compat: add canonicalize_file_name

the POSIX 2008 behaviour of realpath is not available everywhere so we
provide a simple wrapper function.  We use (and provide) the gnu
extension canonicalize_file_name to make it cleaner to test for the
feature we need; otherwise we have to rely on realpath segfaulting if
the second argument is null.

1 files changed, 18 insertions, 0 deletions

diff --git a/compat/canonicalize_file_name.c b/compat/canonicalize_file_name.c
new file mode 100644
index 00000000..e92c0f62
--- /dev/null
+++ b/compat/canonicalize_file_name.c
@@ -0,0 +1,18 @@
+#include "compat.h"
+#include <limits.h>
+#undef _GNU_SOURCE
+#include <stdlib.h>
+
+char *
+canonicalize_file_name (const char * path)
+{
+#ifdef PATH_MAX
+    char *resolved_path =  malloc (PATH_MAX+1);
+    if (resolved_path == NULL)
+	return NULL;
+
+    return realpath (path, resolved_path);
+#else
+#error undefined PATH_MAX _and_ missing canonicalize_file_name not supported
+#endif
+}