@ int main(int argc, char **argv) {
   }
 
   // The first command exited with a signal.
-  error(0, "the first process crashed! %s",
-        main_process.exit_info_to_string().c_str());
+  error(0, "the first process crashed! {}",
+        main_process.exit_info_to_string());
 }
diff --git a/lib/Makefile b/lib/Makefile
index ae08cc68e8..0dabc2cb27 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -8,7 +8,7 @@ OBJECTS = $(addsuffix $(OBJEXT),lib.error lib.misc)
 
 build: $(OBJECTS)
 
-lib.error$(OBJEXT): lib.error.cc lib.error.h
+lib.error$(OBJEXT): lib.error.cc lib.error.hpp
 lib.misc$(OBJEXT): lib.misc.cc lib.misc.h
 
 clean-l:
diff --git a/lib/lib.error.cc b/lib/lib.error.cc
index c2cfdd40ab..5912bd0664 100644
--- a/lib/lib.error.cc
+++ b/lib/lib.error.cc
@@ -5,29 +5,20 @@
  * under the GNU GPL. See README and COPYING for details.
  */
 
-/* Implementation details:
- *
- * All argument-list based functions call their va_list (v..) counterparts
- * to avoid doubled code. Furthermore, all functions use 'vlogmsg' to do the
- * actual writing of the logmessage and all error/warning functions use
- * 'vlogerror' to generate the error-logmessage from the input. vlogerror in
- * turn calls errorstring to generate the actual error message;
- */
-
 #include "config.h"
 
-#include "lib.error.h"
+#include "lib.error.hpp"
 
 #include <cstdlib>
 #include <cstring>
 #include <cstdarg>
 #include <cstdio>
-#include <ctime>
 #include <vector>
 #include <string>
 #include <iostream>
+#include <fstream>
 #include <unistd.h>
-#include <sys/time.h>
+#include <chrono>
 
 /* Use program name in syslogging if defined */
 #ifndef PROGRAM
@@ -41,51 +32,21 @@ int  verbose      = LOG_NOTICE;
 int  loglevel     = LOG_DEBUG;
 
 /* Variables for tracking logging facilities */
-FILE *stdlog      = NULL;
+static std::ofstream stdlog;
 int  syslog_open  = 0;
 
-/* Escape '%' characters in a string for use in printf like functions */
-static std::string escape_percent(const char *str)
-{
-	if (str == NULL) return "";
-	std::string escaped;
-	size_t len = strlen(str);
-	size_t percent_count = 0;
-
-	for (size_t i = 0; i < len; ++i) {
-		if (str[i] == '%') {
-			percent_count++;
-		}
-	}
-
-	escaped.reserve(len + percent_count);
-
-	for (size_t i = 0; i < len; ++i) {
-		escaped += str[i];
-		if (str[i] == '%') {
-			escaped += '%';
-		}
-	}
-	return escaped;
-}
-
-/* Main function that contains logging code */
-void vlogmsg(int msglevel, const char *mesg, va_list ap)
+/* Core logging implementation that accepts a fully formatted string */
+void logmsg_str(int msglevel, const std::string& mesg)
 {
-	struct timeval currtime;
-	struct tm tm_buf;
-	char timestring[128];
 	std::string buffer;
-	va_list aq;
 	char *str, *endptr;
 	int syslog_fac;
 
-	/* This should never happen when called from any of the functions below. */
-	if ( mesg==NULL ) abort();
-
 	/* Try to open logfile if it is defined */
 #ifdef LOGFILE
-	if ( stdlog==NULL ) stdlog = fopen(LOGFILE,"a");
+	if (!stdlog.is_open()) {
+		stdlog.open(LOGFILE, std::ios::out | std::ios::app);
+	}
 #endif
 
 	/* Try to open syslog if it is defined */
@@ -97,194 +58,25 @@ void vlogmsg(int msglevel, const char *mesg, va_list ap)
 		}
 	}
 
-	gettimeofday(&currtime, NULL);
-	localtime_r(&currtime.tv_sec, &tm_buf);
-	strftime(timestring, sizeof(timestring), "%b %d %H:%M:%S", &tm_buf);
-	sprintf(timestring+strlen(timestring), ".%03d", (int)(currtime.tv_usec/1000));
-
-	std::string progname_escaped = escape_percent(progname);
+	auto now = std::chrono::system_clock::now();
+	auto millis = std::chrono::duration_cast<std::chrono::milliseconds>(now.time_since_epoch()) % 1000;
+	std::string timestring = std::format("{:%b %d %H:%M:%S}.{:03d}",
+			std::chrono::floor<std::chrono::seconds>(now), millis.count());
 
 	// Construct the format string: "[time] progname[pid]: message\n"
-	buffer = "[";
-	buffer += timestring;
-	buffer += "] ";
-	buffer += progname_escaped;
-	buffer += "[";
-	buffer += std::to_string(getpid());
-	buffer += "]: ";
+	buffer += "[" + timestring + "] ";
+	buffer += progname;
+	buffer += "[" + std::to_string(getpid()) + "]: ";
 	buffer += mesg;
-	buffer += "\n";
 
 	if ( msglevel<=verbose ) {
-		va_copy(aq, ap);
-		vfprintf(stderr, buffer.c_str(), aq);
-		fflush(stderr);
-		va_end(aq);
+		std::cerr << buffer << std::endl;
 	}
-	if ( msglevel<=loglevel && stdlog!=NULL ) {
-		va_copy(aq, ap);
-		vfprintf(stdlog, buffer.c_str(), aq);
-		fflush(stdlog);
-		va_end(aq);
+	if ( msglevel<=loglevel && stdlog.is_open() ) {
+		stdlog << buffer << std::endl;
 	}
 
 	if ( msglevel<=loglevel && syslog_open ) {
-		char *syslog_buf = vallocstr(mesg, ap);
-		syslog(msglevel, "%s", syslog_buf);
-		free(syslog_buf);
-	}
-}
-
-/* Argument-list wrapper function around vlogmsg */
-void logmsg(int msglevel, const char *mesg, ...)
-{
-	va_list ap;
-	va_start(ap, mesg);
-
-	vlogmsg(msglevel, mesg, ap);
-
-	va_end(ap);
-}
-
-/* Function to generate error/warning string:
-   - allocates memory for string (needs freeing later)
-   - generates message of the form:
-       errtype . ": " . mesg . ": " . errdescr
-     where 'errtype' can be "WARNING" / "ERROR"
-	 'mesg' is a program generated message (or NULL)
-	 'errnum' is the last system call's errno (or zero)
-*/
-char *errorstring(const char *type, int errnum, const char *mesg)
-{
-	std::string errtype;
-	std::string errdescr;
-	std::string buffer;
-
-	/* Set errtype to given string or default to 'ERROR' */
-	if ( type==NULL ) {
-		errtype = ERRSTR;
-	} else {
-		errtype = type;
+		syslog(msglevel, "%s", mesg.c_str());
 	}
-
-	if ( errnum != 0 ) {
-		errdescr = strerror(errno);
-	} else if ( mesg == NULL ) {
-		errdescr = "unknown error";
-	}
-
-	buffer = errtype + ": ";
-
-	if ( mesg != NULL )     buffer += mesg;
-
-	if ( mesg != NULL &&
-	     !errdescr.empty() ) buffer += ": ";
-
-	if ( !errdescr.empty() ) buffer += errdescr;
-
-	char *res = strdup(buffer.c_str());
-	if ( res==NULL ) abort();
-
-	return res;
-}
-
-/* Function to generate and write error logmessage (using vlogmsg) */
-void vlogerror(int errnum, const char *mesg, va_list ap)
-{
-	char *buffer;
-
-	buffer = errorstring(ERRSTR, errnum, mesg);
-
-	vlogmsg(LOG_ERR, buffer, ap);
-
-	free(buffer);
-}
-
-/* Argument-list wrapper function around vlogerror */
-void logerror(int errnum, const char *mesg, ...)
-{
-	va_list ap;
-	va_start(ap, mesg);
-
-	vlogerror(errnum, mesg, ap);
-
-	va_end(ap);
-}
-
-/* Logs an error message and exit with non-zero exitcode */
-void verror(int errnum, const char *mesg, va_list ap)
-{
-	vlogerror(errnum, mesg, ap);
-
-	exit(exit_failure);
-}
-
-/* Argument-list wrapper function around verror */
-void error(int errnum, const char *mesg, ...)
-{
-	va_list ap;
-	va_start(ap, mesg);
-
-	verror(errnum, mesg, ap);
-
-	va_end(ap);
-}
-
-/* Logs a warning message */
-void vwarning(int errnum, const char *mesg, va_list ap)
-{
-	char *buffer;
-
-	buffer = errorstring(WARNSTR, errnum, mesg);
-
-	vlogmsg(LOG_WARNING, buffer, ap);
-
-	free(buffer);
-}
-
-/* Argument-list wrapper function around vwarning */
-void warning(int errnum, const char *mesg, ...)
-{
-	va_list ap;
-	va_start(ap, mesg);
-
-	vwarning(errnum, mesg, ap);
-
-	va_end(ap);
-}
-
-/* Allocates a string with variable arguments */
-char *vallocstr(const char *mesg, va_list ap)
-{
-	char *str;
-	char tmp[2];
-	int len, n;
-	va_list aq;
-
-	va_copy(aq,ap);
-	len = vsnprintf(tmp,1,mesg,aq);
-	va_end(aq);
-
-	if ( (str = (char *) malloc(len+1))==NULL ) error(errno,"allocating string");
-
-	va_copy(aq,ap);
-	n = vsnprintf(str,len+1,mesg,aq);
-	va_end(aq);
-
-	if ( n==-1 || n>len ) error(0,"cannot write all of string");
-
-	return str;
-}
-
-/* Argument-list wrapper function around vallocstr */
-char *allocstr(const char *mesg, ...)
-{
-	va_list ap;
-	char *str;
-
-	va_start(ap,mesg);
-	str = vallocstr(mesg,ap);
-	va_end(ap);
-
-	return str;
 }
diff --git a/lib/lib.error.h b/lib/lib.error.h
deleted file mode 100644
index 706e79d2b1..0000000000
--- a/lib/lib.error.h
+++ /dev/null
@@ -1,88 +0,0 @@
-/*
- * Error handling and logging functions
- */
-
-#ifndef LIB_ERROR_H
-#define LIB_ERROR_H
-
-#include <cstdarg>
-#include <cstdio>
-#include <cerrno>
-#ifdef HAVE_SYSLOG_H
-#include <syslog.h>
-#else
-#error "Syslog header file not available."
-#endif
-
-#define ERRSTR    "error"
-#define ERRMATCH  ERRSTR": "
-
-#define WARNSTR   "warning"
-#define WARNMATCH WARNSTR": "
-
-extern const int exit_failure;
-
-/* Import from the main program for logging purposes */
-extern const char *progname;
-
-/* Variables defining logmessages verbosity to stderr/logfile */
-extern int  verbose;
-extern int  loglevel;
-extern FILE *stdlog;
-
-void  logmsg(int, const char *, ...) __attribute__((format (printf, 2, 3)));
-void vlogmsg(int, const char *, va_list);
-/* Logging functions (vlogmsg uses va_list instead of argument list):
- * Logs a message to stderr and/or logfile, including date and program name,
- * depending on the loglevel threshold values.
- *
- * Arguments:
- * int loglevel    syslog loglevel of this log-message
- * char *mesg      message, may include printf output format characters '%'
- * ... or va_list  optional arguments for format characters
- */
-
-char *errorstring(const char *, int, const char *);
-/* Error string generating function:
- * Returns a pointer to a dynamically allocated string containing the error
- * message.
- *
- * Arguments:
- * char *type      string of type of message: ERRSTR, WARNSTR or custom.
- * int errnum      'errno' value to use for error string output, set 0 to skip
- * char *mesg      optional accompanying message to display, set NULL to skip
- *
- * Returns a char pointer to the allocated string.
- */
-
-void logerror (int, const char *, ...) __attribute__((format (printf, 2, 3)));
-void error    (int, const char *, ...) __attribute__((format (printf, 2, 3), noreturn));
-void warning  (int, const char *, ...) __attribute__((format (printf, 2, 3)));
-void vlogerror(int, const char *, va_list) __attribute__((nonnull (2)));
-void verror   (int, const char *, va_list) __attribute__((nonnull (2), noreturn));
-void vwarning (int, const char *, va_list) __attribute__((nonnull (2)));
-/* Error and warning functions (v.. uses va_list instead of argument list):
- * Logs an error message including error string from 'errno'.
- *   logerror   only logs the error message (non-fatal error)
- *   error      log the message and exits with exit_failure
- *   warning    same as 'logerror', but prints 'warning' instead of 'error'
- *
- * Arguments:
- * int errnum      'errno' value to use for error string output, set 0 to skip
- * char *mesg      message, may include printf output format characters '%'
- * ... or va_list  optional arguments for format characters
- */
-
-char  *allocstr(const char *, ...) __attribute__((format (printf, 1, 2)));
-char *vallocstr(const char *, va_list);
-/* Create a c-string by allocating memory for it and writing to it,
- * using printf type format characters.
- *
- * Arguments:
- * char *mesg      message, may include printf output format characters '%'
- * ... or va_list  optional arguments for format characters
- *
- * Returns a pointer to the allocated string
- */
-
-#endif /* LIB_ERROR_H */
diff --git a/lib/lib.error.hpp b/lib/lib.error.hpp
new file mode 100644
index 0000000000..2439d9d81f
--- /dev/null
+++ b/lib/lib.error.hpp
@@ -0,0 +1,91 @@
+#ifndef LIB_ERROR_HPP
+#define LIB_ERROR_HPP
+
+#include <format>
+#include <string>
+#include <utility>
+#include <cstring>
+#include <cerrno>
+#include <cstdio>
+#include <cstdarg>
+#include <string_view>
+
+#ifdef HAVE_SYSLOG_H
+#include <syslog.h>
+#else
+#error "Syslog header file not available."
+#endif
+
+#define ERRSTR    "error"
+#define ERRMATCH  ERRSTR": "
+
+#define WARNSTR   "warning"
+#define WARNMATCH WARNSTR": "
+
+extern const int exit_failure;
+
+/* Import from the main program for logging purposes */
+extern std::string_view progname;
+
+/* Variables defining logmessages verbosity to stderr/logfile */
+extern int  verbose;
+extern int  loglevel;
+
+// Internal backend function (exposed for templates)
+void logmsg_str(int msglevel, const std::string& mesg);
+
+/**
+ * These functions accept std::format style strings and arguments.
+ * Example: logmsg(LOG_INFO, "Value: {}", 42);
+ */
+
+template<typename... Args>
+void logmsg(int level, std::format_string<Args...> fmt, Args&&... args) {
+    try {
+        std::string msg = std::format(fmt, std::forward<Args>(args)...);
+        logmsg_str(level, msg);
+    } catch (const std::format_error& e) {
+        logmsg_str(LOG_ERR, std::string("Format error in logmsg: ") + e.what());
+    }
+}
+
+// Helper for error/warning/logerror
+template<typename... Args>
+void log_helper(int level, const char* prefix, int errnum, std::format_string<Args...> fmt, Args&&... args) {
+    try {
+        std::string user_msg = std::format(fmt, std::forward<Args>(args)...);
+        std::string err_descr;
+        
+        if (errnum != 0) {
+            err_descr = std::strerror(errno);
+        }
+
+        std::string buffer;
+        if (prefix) buffer += prefix;
+        buffer += user_msg;
+        if (!user_msg.empty() && !err_descr.empty()) buffer += ": ";
+        if (!err_descr.empty()) buffer += err_descr;
+
+        logmsg_str(level, buffer);
+    } catch (const std::exception& e) {
+        logmsg_str(LOG_ERR, std::string("Format error: ") + e.what());
+    }
+}
+
+template<typename... Args>
+void error(int errnum, std::format_string<Args...> fmt, Args&&... args) {
+    log_helper(LOG_ERR, "error: ", errnum, fmt, std::forward<Args>(args)...);
+    std::exit(exit_failure);
+}
+
+template<typename... Args>
+void warning(int errnum, std::format_string<Args...> fmt, Args&&... args) {
+    log_helper(LOG_WARNING, "warning: ", errnum, fmt, std::forward<Args>(args)...);
+}
+
+template<typename... Args>
+void logerror(int errnum, std::format_string<Args...> fmt, Args&&... args) {
+    log_helper(LOG_ERR, "error: ", errnum, fmt, std::forward<Args>(args)...);
+}
+
+#endif // LIB_ERROR_HPP
diff --git a/lib/lib.misc.cc b/lib/lib.misc.cc
index 9a498001df..07c42872ba 100644
--- a/lib/lib.misc.cc
+++ b/lib/lib.misc.cc
@@ -18,7 +18,7 @@
 #include <iostream>
 
 #include "lib.misc.h"
-#include "lib.error.h"
+#include "lib.error.hpp"
 
 /* Array indices for input/output file descriptors as used by pipe() */
 constexpr int PIPE_IN = 1;
diff --git a/misc-tests/test_compare.sh b/misc-tests/test_compare.sh
index 297685e96d..b4200982b3 100755
--- a/misc-tests/test_compare.sh
+++ b/misc-tests/test_compare.sh
@@ -88,7 +88,7 @@ test_invalid_float_extra_chars() {
 
 any_test_failed=0
 
-g++ -g -O2 -Wall -std=c++17 ../sql/files/defaultdata/compare/compare.cc -o $COMPARE_EXECUTABLE
+g++ -g -O2 -Wall -std=c++20 ../sql/files/defaultdata/compare/compare.cc -o $COMPARE_EXECUTABLE
 
 for func in $(compgen -o nosort -A function test_); do
     fail=0

From bb44fe7fbc306db61e35f5d2ef45c352d1b1d7df Mon Sep 17 00:00:00 2001
From: Tobias Werth <werth@cs.fau.de>
Date: Thu, 27 Nov 2025 22:36:27 +0100
Subject: [PATCH 5/5] Use C++-style strings in runguard for logging.

---
 judge/runguard.cc | 449 +++++++++++++++++++++-------------------------
 lib/lib.error.hpp |   2 +-
 2 files changed, 201 insertions(+), 250 deletions(-)

diff --git a/judge/runguard.cc b/judge/runguard.cc
index 18ef5c2b7c..845a38b07f 100644
--- a/judge/runguard.cc
+++ b/judge/runguard.cc
@@ -29,11 +29,13 @@
 
 #include "config.h"
 
+#include "lib.error.hpp"
 #include "lib.misc.h"
 
 /* Some system/site specific config: VALID_USERS, CHROOT_PREFIX */
 #include "runguard-config.h"
 
+#include <iostream>
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <sys/param.h>
@@ -69,6 +71,7 @@
 #include <sstream>
 #include <string>
 #include <utility>
+#include <format>
 
 #define PROGRAM "runguard"
 #define VERSION DOMJUDGE_VERSION "/" REVISION
@@ -102,10 +105,9 @@ const struct timespec killdelay = { 0, 100000000L }; /* 0.1 seconds */
 const struct timespec cg_delete_delay = { 0, 10000000L }; /* 0.01 seconds */
 
 extern int errno;
+extern int verbose;
 
-const int exit_failure = -1;
-
-char  *progname;
+std::string_view progname;
 char  *cmdname;
 char **cmdargs;
 char  *rootdir;
@@ -135,8 +137,6 @@ int outputmeta;
 int outputtimetype;
 int no_coredump;
 int preserve_environment;
-int be_verbose;
-int be_quiet;
 int show_help;
 int show_version;
 int in_error_handling = 0;
@@ -188,71 +188,35 @@ struct option const long_opts[] = {
 	{ nullptr,     0,                 nullptr,          0 }
 };
 
-static void warning(   const char *, ...) __attribute__((format (printf, 1, 2)));
-static void verbose(   const char *, ...) __attribute__((format (printf, 1, 2)));
-static void error(int, const char *, ...) __attribute__((format (printf, 2, 3)));
-void write_meta(const char *, const char *, ...) __attribute__((format (printf, 2, 3)));
-
-static void warning(const char *format, ...)
-{
-	va_list ap;
-	va_start(ap,format);
-
-	if ( ! be_quiet ) {
-		fprintf(stderr,"%s: warning: ",progname);
-		vfprintf(stderr,format,ap);
-		fprintf(stderr,"\n");
-	}
-
-	va_end(ap);
-}
-
-static void verbose(const char *format, ...)
-{
-	va_list ap;
-	va_start(ap,format);
-
-	if ( ! be_quiet && be_verbose ) {
-        struct timeval currtime{};
-		gettimeofday(&currtime,nullptr);
-		double runtime = (currtime.tv_sec  - progstarttime.tv_sec ) +
-		                 (currtime.tv_usec - progstarttime.tv_usec)*1E-6;
-		fprintf(stderr,"%s [%d @ %10.6lf]: verbose: ",progname,getpid(),runtime);
-		vfprintf(stderr,format,ap);
-		fprintf(stderr,"\n");
-	}
-
-	va_end(ap);
-}
+template<typename... Args>
+void write_meta(const std::string& key, std::format_string<Args...> fmt, Args&&... args);
 
 // These functions are called from signal handlers, so they
 // must only call async-signal-safe functions.
 // write() is async-signal-safe, printf and variants are not.
 void verbose_from_signalhandler(const char* msg)
 {
-	if (!be_quiet && be_verbose) {
+	if (verbose >= LOG_DEBUG) {
 		[[maybe_unused]] auto r = write(STDERR_FILENO, msg, strlen(msg));
 	}
 }
 
 void warning_from_signalhandler(const char* msg)
 {
-	if (!be_quiet) {
+	if (verbose >= LOG_WARNING) {
 		// Do not include timing here, as it wouldn't be safe from a signalhandler.
 		// TODO: Consider rewriting using clock_gettime in the future.
 		[[maybe_unused]] auto r = write(STDERR_FILENO, msg, strlen(msg));
 	}
 }
 
-static void error(int errnum, const char *format, ...)
+template<typename... Args>
+void die(int errnum, std::format_string<Args...> fmt, Args&&... args)
 {
 	// Silently ignore errors that happen while handling other errors.
 	if (in_error_handling) return;
 	in_error_handling = 1;
 
-	va_list ap;
-	va_start(ap,format);
-
 	/*
 	 * Make sure the signal handler for these (terminate()) does not
 	 * interfere, we are exiting now anyway.
@@ -262,54 +226,43 @@ static void error(int errnum, const char *format, ...)
 	sigaddset(&sigs, SIGTERM);
 	sigprocmask(SIG_BLOCK, &sigs, nullptr);
 
-	/* First print to string to be able to reuse the message. */
-	size_t errlen = strlen(progname)+255;
-	if ( format!=nullptr ) errlen += strlen(format);
-
-	char *errstr = (char *)malloc(errlen);
-	if ( errstr==nullptr ) abort();
-
-	sprintf(errstr,"%s",progname);
-	size_t errpos = strlen(errstr);
-
-	if ( format!=nullptr ) {
-		snprintf(errstr+errpos,errlen-errpos,": ");
-		errpos += 2;
-		vsnprintf(errstr+errpos,errlen-errpos,format,ap);
-		errpos += strlen(errstr+errpos);
+	std::string errstr(progname);
+	errstr += ": ";
+	try {
+		errstr += std::format(fmt, std::forward<Args>(args)...);
+	} catch (const std::exception& e) {
+		errstr += "Error formatting error message: " + std::string(e.what());
 	}
-	if ( errnum!=0 ) {
+
+	if (errnum == 0) {
+		errstr += ": unknown error";
+	} else {
 		/* Special case libcgroup error codes. */
 		if ( errnum==ECGOTHER ) {
-			snprintf(errstr+errpos,errlen-errpos,": libcgroup");
-			errpos += strlen(errstr+errpos);
+			errstr += ": libcgroup";
 			errnum = errno;
 		}
 		if ( errnum>=ECGROUPNOTCOMPILED && errnum<=ECGROUPNOTCOMPILED ) {
-			snprintf(errstr+errpos,errlen-errpos,": %s",cgroup_strerror(errnum));
+			errstr += ": ";
+			errstr += cgroup_strerror(errnum);
 		} else {
-			snprintf(errstr+errpos,errlen-errpos,": %s",strerror(errnum));
+			errstr += ": ";
+			errstr += strerror(errnum);
 		}
-		errpos += strlen(errstr+errpos);
-	}
-	if ( format==nullptr && errnum==0 ) {
-		snprintf(errstr+errpos,errlen-errpos,": unknown error");
 	}
 
-	fprintf(stderr,"%s\nTry `%s --help' for more information.\n",errstr,progname);
-	va_end(ap);
+	std::cerr << errstr << std::endl;
 
-	write_meta("internal-error","%s",errstr);
+	write_meta("internal-error","{}", errstr);
 	if ( outputmeta && metafile != nullptr && fclose(metafile)!=0 ) {
 		fprintf(stderr,"\nError writing to metafile '%s'.\n",metafilename);
 	}
 
 	/* Make sure that all children are killed before terminating */
 	if ( child_pid > 0) {
-		verbose("sending SIGKILL");
+		logmsg(LOG_DEBUG, "sending SIGKILL");
 		if ( kill(-child_pid,SIGKILL)!=0 && errno!=ESRCH ) {
-			fprintf(stderr,"unable to send SIGKILL to children while terminating "
-					"due to previous error: %s\n", strerror(errno));
+			logmsg(LOG_ERR, "unable to send SIGKILL to children while terminating due to previous error: {}", strerror(errno));
 			/*
 			 * continue, there is not much we can do here.
 			 * In the worst case, this will trigger an error
@@ -325,27 +278,26 @@ static void error(int errnum, const char *format, ...)
 	exit(exit_failure);
 }
 
-void write_meta(const char *key, const char *format, ...)
+template<typename... Args>
+void write_meta(const std::string& key, std::format_string<Args...> fmt, Args&&... args)
 {
 	if ( !outputmeta ) return;
 
-	va_list ap;
-	va_start(ap,format);
-
-	if ( fprintf(metafile,"%s: ",key)<=0 ) {
-		outputmeta = 0;
-		error(0,"cannot write to file `%s'",metafilename);
-	}
-	if ( vfprintf(metafile,format,ap)<0 ) {
+	if ( fprintf(metafile,"%s: ",key.c_str())<=0 ) {
 		outputmeta = 0;
-		error(0,"cannot write to file `%s'(vfprintf)",metafilename);
+		die(0,"cannot write to file `{}'",metafilename);
 	}
-	if ( fprintf(metafile,"\n")<=0 ) {
+
+	try {
+		std::string value = std::format(fmt, std::forward<Args>(args)...);
+		if ( fprintf(metafile, "%s\n", value.c_str()) <= 0 ) {
+			outputmeta = 0;
+			die(0,"cannot write to file `{}'", metafilename);
+		}
+	} catch (const std::exception& e) {
 		outputmeta = 0;
-		error(0,"cannot write to file `%s'",metafilename);
+		die(0, "Error formatting meta value for key {}: {}", key, e.what());
 	}
-
-	va_end(ap);
 }
 
 void usage()
@@ -353,7 +305,7 @@ void usage()
 	printf("\
 Usage: %s [OPTION]... COMMAND...\n\
 Run COMMAND with restrictions.\n\
-\n", progname);
+\n", progname.data());
 	printf("\
   -r, --root=ROOT        run COMMAND with root directory set to ROOT\n\
   -u, --user=USER        run COMMAND as user with username or ID USER\n\
@@ -397,11 +349,11 @@ real user ID.\n");
 
 void output_exit_time(int exitcode, double cpudiff)
 {
-	verbose("command exited with exitcode %d",exitcode);
-	write_meta("exitcode","%d",exitcode);
+	logmsg(LOG_DEBUG, "command exited with exitcode {}",exitcode);
+	write_meta("exitcode","{}",exitcode);
 
 	if (received_signal != -1) {
-		write_meta("signal", "%d", received_signal);
+		write_meta("signal", "{}", (int)received_signal);
 	}
 
 	double walldiff = (endtime.tv_sec  - starttime.tv_sec ) +
@@ -411,22 +363,22 @@ void output_exit_time(int exitcode, double cpudiff)
 	double userdiff = (double)(endticks.tms_cutime - startticks.tms_cutime) / ticks_per_second;
 	double sysdiff  = (double)(endticks.tms_cstime - startticks.tms_cstime) / ticks_per_second;
 
-	write_meta("wall-time","%.3f", walldiff);
-	write_meta("user-time","%.3f", userdiff);
-	write_meta("sys-time", "%.3f", sysdiff);
-	write_meta("cpu-time", "%.3f", cpudiff);
+	write_meta("wall-time","{:.3f}", walldiff);
+	write_meta("user-time","{:.3f}", userdiff);
+	write_meta("sys-time", "{:.3f}", sysdiff);
+	write_meta("cpu-time", "{:.3f}", cpudiff);
 
-	verbose("runtime is %.3f seconds real, %.3f user, %.3f sys",
+	logmsg(LOG_DEBUG, "runtime is {:.3f} seconds real, {:.3f} user, {:.3f} sys",
 	        walldiff, userdiff, sysdiff);
 
 	if ( use_walltime && walldiff > walltimelimit[0] ) {
 		walllimit_reached |= soft_timelimit;
-		warning("timelimit exceeded (soft wall time)");
+		warning(0, "timelimit exceeded (soft wall time)");
 	}
 
 	if ( use_cputime && cpudiff > cputimelimit[0] ) {
 		cpulimit_reached |= soft_timelimit;
-		warning("timelimit exceeded (soft cpu time)");
+		warning(0, "timelimit exceeded (soft cpu time)");
 	}
 
 	int timelimit_reached = 0;
@@ -440,7 +392,7 @@ void output_exit_time(int exitcode, double cpudiff)
 		timelimit_reached = cpulimit_reached;
 		break;
 	default:
-		error(0,"cannot write unknown time type `%d' to file",outputtimetype);
+		die(0,"cannot write unknown time type `{}' to file",outputtimetype);
 	}
 
 	/* Hard limitlimit reached always has precedence. */
@@ -448,7 +400,7 @@ void output_exit_time(int exitcode, double cpudiff)
 		timelimit_reached |= hard_timelimit;
 	}
 
-	write_meta("time-result","%s",output_timelimit_str[timelimit_reached]);
+	write_meta("time-result","{}",output_timelimit_str[timelimit_reached]);
 }
 
 std::set<unsigned> parse_cpuset(std::string cpus)
@@ -464,14 +416,14 @@ std::set<unsigned> parse_cpuset(std::string cpus)
 			std::string token2 = token.substr(split+1);
 			size_t len;
 			unsigned cpu1 = std::stoul(token1, &len);
-			if ( len<token1.length() ) error(0, "failed to parse cpuset `%s'", cpus.c_str());
+			if ( len<token1.length() ) die(0, "failed to parse cpuset `{}'", cpus);
 			unsigned cpu2 = std::stoul(token2, &len);
-			if ( len<token2.length() ) error(0, "failed to parse cpuset `%s'", cpus.c_str());
+			if ( len<token2.length() ) die(0, "failed to parse cpuset `{}'", cpus);
 			for(unsigned i=cpu1; i<=cpu2; i++) result.insert(i);
 		} else {
 			size_t len;
 			unsigned cpu = std::stoul(token, &len);
-			if ( len<token.length() ) error(0, "failed to parse cpuset `%s'", cpus.c_str());
+			if ( len<token.length() ) die(0, "failed to parse cpuset `{}'", cpus);
 			result.insert(cpu);
 		}
 	}
@@ -482,15 +434,15 @@ std::set<unsigned> parse_cpuset(std::string cpus)
 std::set<unsigned> read_cpuset(const char *path)
 {
 	FILE *file = fopen(path, "r");
-	if (file == nullptr) error(errno, "opening file `%s'", path);
+	if (file == nullptr) die(errno, "opening file `{}'", path);
 
 	char cpuset[1024];
-	if (fgets(cpuset, 1024, file) == nullptr) error(errno, "reading from file `%s'", path);
+	if (fgets(cpuset, 1024, file) == nullptr) die(errno, "reading from file `{}'", path);
 
 	size_t len = strlen(cpuset);
 	if (len > 0 && cpuset[len-1] == '\n') cpuset[len-1] = 0;
 
-	if (fclose(file) != 0) error(errno, "closing file `%s'", path);
+	if (fclose(file) != 0) die(errno, "closing file `{}'", path);
 
 	return parse_cpuset(cpuset);
 }
@@ -502,50 +454,50 @@ void check_remaining_procs()
 
 	FILE *file = fopen(path, "r");
 	if (file == nullptr) {
-		error(errno, "opening cgroups file `%s'", path);
+		die(errno, "opening cgroups file `{}'", path);
 	}
 
 	fseek(file, 0L, SEEK_END);
 	if (ftell(file) > 0) {
-		error(0, "found left-over processes in cgroup controller, please check!");
+		die(0, "found left-over processes in cgroup controller, please check!");
 	}
-	if (fclose(file) != 0) error(errno, "closing file `%s'", path);
+	if (fclose(file) != 0) die(errno, "closing file `{}'", path);
 }
 
 
 void output_cgroup_stats(double *cputime)
 {
 	struct cgroup *cg;
-	if ( (cg = cgroup_new_cgroup(cgroupname))==nullptr ) error(0,"cgroup_new_cgroup");
+	if ( (cg = cgroup_new_cgroup(cgroupname))==nullptr ) die(0,"cgroup_new_cgroup");
 
 	int ret;
-	if ((ret = cgroup_get_cgroup(cg)) != 0) error(ret,"get cgroup information");
+	if ((ret = cgroup_get_cgroup(cg)) != 0) die(ret,"get cgroup information");
 
 	struct cgroup_controller *cg_controller = cgroup_get_controller(cg, "memory");
 	int64_t max_usage = 0;
 	ret = cgroup_get_value_int64(cg_controller, "memory.peak", &max_usage);
 	if ( ret == ECGROUPVALUENOTEXIST ) {
-		error(ret, "kernel too old and does not support memory.peak");
+		die(ret, "kernel too old and does not support memory.peak");
 	} else if ( ret!=0 ) {
-		error(ret,"get cgroup value memory.peak");
+		die(ret,"get cgroup value memory.peak");
 	}
 
 	// There is no need to check swap usage, as we limit it to 0.
-	verbose("total memory used: %" PRId64 " kB", max_usage/1024);
-	write_meta("memory-bytes","%" PRId64, max_usage);
+	logmsg(LOG_DEBUG, "total memory used: {} kB", max_usage/1024);
+	write_meta("memory-bytes","{}", max_usage);
 
 	struct cgroup_stat stat;
 	void *handle;
 	ret = cgroup_read_stats_begin("cpu", cgroupname, &handle, &stat);
 	while (ret == 0) {
-		verbose("cpu.stat: %s = %s", stat.name, stat.value);
+		logmsg(LOG_DEBUG, "cpu.stat: {} = {}", stat.name, stat.value);
 		if (strcmp(stat.name, "usage_usec") == 0) {
 			long long usec = strtoll(stat.value, nullptr, 10);
 			*cputime = usec / 1e6;
 		}
 		ret = cgroup_read_stats_next(&handle, &stat);
 	}
-	if ( ret!=ECGEOF ) error(ret,"get cgroup value cpu.stat");
+	if ( ret!=ECGEOF ) die(ret,"get cgroup value cpu.stat");
 	cgroup_read_stats_end(&handle);
 
 	cgroup_free(&cg);
@@ -554,19 +506,19 @@ void output_cgroup_stats(double *cputime)
 /* Temporary shorthand define for error handling. */
 #define cgroup_add_value(type,name,value) \
 	ret = cgroup_add_value_ ## type(cg_controller, name, value); \
-	if ( ret!=0 ) error(ret,"set cgroup value " #name);
+	if ( ret!=0 ) die(ret,"set cgroup value " #name);
 
 void cgroup_create()
 {
 	struct cgroup *cg;
 	cg = cgroup_new_cgroup(cgroupname);
-	if (!cg) error(0,"cgroup_new_cgroup");
+	if (!cg) die(0,"cgroup_new_cgroup");
 
 	/* Set up the memory restrictions; these two options limit ram use
 	   and ram+swap use. They are the same so no swapping can occur */
 	struct cgroup_controller *cg_controller;
 	if ( (cg_controller = cgroup_add_controller(cg, "memory"))==nullptr ) {
-		error(0,"cgroup_add_controller memory");
+		die(0,"cgroup_add_controller memory");
 	}
 
 	int ret;
@@ -584,7 +536,7 @@ void cgroup_create()
 	   no limits on memory nodes */
 	if ( cpuset!=nullptr && strlen(cpuset)>0 ) {
 		if ( (cg_controller = cgroup_add_controller(cg, "cpuset"))==nullptr ) {
-			error(0,"cgroup_add_controller cpuset");
+			die(0,"cgroup_add_controller cpuset");
 		}
 		/* To make a cpuset exclusive, some additional setup outside of domjudge is
 		   required, so for now, we will leave this commented out. */
@@ -592,14 +544,14 @@ void cgroup_create()
 		cgroup_add_value(string, "cpuset.mems", "0");
 		cgroup_add_value(string, "cpuset.cpus", cpuset);
 	} else {
-		verbose("cpuset undefined");
+		logmsg(LOG_DEBUG, "cpuset undefined");
 	}
 
 	/* Perform the actual creation of the cgroup */
-	if ( (ret = cgroup_create_cgroup(cg, 1))!=0 ) error(ret,"creating cgroup");
+	if ( (ret = cgroup_create_cgroup(cg, 1))!=0 ) die(ret,"creating cgroup");
 
 	cgroup_free(&cg);
-	verbose("created cgroup '%s'",cgroupname);
+	logmsg(LOG_DEBUG, "created cgroup `{}'",cgroupname);
 }
 
 #undef cgroup_setval
@@ -613,7 +565,7 @@ void cgroup_kill()
 	do {
 		pid_t* pids;
 		int ret = cgroup_get_procs(cgroupname, mem_controller, &pids, &size);
-		if (ret != 0) error(ret, "cgroup_get_procs");
+		if(ret != 0) die(ret, "cgroup_get_procs");
 		for(int i = 0; i < size; i++) {
 			kill(pids[i], SIGKILL);
 		}
@@ -625,23 +577,23 @@ void cgroup_delete()
 {
 	struct cgroup *cg;
 	cg = cgroup_new_cgroup(cgroupname);
-	if (!cg) error(0,"cgroup_new_cgroup");
+	if (!cg) die(0,"cgroup_new_cgroup");
 
-	if (cgroup_add_controller(cg, "cpu") == nullptr) error(0, "cgroup_add_controller cpu");
-	if ( cgroup_add_controller(cg, "memory")==nullptr ) error(0,"cgroup_add_controller memory");
+	if (cgroup_add_controller(cg, "cpu") == nullptr) die(0, "cgroup_add_controller cpu");
+	if ( cgroup_add_controller(cg, "memory")==nullptr ) die(0,"cgroup_add_controller memory");
 
 	if ( cpuset!=nullptr && strlen(cpuset)>0 ) {
-		if ( cgroup_add_controller(cg, "cpuset")==nullptr ) error(0,"cgroup_add_controller cpuset");
+		if ( cgroup_add_controller(cg, "cpuset")==nullptr ) die(0,"cgroup_add_controller cpuset");
 	}
 	/* Clean up our cgroup */
 	nanosleep(&cg_delete_delay,nullptr);
 	int ret = cgroup_delete_cgroup_ext(cg, CGFLAG_DELETE_IGNORE_MIGRATION | CGFLAG_DELETE_RECURSIVE);
 	// TODO: is this actually benign to ignore ECGOTHER here?
-	if ( ret!=0 && ret!=ECGOTHER ) error(ret,"deleting cgroup");
+	if ( ret!=0 && ret!=ECGOTHER ) die(ret,"deleting cgroup");
 
 	cgroup_free(&cg);
 
-	verbose("deleted cgroup '%s'",cgroupname);
+	logmsg(LOG_DEBUG, "deleted cgroup `{}'",cgroupname);
 }
 
 void terminate(int sig)
@@ -736,7 +688,7 @@ char *username()
 	struct passwd *pwd;
 	pwd = getpwuid(getuid());
 
-	if ( pwd==nullptr || errno ) error(errno,"failed to get username");
+	if ( pwd==nullptr || errno ) die(errno,"failed to get username");
 	errno = saved_errno;
 
 	return pwd->pw_name;
@@ -749,7 +701,7 @@ long read_optarg_int(const char *desc, long minval, long maxval)
 	errno = 0;
 	long arg = strtol(optarg,&ptr,10);
 	if ( errno || *ptr!='\0' || arg<minval || arg>maxval ) {
-		error(errno,"invalid %s specified: `%s'",desc,optarg);
+		die(errno,"invalid {} specified: `{}'",desc,optarg);
 	}
 
 	return arg;
@@ -758,7 +710,7 @@ long read_optarg_int(const char *desc, long minval, long maxval)
 void read_optarg_time(const char *desc, double *times)
 {
 	char *optcopy;
-	if ( (optcopy=strdup(optarg))==nullptr ) error(0,"strdup() failed");
+	if ( (optcopy=strdup(optarg))==nullptr ) die(0,"strdup() failed");
 
 	/* Check for soft:hard limit separator and cut string. */
 	char *sep;
@@ -768,7 +720,7 @@ void read_optarg_time(const char *desc, double *times)
 	errno = 0;
 	times[0] = strtod(optcopy,&ptr);
 	if ( errno || *ptr!='\0' || !finite(times[0]) || times[0]<=0 ) {
-		error(errno,"invalid %s specified: `%s'",desc,optarg);
+		die(errno,"invalid {} specified: `{}'",desc,optarg);
 	}
 
 	/* And repeat for hard limit if we found the ':' separator. */
@@ -776,10 +728,10 @@ void read_optarg_time(const char *desc, double *times)
 		errno = 0;
 		times[1] = strtod(sep+1,&ptr);
 		if ( errno || *(sep+1)=='\0' || *ptr!='\0' || !finite(times[1]) || times[1]<=0 ) {
-			error(errno,"invalid %s specified: `%s'",desc,optarg);
+			die(errno,"invalid {} specified: `{}'",desc,optarg);
 		}
 		if ( times[1]<times[0] ) {
-			error(0,"invalid %s specified: hard limit is lower than soft limit",desc);
+			die(0,"invalid {} specified: hard limit is lower than soft limit",desc);
 		}
 	} else {
 		/* Set soft and hard limits equal. */
@@ -806,7 +758,7 @@ void setrestrictions()
 		// strdup as putenv does not copy that string, but uses it as is.
 		char *token = strtok(strdup(tokens.c_str()), ";");
 		while (token != nullptr) {
-			verbose("setting environment variable: %s", token);
+			logmsg(LOG_DEBUG, "setting environment variable: {}", token);
 			putenv(token);
 			token = strtok(nullptr, ";");
 		}
@@ -820,9 +772,9 @@ void setrestrictions()
 #define setlim(type) \
 	if ( setrlimit(RLIMIT_ ## type, &lim)!=0 ) { \
 		if ( errno==EPERM ) { \
-			warning("no permission to set resource RLIMIT_" #type); \
+			warning(0, "no permission to set resource RLIMIT_" #type); \
 		} else { \
-			error(errno,"setting resource RLIMIT_" #type); \
+			die(errno,"setting resource RLIMIT_" #type); \
 		} \
 	}
 
@@ -835,7 +787,7 @@ void setrestrictions()
 		   not by default and gives us a reliable way to detect if the
 		   CPU-time limit was reached. */
 		rlim_t cputime_limit = (rlim_t)ceil(cputimelimit[1]);
-		verbose("setting hard CPU-time limit to %d(+1) seconds",(int)cputime_limit);
+		logmsg(LOG_DEBUG, "setting hard CPU-time limit to {}(+1) seconds",(int)cputime_limit);
 		lim.rlim_cur = cputime_limit;
 		lim.rlim_max = cputime_limit+1;
 		setlim(CPU);
@@ -851,13 +803,13 @@ void setrestrictions()
 	setlim(STACK);
 
 	if ( filesize!=RLIM_INFINITY ) {
-		verbose("setting filesize limit to %lu bytes",filesize);
+		logmsg(LOG_DEBUG, "setting filesize limit to {} bytes",filesize);
 		lim.rlim_cur = lim.rlim_max = filesize;
 		setlim(FSIZE);
 	}
 
 	if ( nproc!=RLIM_INFINITY ) {
-		verbose("setting process limit to %d",(int)nproc);
+		logmsg(LOG_DEBUG, "setting process limit to {}",(int)nproc);
 		lim.rlim_cur = lim.rlim_max = nproc;
 		setlim(NPROC);
 	}
@@ -865,77 +817,77 @@ void setrestrictions()
 #undef setlim
 
 	if ( no_coredump ) {
-		verbose("disabling core dumps");
+		logmsg(LOG_DEBUG, "disabling core dumps");
 		lim.rlim_cur = lim.rlim_max = 0;
-		if ( setrlimit(RLIMIT_CORE,&lim)!=0 ) error(errno,"disabling core dumps");
+		if ( setrlimit(RLIMIT_CORE,&lim)!=0 ) die(errno,"disabling core dumps");
 	}
 
 	/* Put the child process in the cgroup */
 	const char *controllers[] = { "memory", nullptr };
 	if (cgroup_change_cgroup_path(cgroupname, getpid(), controllers) != 0) {
-		error(0, "Failed to move the process to the cgroup");
+		die(0, "Failed to move the process to the cgroup");
 	}
 
 	/* Run the command in a separate process group so that the command
 	   and all its children can be killed off with one signal. */
-	if ( setsid()==-1 ) error(errno,"setsid failed");
+	if ( setsid()==-1 ) die(errno,"setsid failed");
 
 	/* Set root-directory and change directory to there. */
 	if ( use_root ) {
 		/* Small security issue: when running setuid-root, people can find
 		   out which directories exist from error message. */
-		if ( chdir(rootdir)!=0 ) error(errno,"cannot chdir to `%s'",rootdir);
+		if ( chdir(rootdir)!=0 ) die(errno,"cannot chdir to `{}'",rootdir);
 
 		/* Get absolute pathname of rootdir, by reading it. */
 		char  cwd[PATH_MAX+1];
-		if ( getcwd(cwd,PATH_MAX)==nullptr ) error(errno,"cannot get directory");
+		if ( getcwd(cwd,PATH_MAX)==nullptr ) die(errno,"cannot get directory");
 		if ( cwd[strlen(cwd)-1]!='/' ) strcat(cwd,"/");
 
 		/* Canonicalize CHROOT_PREFIX. */
 		char *path;
 		if ( (path = (char *) malloc(PATH_MAX+1))==nullptr ) {
-			error(errno,"allocating memory");
+			die(errno,"allocating memory");
 		}
 		if ( realpath(CHROOT_PREFIX,path)==nullptr ) {
-			error(errno,"cannot canonicalize path '%s'",CHROOT_PREFIX);
+			die(errno,"cannot canonicalize path `{}'",CHROOT_PREFIX);
 		}
 
 		/* Check that we are within prescribed path. */
 		if ( strncmp(cwd,path,strlen(path))!=0 ) {
-			error(0,"invalid root: must be within `%s'",path);
+			die(0,"invalid root: must be within `{}'",path);
 		}
 		free(path);
 
-		if ( chroot(".")!=0 ) error(errno,"cannot change root to `%s'",cwd);
-		if ( chdir("/")!=0 ) error(errno,"cannot chdir to `/' in chroot");
+		if ( chroot(".")!=0 ) die(errno,"cannot change root to `{}'",cwd);
+		if ( chdir("/")!=0 ) die(errno,"cannot chdir to `/' in chroot");
 		if ( rootchdir!=nullptr ) {
-			if ( chdir(rootchdir)!=0 ) error(errno,"cannot chdir to `%s' in chroot", rootchdir);
+			if ( chdir(rootchdir)!=0 ) die(errno,"cannot chdir to `{}' in chroot", rootchdir);
 		}
-		verbose("using root-directory `%s'",cwd);
+		logmsg(LOG_DEBUG, "using root-directory `{}'",cwd);
 	}
 
 	/* Set group-id (must be root for this, so before setting user). */
 	if ( use_group ) {
-		if ( setgid(rungid) ) error(errno,"cannot set group ID to `%d'",rungid);
-		if ( setgroups(0, nullptr) ) error(errno,"cannot clear auxiliary groups");
+		if ( setgid(rungid) ) die(errno,"cannot set group ID to `{}'",rungid);
+		if ( setgroups(0, nullptr) ) die(errno,"cannot clear auxiliary groups");
 
-		verbose("using group ID `%d'",rungid);
+		logmsg(LOG_DEBUG, "using group ID `{}'",rungid);
 	}
 	/* Set user-id (must be root for this). */
 	if ( use_user ) {
-		if ( setuid(runuid) ) error(errno,"cannot set user ID to `%d'",runuid);
-		verbose("using user ID `%d' for command",runuid);
+		if ( setuid(runuid) ) die(errno,"cannot set user ID to `{}'",runuid);
+		logmsg(LOG_DEBUG, "using user ID `{}' for command",runuid);
 	} else {
 		/* Permanently reset effective uid to real uid, to prevent
 		   child command from having root privileges.
 		   Note that this means that the child runs as the same user
 		   as the watchdog process and can thus manipulate it, e.g. by
 		   sending SIGSTOP/SIGCONT! */
-		if ( setuid(getuid()) ) error(errno,"cannot reset real user ID");
-		verbose("reset user ID to `%d' for command",getuid());
+		if ( setuid(getuid()) ) die(errno,"cannot reset real user ID");
+		logmsg(LOG_DEBUG, "reset user ID to `{}' for command",getuid());
 	}
 	if ( geteuid()==0 || getuid()==0 ) {
-		error(0,"root privileges not dropped. Do not run judgedaemon as root.");
+		die(0,"root privileges not dropped. Do not run judgedaemon as root.");
 	}
 }
 
@@ -968,7 +920,7 @@ void pump_pipes(fd_set* readfds, size_t data_read[], size_t data_passed[])
 
 					if ( nread==-1 && errno==EINVAL ) {
 						use_splice = 0;
-						verbose("splice failed, switching to read/write");
+						logmsg(LOG_DEBUG, "splice failed, switching to read/write");
 						/* Setting errno here to repeat the copy. */
 						errno = EAGAIN;
 					}
@@ -997,17 +949,17 @@ void pump_pipes(fd_set* readfds, size_t data_read[], size_t data_passed[])
 
 				/* print message if we're at the streamsize limit */
 				if (limit_streamsize && data_passed[i] == streamsize) {
-					verbose("child fd %i limit reached",i);
+					logmsg(LOG_DEBUG, "child fd {} limit reached",i);
 				}
 			}
 			if ( nread==-1 ) {
 				if (errno == EINTR || errno == EAGAIN || errno == EWOULDBLOCK) continue;
-				error(errno,"copying data fd %d",i);
+				die(errno,"copying data fd {}",i);
 			}
 			if ( nread==0 ) {
 				/* EOF detected: close fd and indicate this with -1 */
 				if ( close(child_pipefd[i][PIPE_OUT])!=0 ) {
-					error(errno,"closing pipe for fd %d",i);
+					die(errno,"closing pipe for fd {}",i);
 				}
 				child_pipefd[i][PIPE_OUT] = -1;
 				continue;
@@ -1035,7 +987,7 @@ int main(int argc, char **argv)
 
 	progname = argv[0];
 
-	if ( gettimeofday(&progstarttime,nullptr) ) error(errno,"getting time");
+	if ( gettimeofday(&progstarttime,nullptr) ) die(errno,"getting time");
 
 	/* Parse command-line options */
 	use_root = use_walltime = use_cputime = use_user = no_coredump = 0;
@@ -1044,7 +996,6 @@ int main(int argc, char **argv)
 	preserve_environment = 0;
 	memsize = filesize = nproc = RLIM_INFINITY;
 	redir_stdout = redir_stderr = limit_streamsize = 0;
-	be_verbose = be_quiet = 0;
 	show_help = show_version = 0;
 	opterr = 0;
 	char *ptr;
@@ -1055,38 +1006,38 @@ int main(int argc, char **argv)
 		case 'r': /* rootdir option */
 			use_root = 1;
 			rootdir = (char *) malloc(strlen(optarg)+2);
-			if ( rootdir==nullptr ) error(errno,"allocating memory");
+			if ( rootdir==nullptr ) die(errno,"allocating memory");
 			strcpy(rootdir,optarg);
 			break;
 		case 'u': /* user option: uid or string */
 			use_user = 1;
 			runuser = strdup(optarg);
-			if ( runuser==nullptr ) error(errno,"strdup() failed");
+			if ( runuser==nullptr ) die(errno,"strdup() failed");
 			errno = 0;
 			runuid = strtol(optarg,&ptr,10);
 			if ( errno || *ptr!='\0' ) {
 				runuid = userid(optarg);
 				if ( regcomp(&userregex,"^[A-Za-z][A-Za-z0-9\\._-]*$", REG_NOSUB)!=0 ) {
-					error(0,"could not create username regex");
+					die(0,"could not create username regex");
 				}
 				if ( regexec(&userregex, runuser, 0, nullptr, 0)!=0 ) {
-					error(0,"username `%s' does not match POSIX pattern", runuser);
+					die(0,"username `{}' does not match POSIX pattern", runuser);
 				}
 			}
-			if ( runuid<0 ) error(0,"invalid username or ID specified: `%s'",optarg);
+			if ( runuid<0 ) die(0,"invalid username or ID specified: `{}'",optarg);
 			break;
 		case 'g': /* group option: gid or string */
 			use_group = 1;
 			rungroup = strdup(optarg);
-			if ( rungroup==nullptr ) error(errno,"strdup() failed");
+			if ( rungroup==nullptr ) die(errno,"strdup() failed");
 			errno = 0;
 			rungid = strtol(optarg,&ptr,10);
 			if ( errno || *ptr!='\0' ) rungid = groupid(optarg);
-			if ( rungid<0 ) error(0,"invalid groupname or ID specified: `%s'",optarg);
+			if ( rungid<0 ) die(0,"invalid groupname or ID specified: `{}'",optarg);
 			break;
 		case 'd': /* chdir option */
 			rootchdir = (char *) malloc(strlen(optarg)+2);
-			if ( rootchdir==nullptr ) error(errno,"allocating memory");
+			if ( rootchdir==nullptr ) die(errno,"allocating memory");
 			strcpy(rootchdir,optarg);
 			break;
 		case 't': /* wallclock time option */
@@ -1155,46 +1106,46 @@ int main(int argc, char **argv)
 			metafilename = strdup(optarg);
 			break;
 		case 'v': /* verbose option */
-			be_verbose = 1;
+			verbose = LOG_DEBUG;
 			break;
 		case 'q': /* quiet option */
-			be_quiet = 1;
+			verbose = LOG_ERR;
 			break;
 		case 'U':
 			runpipe_pid = strtol(optarg, &ptr, 10);
 			break;
 		case ':': /* getopt error */
 		case '?':
-			error(0,"unknown option or missing argument `%c'",optopt);
+			die(0,"unknown option or missing argument `{}'",optopt);
 			break;
 		default:
-			error(0,"getopt returned character code `%c' ??",(char)opt);
+			die(0,"getopt returned character code `{:c}' ??",opt);
 		}
 	}
 
-	verbose("starting in verbose mode, PID = %d", getpid());
+	logmsg(LOG_DEBUG, "starting in verbose mode, PID = {}", getpid());
 
 	/* Make sure that we change from group root if we change to an
 	   unprivileged user to prevent unintended permissions. */
 	if ( use_user && !use_group ) {
-		verbose("using unprivileged user `%s' also as group",runuser);
+		logmsg(LOG_DEBUG, "using unprivileged user `{}' also as group",runuser);
 		use_group = 1;
 		rungroup = strdup(runuser);
 		rungid = groupid(rungroup);
-		if ( rungid<0 ) error(0,"invalid groupname or ID specified: `%s'",rungroup);
+		if ( rungid<0 ) die(0,"invalid groupname or ID specified: `{}'",rungroup);
 	}
 
 	if ( show_help ) usage();
 	if ( show_version ) version(PROGRAM,VERSION);
 
-	if ( argc<=optind ) error(0,"no command specified");
+	if ( argc<=optind ) die(0,"no command specified");
 
 	/* Command to be executed */
 	cmdname = argv[optind];
 	cmdargs = argv+optind;
 
 	if ( outputmeta && (metafile = fopen(metafilename,"w"))==nullptr ) {
-		error(errno,"cannot open `%s'",metafilename);
+		die(errno,"cannot open `{}'",metafilename);
 	}
 
 	/* Check that new uid is in list of valid uid's. When the new user
@@ -1209,26 +1160,26 @@ int main(int argc, char **argv)
 				ret = fnmatch(ptr,runuser,0);
 				if ( ret==0 ) break;
 				if ( ret!=FNM_NOMATCH ) {
-					error(0,"matching username `%s' against `%s'",runuser,ptr);
+					die(0,"matching username `{}' against `{}'",runuser,ptr);
 				}
 			}
 		}
-		if ( ptr==nullptr || runuid<=0 ) error(0,"illegal user specified: %d",runuid);
+		if ( ptr==nullptr || runuid<=0 ) die(0,"illegal user specified: {}",runuid);
 	}
 
 	/* Setup pipes connecting to child stdout/err streams (ignore stdin). */
 	for(int i=1; i<=2; i++) {
-		if ( pipe(child_pipefd[i])!=0 ) error(errno,"creating pipe for fd %d",i);
+		if ( pipe(child_pipefd[i])!=0 ) die(errno,"creating pipe for fd {}",i);
 	}
 
 	sigset_t emptymask;
-	if ( sigemptyset(&emptymask)!=0 ) error(errno,"creating empty signal mask");
+	if ( sigemptyset(&emptymask)!=0 ) die(errno,"creating empty signal mask");
 
 	/* unmask all signals, except SIGCHLD: detected in pselect() below */
 	sigset_t sigmask = emptymask;
-	if ( sigaddset(&sigmask, SIGCHLD)!=0 ) error(errno,"setting signal mask");
+	if ( sigaddset(&sigmask, SIGCHLD)!=0 ) die(errno,"setting signal mask");
 	if ( sigprocmask(SIG_SETMASK, &sigmask, nullptr)!=0 ) {
-		error(errno,"unmasking signals");
+		die(errno,"unmasking signals");
 	}
 
 	/* Construct signal handler for SIGCHLD detection in pselect(). */
@@ -1237,7 +1188,7 @@ int main(int argc, char **argv)
 	sigact.sa_flags   = 0;
 	sigact.sa_mask    = emptymask;
 	if ( sigaction(SIGCHLD,&sigact,nullptr)!=0 ) {
-		error(errno,"installing signal handler");
+		die(errno,"installing signal handler");
 	}
 
 	if ( cpuset!=nullptr && strlen(cpuset)>0 ) {
@@ -1246,7 +1197,7 @@ int main(int argc, char **argv)
 
 		for(unsigned cpu : cpus) {
 			if ( !online_cpus.count(cpu) ) {
-				error(0, "requested pinning on CPU %u which is not online", cpu);
+				die(0, "requested pinning on CPU {} which is not online", cpu);
 			}
 		}
 	}
@@ -1254,7 +1205,7 @@ int main(int argc, char **argv)
 	/* Make libcgroup ready for use */
 	ret = cgroup_init();
 	if ( ret!=0 ) {
-		error(0,"libcgroup initialization failed: %s(%d)\n", cgroup_strerror(ret), ret);
+		die(0,"libcgroup initialization failed: {}({})\n", cgroup_strerror(ret), ret);
 	}
 	/* Define the cgroup name that we will use and make sure it will
 	 * be unique. Note: group names must have slashes!
@@ -1270,7 +1221,7 @@ int main(int argc, char **argv)
 	cgroup_create();
 
 	if ( unshare(CLONE_FILES|CLONE_FS|CLONE_NEWIPC|CLONE_NEWNET|CLONE_NEWNS|CLONE_NEWUTS|CLONE_SYSVSEM)!=0 ) {
-		error(errno, "calling unshare");
+		die(errno, "calling unshare");
 	}
 
 	/* Check if any Linux Out-Of-Memory killer adjustments have to
@@ -1281,68 +1232,68 @@ int main(int argc, char **argv)
 	FILE *fp = nullptr;
 	const char *oom_score_path = "/proc/self/oom_score_adj";
 	if ( (fp = fopen(oom_score_path, "r+"))!=nullptr ) {
-		if ( fscanf(fp,"%d", &ret)!=1 ) error(errno,"cannot read from `%s'", oom_score_path);
+		if ( fscanf(fp,"%d", &ret)!=1 ) die(errno,"cannot read from `{}'", oom_score_path);
 		if ( ret<0 ) {
 			int oom_reset_value = 0;
-			verbose("resetting `%s' from %d to %d", oom_score_path, ret, oom_reset_value);
+			die(0, "resetting `{}' from {} to {}", oom_score_path, ret, oom_reset_value);
 			rewind(fp);
 			if ( fprintf(fp,"%d\n", oom_reset_value) <= 0 ) {
-				error(errno, "cannot write to `%s'", oom_score_path);
+				die(errno, "cannot write to `{}'", oom_score_path);
 			}
 		}
-		if ( fclose(fp)!=0 ) error(errno, "closing file `%s'", oom_score_path);
+		if ( fclose(fp)!=0 ) die(errno, "closing file `{}'", oom_score_path);
 	}
 
 	switch ( child_pid = fork() ) {
 	case -1: /* error */
-		error(errno,"cannot fork");
+		die(errno,"cannot fork");
 	case  0: /* run controlled command */
 		/* Apply all restrictions for child process. */
 		setrestrictions();
-		verbose("setrestrictions() done");
+		logmsg(LOG_DEBUG, "setrestrictions() done");
 
 		/* Connect pipes to command (stdin/)stdout/stderr and close
 		 * unneeded fd's. Do this after setting restrictions to let
 		 * any messages not go to command stderr pipe. */
 		for(int i=1; i<=2; i++) {
 			if ( dup2(child_pipefd[i][PIPE_IN],i)<0 ) {
-				error(errno,"redirecting child fd %d",i);
+				die(errno,"redirecting child fd {}",i);
 			}
 			if ( close(child_pipefd[i][PIPE_IN] )!=0 ||
 			     close(child_pipefd[i][PIPE_OUT])!=0 ) {
-				error(errno,"closing pipe for fd %d",i);
+				die(errno,"closing pipe for fd {}",i);
 			}
 		}
-		verbose("pipes closed in child");
+		logmsg(LOG_DEBUG, "pipes closed in child");
 
 		if ( outputmeta ) {
 			if ( fclose(metafile)!=0 ) {
-				error(errno,"closing file `%s'",metafilename);
+				die(errno,"closing file `{}'",metafilename);
 			}
-			verbose("metafile closed in child");
+			logmsg(LOG_DEBUG, "metafile closed in child");
 		}
 
 		/* And execute child command. */
 		execvp(cmdname,cmdargs);
-		error(errno,"cannot start `%s' as user `%s'", cmdname, username());
+		die(errno,"cannot start `{}' as user `{}'", cmdname, username());
 
 	default: /* become watchdog */
-		verbose("child pid = %d", child_pid);
+		logmsg(LOG_DEBUG, "child pid = {}", child_pid);
 		/* Shed privileges, only if not using a separate child uid,
 		   because in that case we may need root privileges to kill
 		   the child process. Do not use Linux specific setresuid()
 		   call with saved set-user-ID. */
 		if ( !use_user ) {
-			if ( setuid(getuid())!=0 ) error(errno, "setting watchdog uid");
-			verbose("watchdog using user ID `%d'",getuid());
+			if ( setuid(getuid())!=0 ) die(errno, "setting watchdog uid");
+			logmsg(LOG_DEBUG, "watchdog using user ID `{}'",getuid());
 		}
 
-		if ( gettimeofday(&starttime,nullptr) ) error(errno,"getting time");
+		if ( gettimeofday(&starttime,nullptr) ) die(errno,"getting time");
 
 		/* Close unused file descriptors */
 		for(int i=1; i<=2; i++) {
 			if ( close(child_pipefd[i][PIPE_IN])!=0 ) {
-				error(errno,"closing pipe for fd %i",i);
+				die(errno,"closing pipe for fd {}",i);
 			}
 		}
 
@@ -1355,24 +1306,24 @@ int main(int argc, char **argv)
 		if ( redir_stdout ) {
 			child_redirfd[STDOUT_FILENO] = creat(stdoutfilename, S_IRUSR | S_IWUSR);
 			if ( child_redirfd[STDOUT_FILENO]<0 ) {
-				error(errno,"opening file '%s'",stdoutfilename);
+				die(errno,"opening file `{}'",stdoutfilename);
 			}
 		}
 		if ( redir_stderr ) {
 			child_redirfd[STDERR_FILENO] = creat(stderrfilename, S_IRUSR | S_IWUSR);
 			if ( child_redirfd[STDERR_FILENO]<0 ) {
-				error(errno,"opening file '%s'",stderrfilename);
+				die(errno,"opening file `{}'",stderrfilename);
 			}
 		}
-		verbose("redirection done in parent");
+		logmsg(LOG_DEBUG, "redirection done in parent");
 
-		if ( sigemptyset(&emptymask)!=0 ) error(errno,"creating empty signal mask");
+		if ( sigemptyset(&emptymask)!=0 ) die(errno,"creating empty signal mask");
 
 		/* Construct one-time signal handler to terminate() for TERM
 		   and ALRM signals. */
 		sigset_t sigmask = emptymask;
 		if ( sigaddset(&sigmask,SIGALRM)!=0 ||
-		     sigaddset(&sigmask,SIGTERM)!=0 ) error(errno,"setting signal mask");
+		     sigaddset(&sigmask,SIGTERM)!=0 ) die(errno,"setting signal mask");
 
 		sigact.sa_handler = terminate;
 		sigact.sa_flags   = SA_RESETHAND | SA_RESTART;
@@ -1380,13 +1331,13 @@ int main(int argc, char **argv)
 
 		/* Kill child command when we receive SIGTERM */
 		if ( sigaction(SIGTERM,&sigact,nullptr)!=0 ) {
-			error(errno,"installing signal handler");
+			die(errno,"installing signal handler");
 		}
 
 		if ( use_walltime ) {
 			/* Kill child when we receive SIGALRM */
 			if ( sigaction(SIGALRM,&sigact,nullptr)!=0 ) {
-				error(errno,"installing signal handler");
+				die(errno,"installing signal handler");
 			}
 
 			/* Trigger SIGALRM via setitimer:  */
@@ -1396,13 +1347,13 @@ int main(int argc, char **argv)
 			itimer.it_value.tv_usec = (int)(modf(walltimelimit[1],&tmpd) * 1E6);
 
 			if ( setitimer(ITIMER_REAL,&itimer,nullptr)!=0 ) {
-				error(errno,"setting timer");
+				die(errno,"setting timer");
 			}
-			verbose("setting hard wall-time limit to %.3f seconds",walltimelimit[1]);
+			logmsg(LOG_DEBUG, "setting hard wall-time limit to {:.3f} seconds",walltimelimit[1]);
 		}
 
 		if ( times(&startticks)==(clock_t) -1 ) {
-			error(errno,"getting start clock ticks");
+			die(errno,"getting start clock ticks");
 		}
 
 		/* Wait for child data or exit.
@@ -1427,14 +1378,14 @@ int main(int argc, char **argv)
 			}
 
 			int r = pselect(nfds+1, &readfds, nullptr, nullptr, nullptr, &emptymask);
-			if ( r==-1 && errno!=EINTR ) error(errno,"waiting for child data");
+			if ( r==-1 && errno!=EINTR ) die(errno,"waiting for child data");
 			if (error_in_signalhandler) {
-				error(errno, "error in signal handler, exiting");
+				die(errno, "error in signal handler, exiting");
 			}
 
 			if ( received_SIGCHLD || received_signal == SIGALRM ) {
 				pid_t pid;
-				if ( (pid = wait(&status))<0 ) error(errno,"waiting on child");
+				if ( (pid = wait(&status))<0 ) die(errno,"waiting on child");
 				if ( pid==child_pid ) break;
 			}
 
@@ -1448,11 +1399,11 @@ int main(int argc, char **argv)
 				FD_SET(child_pipefd[i][PIPE_OUT],&readfds);
 				int r = fcntl(child_pipefd[i][PIPE_OUT], F_GETFL);
 				if (r == -1) {
-					error(errno, "fcntl, getting flags");
+					die(errno, "fcntl, getting flags");
 				}
 				r = fcntl(child_pipefd[i][PIPE_OUT], F_SETFL, r ^ O_NONBLOCK);
 				if (r == -1) {
-					error(errno, "fcntl, setting flags");
+					die(errno, "fcntl, setting flags");
 				}
 			}
 		}
@@ -1465,14 +1416,14 @@ int main(int argc, char **argv)
 		/* Close the output files */
 		for(int i=1; i<=2; i++) {
 			ret = close(child_redirfd[i]);
-			if( ret!=0 ) error(errno,"closing output fd %d", i);
+			if( ret!=0 ) die(errno,"closing output fd {}", i);
 		}
 
 		if ( times(&endticks)==(clock_t) -1 ) {
-			error(errno,"getting end clock ticks");
+			die(errno,"getting end clock ticks");
 		}
 
-		if ( gettimeofday(&endtime,nullptr) ) error(errno,"getting time");
+		if ( gettimeofday(&endtime,nullptr) ) die(errno,"getting time");
 
 		/* Test whether command has finished abnormally */
 		int exitcode = 0;
@@ -1480,22 +1431,22 @@ int main(int argc, char **argv)
 			if ( WIFSIGNALED(status) ) {
 				if ( WTERMSIG(status)==SIGXCPU ) {
 					cpulimit_reached |= hard_timelimit;
-					warning("timelimit exceeded (hard cpu time)");
+					warning(0, "timelimit exceeded (hard cpu time)");
 				} else {
-					warning("command terminated with signal %d",WTERMSIG(status));
+					warning(0, "command terminated with signal {}",WTERMSIG(status));
 				}
 				exitcode = 128+WTERMSIG(status);
 			} else
 			if ( WIFSTOPPED(status) ) {
-				warning("command stopped with signal %d",WSTOPSIG(status));
+				warning(0, "command stopped with signal {}",WSTOPSIG(status));
 				exitcode = 128+WSTOPSIG(status);
 			} else {
-				error(0,"command exit status unknown: %d",status);
+				die(0,"command exit status unknown: {}",status);
 			}
 		} else {
 			exitcode = WEXITSTATUS(status);
 		}
-		verbose("child exited with exit code %d", exitcode);
+		logmsg(LOG_DEBUG, "child exited with exit code {}", exitcode);
 
 		if ( use_walltime ) {
 			/* Disarm timer we set previously so if any of the
@@ -1507,7 +1458,7 @@ int main(int argc, char **argv)
 			itimer.it_value.tv_usec = 0;
 
 			if ( setitimer(ITIMER_REAL,&itimer,nullptr)!=0 ) {
-				error(errno,"disarming timer");
+				die(errno,"disarming timer");
 			}
 		}
 
@@ -1519,7 +1470,7 @@ int main(int argc, char **argv)
 		cgroup_delete();
 
 		/* Drop root before writing to output file(s). */
-		if ( setuid(getuid())!=0 ) error(errno,"dropping root privileges");
+		if ( setuid(getuid())!=0 ) die(errno,"dropping root privileges");
 
 		output_exit_time(exitcode, cputime);
 
@@ -1534,15 +1485,15 @@ int main(int argc, char **argv)
 				if ( ptr!=str ) ptr = stpcpy(ptr,",");
 				ptr = stpcpy(ptr,"stderr");
 			}
-			write_meta("output-truncated","%s",str);
+			write_meta("output-truncated","{}",str);
 		}
 
-		write_meta("stdin-bytes", "%zu",data_read[0]);
-		write_meta("stdout-bytes","%zu",data_read[1]);
-		write_meta("stderr-bytes","%zu",data_read[2]);
+		write_meta("stdin-bytes", "{}",data_read[0]);
+		write_meta("stdout-bytes","{}",data_read[1]);
+		write_meta("stderr-bytes","{}",data_read[2]);
 
 		if ( outputmeta && fclose(metafile)!=0 ) {
-			error(errno,"closing file `%s'",metafilename);
+			die(errno,"closing file `{}'",metafilename);
 		}
 
 		/* Return the exitstatus of the command */
@@ -1550,5 +1501,5 @@ int main(int argc, char **argv)
 	}
 
 	/* This should never be reached */
-	error(0,"unexpected end of program");
+	die(0,"unexpected end of program");
 }
diff --git a/lib/lib.error.hpp b/lib/lib.error.hpp
index 2439d9d81f..72dc48421b 100644
--- a/lib/lib.error.hpp
+++ b/lib/lib.error.hpp
@@ -57,7 +57,7 @@ void log_helper(int level, const char* prefix, int errnum, std::format_string<Ar
         std::string err_descr;
         
         if (errnum != 0) {
-            err_descr = std::strerror(errno);
+            err_descr = std::strerror(errnum);
         }
 
         std::string buffer;