From 5fdbaa76ad7bac67098dc7d72ad50fef5aeacec7 Mon Sep 17 00:00:00 2001
From: Eli Lipsitz <eli.lipsitz@gmail.com>
Date: Thu, 1 Oct 2020 08:28:16 -0700
Subject: [PATCH 1/2] Adjust %p formatting of non-NULL pointers to match glibc

This means prefixing with `0x` and using lowercase hex letters.
---
 printf.c            |  4 ++--
 test/test_suite.cpp | 16 ++++++++--------
 2 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/printf.c b/printf.c
index 8a700add..9f080684 100644
--- a/printf.c
+++ b/printf.c
@@ -820,8 +820,8 @@ static int _vsnprintf(out_fct_type out, char* buffer, const size_t maxlen, const
       }
 
       case 'p' : {
-        width = sizeof(void*) * 2U;
-        flags |= FLAGS_ZEROPAD | FLAGS_UPPERCASE;
+        width = sizeof(void*) * 2U + 2;
+        flags |= FLAGS_ZEROPAD | FLAGS_HASH;
 #if defined(PRINTF_SUPPORT_LONG_LONG)
         const bool is_ll = sizeof(uintptr_t) == sizeof(long long);
         if (is_ll) {
diff --git a/test/test_suite.cpp b/test/test_suite.cpp
index 5507c3bd..70c8ddc0 100644
--- a/test/test_suite.cpp
+++ b/test/test_suite.cpp
@@ -1361,35 +1361,35 @@ TEST_CASE("pointer", "[]" ) {
 
   test::sprintf(buffer, "%p", (void*)0x1234U);
   if (sizeof(void*) == 4U) {
-    REQUIRE(!strcmp(buffer, "00001234"));
+    REQUIRE(!strcmp(buffer, "0x00001234"));
   }
   else {
-    REQUIRE(!strcmp(buffer, "0000000000001234"));
+    REQUIRE(!strcmp(buffer, "0x0000000000001234"));
   }
 
   test::sprintf(buffer, "%p", (void*)0x12345678U);
   if (sizeof(void*) == 4U) {
-    REQUIRE(!strcmp(buffer, "12345678"));
+    REQUIRE(!strcmp(buffer, "0x12345678"));
   }
   else {
-    REQUIRE(!strcmp(buffer, "0000000012345678"));
+    REQUIRE(!strcmp(buffer, "0x0000000012345678"));
   }
 
   test::sprintf(buffer, "%p-%p", (void*)0x12345678U, (void*)0x7EDCBA98U);
   if (sizeof(void*) == 4U) {
-    REQUIRE(!strcmp(buffer, "12345678-7EDCBA98"));
+    REQUIRE(!strcmp(buffer, "0x12345678-0x7edcba98"));
   }
   else {
-    REQUIRE(!strcmp(buffer, "0000000012345678-000000007EDCBA98"));
+    REQUIRE(!strcmp(buffer, "0x0000000012345678-0x000000007edcba98"));
   }
 
   if (sizeof(uintptr_t) == sizeof(uint64_t)) {
     test::sprintf(buffer, "%p", (void*)(uintptr_t)0xFFFFFFFFU);
-    REQUIRE(!strcmp(buffer, "00000000FFFFFFFF"));
+    REQUIRE(!strcmp(buffer, "0x00000000ffffffff"));
   }
   else {
     test::sprintf(buffer, "%p", (void*)(uintptr_t)0xFFFFFFFFU);
-    REQUIRE(!strcmp(buffer, "FFFFFFFF"));
+    REQUIRE(!strcmp(buffer, "0xffffffff"));
   }
 }
 

From 729dd392e370c917f3905f38cd59473131add823 Mon Sep 17 00:00:00 2001
From: Eli Lipsitz <eli.lipsitz@gmail.com>
Date: Thu, 1 Oct 2020 09:44:03 -0700
Subject: [PATCH 2/2] Adjust %p formatting of NULL pointers to match glibc

This means printing "(nil)" instead of "0".
---
 printf.c            | 23 +++++++++++++++--------
 test/test_suite.cpp |  3 +++
 2 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/printf.c b/printf.c
index 9f080684..4c662fb4 100644
--- a/printf.c
+++ b/printf.c
@@ -822,18 +822,25 @@ static int _vsnprintf(out_fct_type out, char* buffer, const size_t maxlen, const
       case 'p' : {
         width = sizeof(void*) * 2U + 2;
         flags |= FLAGS_ZEROPAD | FLAGS_HASH;
+        uintptr_t value = (uintptr_t)va_arg(va, void*);
+
+        if (value == 0) {
+          idx = _out_rev(out, buffer, idx, maxlen, ")lin(", 5, width, flags);
+        } else {
 #if defined(PRINTF_SUPPORT_LONG_LONG)
-        const bool is_ll = sizeof(uintptr_t) == sizeof(long long);
-        if (is_ll) {
-          idx = _ntoa_long_long(out, buffer, idx, maxlen, (uintptr_t)va_arg(va, void*), false, 16U, precision, width, flags);
-        }
-        else {
+          const bool is_ll = sizeof(uintptr_t) == sizeof(long long);
+          if (is_ll) {
+            idx = _ntoa_long_long(out, buffer, idx, maxlen, value, false, 16U, precision, width, flags);
+          }
+          else {
 #endif
-          idx = _ntoa_long(out, buffer, idx, maxlen, (unsigned long)((uintptr_t)va_arg(va, void*)), false, 16U, precision, width, flags);
+            idx = _ntoa_long(out, buffer, idx, maxlen, (unsigned long)value, false, 16U, precision, width, flags);
 #if defined(PRINTF_SUPPORT_LONG_LONG)
-        }
+          }
 #endif
-        format++;
+        }
+
+        format++; 
         break;
       }
 
diff --git a/test/test_suite.cpp b/test/test_suite.cpp
index 70c8ddc0..740771ad 100644
--- a/test/test_suite.cpp
+++ b/test/test_suite.cpp
@@ -1391,6 +1391,9 @@ TEST_CASE("pointer", "[]" ) {
     test::sprintf(buffer, "%p", (void*)(uintptr_t)0xFFFFFFFFU);
     REQUIRE(!strcmp(buffer, "0xffffffff"));
   }
+
+  test::sprintf(buffer, "%p", nullptr);
+  REQUIRE(!strcmp(buffer, "(nil)"));
 }