git-log: detect dup and fdopen failure

This defines xdup() and xfdopen() in git-compat-util.h to give
us error-catching variants of them without cluttering the code
too much.
Signed-off-by: NJim Meyering <jim@meyering.net>
Acked-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

builtin-log.c

@@ -589,7 +589,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 		get_patch_ids(&rev, &ids, prefix);
 
 	if (!use_stdout)
-		realstdout = fdopen(dup(1), "w");
+		realstdout = xfdopen(xdup(1), "w");
 
 	prepare_revision_walk(&rev);
 	while ((commit = get_revision(&rev)) != NULL) {

git-compat-util.h

@@ -287,6 +287,22 @@ static inline ssize_t xwrite(int fd, const void *buf, size_t len)
 	}
 }
 
+static inline int xdup(int fd)
+{
+	int ret = dup(fd);
+	if (ret < 0)
+		die("dup failed: %s", strerror(errno));
+	return ret;
+}
+
+static inline FILE *xfdopen(int fd, const char *mode)
+{
+	FILE *stream = fdopen(fd, mode);
+	if (stream == NULL)
+		die("Out of memory? fdopen failed: %s", strerror(errno));
+	return stream;
+}
+
 static inline size_t xsize_t(off_t len)
 {
 	return (size_t)len;