From 6cf6bb3e47ac2f667fa0b27a4222e903ff6fb77c Mon Sep 17 00:00:00 2001
From: Arnout Engelen <arnouten@bzzt.net>
Date: Sat, 18 Dec 2010 22:28:00 +0100
Subject: Improve error messages when temporary file creation fails

Before, when creating a temporary file failed, a generic 'Unable to create
temporary file' message was printed. In some cases this could lead to
confusion as to which directory should be checked for correct permissions etc.

This patch adds the template for the temporary filename to the error message,
converting it to an absolute path if needed. A test verifies that the template
is indeed printed when pointing to a nonexistent or unwritable directory.

A copy of the original template is made in case mkstemp clears the template.

Signed-off-by: Arnout Engelen <arnouten@bzzt.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Makefile b/Makefile
index 57d9c65..03a51cb 100644
--- a/Makefile
+++ b/Makefile
@@ -434,6 +434,7 @@ TEST_PROGRAMS_NEED_X += test-string-pool
 TEST_PROGRAMS_NEED_X += test-svn-fe
 TEST_PROGRAMS_NEED_X += test-treap
 TEST_PROGRAMS_NEED_X += test-index-version
+TEST_PROGRAMS_NEED_X += test-mktemp
 
 TEST_PROGRAMS = $(patsubst %,%$X,$(TEST_PROGRAMS_NEED_X))
 
diff --git a/t/t0070-fundamental.sh b/t/t0070-fundamental.sh
index 680d7d6..9bee8bf 100755
--- a/t/t0070-fundamental.sh
+++ b/t/t0070-fundamental.sh
@@ -12,4 +12,17 @@ test_expect_success 'character classes (isspace, isalpha etc.)' '
 	test-ctype
 '
 
+test_expect_success 'mktemp to nonexistent directory prints filename' '
+	test_must_fail test-mktemp doesnotexist/testXXXXXX 2>err &&
+	grep "doesnotexist/test" err
+'
+
+test_expect_success POSIXPERM 'mktemp to unwritable directory prints filename' '
+	mkdir cannotwrite &&
+	chmod -w cannotwrite &&
+	test_when_finished "chmod +w cannotwrite" &&
+	test_must_fail test-mktemp cannotwrite/testXXXXXX 2>err &&
+	grep "cannotwrite/test" err
+'
+
 test_done
diff --git a/test-mktemp.c b/test-mktemp.c
new file mode 100644
index 0000000..c8c5421
--- /dev/null
+++ b/test-mktemp.c
@@ -0,0 +1,14 @@
+/*
+ * test-mktemp.c: code to exercise the creation of temporary files
+ */
+#include "git-compat-util.h"
+
+int main(int argc, char *argv[])
+{
+	if (argc != 2)
+		usage("Expected 1 parameter defining the temporary file template");
+
+	xmkstemp(xstrdup(argv[1]));
+
+	return 0;
+}
diff --git a/wrapper.c b/wrapper.c
index 8d7dd31..55b074e 100644
--- a/wrapper.c
+++ b/wrapper.c
@@ -198,10 +198,22 @@ FILE *xfdopen(int fd, const char *mode)
 int xmkstemp(char *template)
 {
 	int fd;
+	char origtemplate[PATH_MAX];
+	strlcpy(origtemplate, template, sizeof(origtemplate));
 
 	fd = mkstemp(template);
-	if (fd < 0)
-		die_errno("Unable to create temporary file");
+	if (fd < 0) {
+		int saved_errno = errno;
+		const char *nonrelative_template;
+
+		if (!template[0])
+			template = origtemplate;
+
+		nonrelative_template = make_nonrelative_path(template);
+		errno = saved_errno;
+		die_errno("Unable to create temporary file '%s'",
+			nonrelative_template);
+	}
 	return fd;
 }
 
@@ -321,10 +333,22 @@ int gitmkstemps(char *pattern, int suffix_len)
 int xmkstemp_mode(char *template, int mode)
 {
 	int fd;
+	char origtemplate[PATH_MAX];
+	strlcpy(origtemplate, template, sizeof(origtemplate));
 
 	fd = git_mkstemp_mode(template, mode);
-	if (fd < 0)
-		die_errno("Unable to create temporary file");
+	if (fd < 0) {
+		int saved_errno = errno;
+		const char *nonrelative_template;
+
+		if (!template[0])
+			template = origtemplate;
+
+		nonrelative_template = make_nonrelative_path(template);
+		errno = saved_errno;
+		die_errno("Unable to create temporary file '%s'",
+			nonrelative_template);
+	}
 	return fd;
 }
 
-- 
cgit v0.10.2-6-g49f6