[PATCH] git-log: detect dup and fdopen failure

"Alex Riesen" [off-list ref] wrote:

On 6/27/07, Jim Meyering [off-list ref] wrote:

quoted

Without this, if you ever run out of file descriptors, dup will
fail (silently), fdopen will return NULL, and fprintf will
try to dereference NULL (i.e., usually segfault).

But if you check the result of fdopen for NULL instead
you'll cover the dup failure _and_ out-of-memory in one
go. You'll loose the errno (probably), but you don't seem
to use it here anyway.

Good catch.  Thanks!
I didn't see that fdopen could fail with ENOMEM.
That'll teach me to trust the man page.  I see POSIX does mention it.

Here's a better patch:

Signed-off-by: Jim Meyering <redacted>
---
 builtin-log.c |    8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/builtin-log.c b/builtin-log.c
index 073a2a1..7b0d6f4 100644
--- a/builtin-log.c
+++ b/builtin-log.c

@@ -588,8 +588,12 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 	if (ignore_if_in_upstream)
 		get_patch_ids(&rev, &ids, prefix);

-	if (!use_stdout)
-		realstdout = fdopen(dup(1), "w");
+	if (!use_stdout) {
+		int fd = dup(1);
+		if (fd < 0 || (realstdout = fdopen(fd, "w")) == NULL)
+			die("failed to duplicate standard output: %s",
+			    strerror(errno));
+	}

 	prepare_revision_walk(&rev);
 	while ((commit = get_revision(&rev)) != NULL) {