build: make strerror() override-able

If we want to override `strerror()` in libjson-c
to make tests consistent across platforms, we
need to do it build-wide as configure/build
option.

Apple linkers make it really hard to override functions
at link-time, and this seems to be locked down on travis-ci.org
[ for security reasons I assume ].
While I got it to work locally, it did not work
when running on travis.

Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>

Makefile.am

@@ -53,6 +53,12 @@ libjson_c_la_SOURCES = \
 	printbuf.c \
 	random_seed.c
 
+if ENABLE_STRERROR_OVERRIDE
+libjson_cinclude_HEADERS+= \
+	strerror_override.h
+libjson_c_la_SOURCES+= \
+	strerror_override.c
+endif
 
 distclean-local:
 	-rm -rf $(testsubdir)

configure.ac

@@ -23,6 +23,22 @@ else
   AC_MSG_RESULT([RDRAND Hardware RNG Hash Seed disabled. Use --enable-rdrand to enable])
 fi
 
+AC_ARG_ENABLE(strerror-override,
+ AS_HELP_STRING([--enable-strerror-override],
+   [Override strerror() function with internal version.]),
+[if test x$enableval = xyes; then
+  enable_strerror_override=yes
+  AC_DEFINE(ENABLE_STRERROR_OVERRIDE, 1, [Override strerror() with internal version])
+fi])
+
+AM_CONDITIONAL([ENABLE_STRERROR_OVERRIDE], [test "x$enable_strerror_override" = "xyes"])
+
+if test "x$enable_strerror_override" = "xyes"; then
+  AC_MSG_RESULT([Overriding `strerror()` function with internal version])
+else
+  AC_MSG_RESULT([Using libc's `strerror()` function])
+fi
+
 # enable silent build by default
 m4_ifdef([AM_SILENT_RULES], [AM_SILENT_RULES([yes])])
 

json_object.c

@@ -12,13 +12,14 @@
 
 #include "config.h"
 
+#include "strerror_override.h"
+
 #include <assert.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <stddef.h>
 #include <string.h>
 #include <math.h>
-#include <errno.h>
 
 #include "debug.h"
 #include "printbuf.h"

json_pointer.c

@@ -8,10 +8,11 @@
 
 #include "config.h"
 
+#include "strerror_override.h"
+
 #include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
-#include <errno.h>
 #include <string.h>
 #include <ctype.h>
 

json_util.c

@@ -12,13 +12,14 @@
 #include "config.h"
 #undef realloc
 
+#include "strerror_override.h"
+
 #include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <stddef.h>
 #include <limits.h>
 #include <string.h>
-#include <errno.h>
 #include <ctype.h>
 
 #ifdef HAVE_SYS_TYPES_H

random_seed.c

@@ -9,6 +9,7 @@
  *
  */
 
+#include "strerror_override.h"
 #include <stdio.h>
 #include "config.h"
 #include "random_seed.h"
@@ -128,7 +129,6 @@ retry:
 #include <string.h>
 #include <fcntl.h>
 #include <unistd.h>
-#include <errno.h>
 #include <stdlib.h>
 #include <sys/stat.h>
 

strerror_override.c

@@ -1,4 +1,4 @@
-#include <errno.h>
+#include "strerror_override.h"
 
 /*
  * Override strerror() to get consistent output across platforms.
@@ -54,7 +54,7 @@ static struct {
 
 #define PREFIX "ERRNO="
 static char errno_buf[128] = PREFIX;
-char *strerror(int errno_in)
+char *_json_c_strerror(int errno_in)
 {
 	int start_idx;
 	char digbuf[20];

strerror_override.h

@@ -0,0 +1,12 @@
+#ifndef __STRERROR_OVERRIDE_H__
+#define __STRERROR_OVERRIDE_H__
+
+#include "config.h"
+#include <errno.h>
+
+#if ENABLE_STRERROR_OVERRIDE
+char *_json_c_strerror(int errno_in);
+#define strerror	_json_c_strerror
+#endif
+
+#endif /* __STRERROR_OVERRIDE_H__ */ 

tests/Makefile.am

@@ -52,7 +52,7 @@ EXTRA_DIST+= test2Formatted_plain.expected
 EXTRA_DIST+= test2Formatted_pretty.expected
 EXTRA_DIST+= test2Formatted_spaced.expected
 
-test_util_file_SOURCES = test_util_file.c strerror_override.c
+test_util_file_SOURCES = test_util_file.c
 
 testsubdir=testSubDir
 TESTS_ENVIRONMENT       = top_builddir=$(top_builddir)

tests/test_json_pointer.c

@@ -1,4 +1,4 @@
-#include <errno.h>
+#include "strerror_override.h"
 #include <assert.h>
 #include <stdio.h>
 #include <string.h>

tests/test_util_file.c

@@ -1,4 +1,4 @@
-#include <errno.h>
+#include "strerror_override.h"
 #include <stdio.h>
 #include <stdlib.h>
 #include <stddef.h>