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.

4 files changed, 40 insertions, 0 deletions

diff --git a/compat/Makefile.local b/compat/Makefile.local
index b0d5417f..bcb9f0ec 100644
--- a/compat/Makefile.local
+++ b/compat/Makefile.local
@@ -5,6 +5,10 @@ extra_cflags += -I$(srcdir)/$(dir)
 
 notmuch_compat_srcs :=
 
+ifneq ($(HAVE_CANONICALIZE_FILE_NAME),1)
+notmuch_compat_srcs += $(dir)/canonicalize_file_name.c
+endif
+
 ifneq ($(HAVE_GETLINE),1)
 notmuch_compat_srcs += $(dir)/getline.c $(dir)/getdelim.c
 endif
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
+}
diff --git a/compat/compat.h b/compat/compat.h
index 5a402d5c..634d505b 100644
--- a/compat/compat.h
+++ b/compat/compat.h
@@ -37,6 +37,14 @@ extern "C" {
 #define _POSIX_PTHREAD_SEMANTICS 1
 #endif
 
+#if !HAVE_CANONICALIZE_FILE_NAME
+/* we only call this function from C, and this makes testing easier */
+#ifndef __cplusplus
+char *
+canonicalize_file_name (const char *path);
+#endif
+#endif
+
 #if !HAVE_GETLINE
 #include <stdio.h>
 #include <unistd.h>
diff --git a/compat/have_canonicalize_file_name.c b/compat/have_canonicalize_file_name.c
new file mode 100644
index 00000000..24c848ec
--- /dev/null
+++ b/compat/have_canonicalize_file_name.c
@@ -0,0 +1,10 @@
+#define _GNU_SOURCE
+#include <stdlib.h>
+
+int main()
+{
+    char *found;
+    char *string;
+
+    found = canonicalize_file_name (string);
+}