Add --with-system-libsafec flag to link against system libsafec

Specifying the --with-system-libsafec flag shall allow the configuration
program to search for and, if found, to link against the libsafec library
that is installed in the system.

After configuring --with-system-libsafec, the compilation will may with
following error:

In file included from /usr/include/libsafec/safe_lib.h:43,
                  from est_server_http.c:39:
/usr/include/libsafec/safe_types.h:42:9: error: unknown type name 'size_t'
   42 | typedef size_t  rsize_t;
      |         ^~~~~~

The system libsafec lacks including stddef.h in its safe_types.h.

Fix that by moving libsafec include directives below the openssl; the latter apparently
does the inclusion of the necessary stddef.h at some point.

Signed-off-by: Aleksandr Makarov <aleksandr.o.makarov@gmail.com>

Author: Aleksandr Makarov

Makefile.am

@@ -12,5 +12,9 @@ examples = example/client example/client-simple example/client-brski example/ser
 endif
 endif
 
-SUBDIRS = safe_c_stub src $(libest_jni) $(examples)
+if ! WITH_SYSTEM_LIBSAFEC
+builtin_libsafec = safe_c_stub
+endif
+
+SUBDIRS = $(builtin_libsafec) src $(libest_jni) $(examples)
 EXTRA_DIST = autogen.sh example/util LICENSE README.brski $(srcdir)/build.gradle $(srcdir)/example/build_examples.gradle

configure.ac

@@ -10,6 +10,7 @@ AM_INIT_AUTOMAKE([subdir-objects])
 
 AC_PROG_CC
 AM_PROG_CC_C_O
+PKG_PROG_PKG_CONFIG
 LT_INIT
 AC_CANONICAL_HOST
 case $host in
@@ -187,22 +188,39 @@ AC_ARG_WITH([libcoap-dir],
         ]
        )
 
-SAFEC_STUB_DIR='$(abs_top_builddir)/safe_c_stub'
-AC_SUBST(SAFEC_STUB_DIR)
-safecdir="$SAFEC_STUB_DIR" 
-AC_SUBST([SAFEC_DIR], "$safecdir")
-AC_SUBST([SAFEC_CFLAGS], "$safecdir/include")
-AC_SUBST([SAFEC_LDFLAGS], "$safecdir/lib")
+AC_ARG_WITH(system-libsafec,
+            AS_HELP_STRING([--with-system-libsafec],
+                           [select to use libsafec installed in the system]),
+            [],
+            [with_system_libsafec="no"])
 
-CFLAGS="$CFLAGS -Wall -I$safecdir/include"
-LDFLAGS="$LDFLAGS -L$safecdir/lib"
-LIBS="$LIBS -lsafe_lib"
+AC_MSG_CHECKING(which libsafec to use)
+AM_CONDITIONAL([WITH_SYSTEM_LIBSAFEC], [test "$with_system_libsafec" = "yes"])
+AM_COND_IF([WITH_SYSTEM_LIBSAFEC], AC_MSG_RESULT([system]), AC_MSG_RESULT([built-in]))
+AM_COND_IF([WITH_SYSTEM_LIBSAFEC],
+[
+           PKG_CHECK_MODULES([libsafec], [libsafec])
+           LIBS="$LIBS $libsafec_LIBS"
+           CFLAGS="$CFLAGS $libsafec_CFLAGS"
+           CPPFLAGS="$CPPFLAGS $libsafec_CFLAGS"
+],[
+           SAFEC_STUB_DIR='$(abs_top_builddir)/safe_c_stub'
+           AC_SUBST(SAFEC_STUB_DIR)
+           safecdir="$SAFEC_STUB_DIR"
+           AC_SUBST([SAFEC_DIR], "$safecdir")
+           AC_SUBST([SAFEC_CFLAGS], "$safecdir/include")
+           AC_SUBST([SAFEC_LDFLAGS], "$safecdir/lib")
+
+           CFLAGS="$CFLAGS -Wall -I$safecdir/include"
+           LDFLAGS="$LDFLAGS -L$safecdir/lib"
+           LIBS="$LIBS -lsafe_lib"
+])
 
 AC_PREFIX_DEFAULT([/usr/local/est])
 
 cp confdefs.h est_config.h
 
-AC_CONFIG_FILES([Makefile version safe_c_stub/Makefile safe_c_stub/lib/Makefile src/Makefile src/est/Makefile])
+AC_CONFIG_FILES([Makefile version src/Makefile src/est/Makefile])
 AM_COND_IF([ENABLE_JNI],
            [AC_CONFIG_FILES([java/jni/Makefile])])
 AM_COND_IF([ENABLE_EXAMPLES],
@@ -212,5 +230,8 @@ AM_COND_IF([ENABLE_EXAMPLES],
                        [],
                        [AC_CONFIG_FILES([example/server/Makefile example/proxy/Makefile])])
 ])
+AM_COND_IF([WITH_SYSTEM_LIBSAFEC],
+           [],
+           [AC_CONFIG_FILES([safe_c_stub/Makefile safe_c_stub/lib/Makefile])])
 
 AC_OUTPUT

src/est/est_server_http.c

@@ -36,15 +36,15 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 // THE SOFTWARE.
 
-#include "safe_lib.h"
-#include "safe_str_lib.h"
-#include "safe_mem_lib.h"
 #ifdef WIN32
 #include <WS2tcpip.h>
 #endif 
 #include <openssl/err.h>
 #include <openssl/ssl.h>
 #include <openssl/x509v3.h>
+#include "safe_lib.h"
+#include "safe_str_lib.h"
+#include "safe_mem_lib.h"
 #if defined(_WIN32)
 #define _CRT_SECURE_NO_WARNINGS // Disable deprecation warning in VS2005
 #else