From 9953eb926862c7461292dde38e2a666d715f249d Mon Sep 17 00:00:00 2001 From: Jim Meyering Date: Tue, 15 Apr 2025 18:44:55 -0700 Subject: [PATCH] close-stream: don't clobber errno upon prior failure MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Don't reset errno when fclose succeeds yet there was a preceding error. * lib/close-stream.c (close_stream): Don't clobber errno if prev_fail is true. Exposed via Fedora 42's new glibc vs grep's --help being precisely 4096 bytes. Reported by Jaroslav Škarvada in https://bugs.gnu.org/77800 --- ChangeLog | 8 ++++++++ lib/close-stream.c | 18 +++++++++--------- 2 files changed, 17 insertions(+), 9 deletions(-) diff --git a/ChangeLog b/ChangeLog index 6df7b09a1e..77960a4993 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,11 @@ +2025-04-15 Jim Meyering + + close-stream: don't clobber errno upon prior failure + Don't reset errno when fclose succeeds yet there was a preceding error. + * lib/close-stream.c (close_stream): Don't clobber errno if prev_fail is + true. Exposed via Fedora 42's new glibc vs grep's --help being precisely + 4096 bytes. Reported by Jaroslav Škarvada in https://bugs.gnu.org/77800 + 2025-04-17 Paul Eggert memset_explicit-tests: pacify -Wuse-after-free diff --git a/lib/close-stream.c b/lib/close-stream.c index 5dbb19c6ce..576781a251 100644 --- a/lib/close-stream.c +++ b/lib/close-stream.c @@ -61,17 +61,17 @@ close_stream (FILE *stream) /* Return an error indication if there was a previous failure or if fclose failed, with one exception: ignore an fclose failure if there was no previous error, no data remains to be flushed, and - fclose failed with EBADF. That can happen when a program like cp - is invoked like this 'cp a b >&-' (i.e., with standard output - closed) and doesn't generate any output (hence no previous error - and nothing to be flushed). */ + fclose failed with EBADF. In the case of an ignorable fclose + failure, clear errno to avoid misleading diagnostics. That can + happen when a program like cp is invoked like this 'cp a b >&-' + (i.e., with standard output closed) and doesn't generate any output + (hence no previous error and nothing to be flushed). */ - if (prev_fail || (fclose_fail && (some_pending || errno != EBADF))) + if (!prev_fail && fclose_fail && !some_pending && errno == EBADF) { - if (! fclose_fail) - errno = 0; - return EOF; + errno = 0; + return 0; } - return 0; + return prev_fail || (fclose_fail && some_pending) ? EOF : 0; } -- 2.49.0.391.g4bbb303af6