[PATCH] detect dup failure

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).

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..ca54387 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)
+			die("failed to duplicate standard output");
+		realstdout = fdopen(fd, "w");
+	}

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

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

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.