git/common-main.c
Ævar Arnfjörð Bjarmason 368b584315 common-main.c: call exit(), don't return
Change the main() function to call "exit()" instead of ending with a
"return" statement. The "exit()" function is our own wrapper that
calls trace2_cmd_exit_fl() for us, from git-compat-util.h:

	#define exit(code) exit(trace2_cmd_exit_fl(__FILE__, __LINE__, (code)))

That "exit()" wrapper has been in use ever since ee4512ed48 (trace2:
create new combined trace facility, 2019-02-22).

This changes nothing about how we "exit()", as we'd invoke
"trace2_cmd_exit_fl()" in both cases due to the wrapper, this change
makes it easier to reason about this code, as we're now always
obviously relying on our "exit()" wrapper.

There is already code immediately downstream of our "main()" which has
a hard reliance on that, e.g. the various "exit()" calls downstream of
"cmd_main()" in "git.c".

We even had a comment in "t/helper/test-trace2.c" that seemed to be
confused about how the "exit()" wrapper interacted with uses of
"return", even though it was introduced in the same trace2 series in
a15860dca3 (trace2: t/helper/test-trace2, t0210.sh, t0211.sh,
t0212.sh, 2019-02-22), after the aforementioned ee4512ed48. Perhaps
it pre-dated the "exit()" wrapper?

This change makes the "trace2_cmd_exit()" macro orphaned, we now
always use "trace2_cmd_exit_fl()" directly, but let's keep that
simpler example in place. Even if we're unlikely to get another
"main()" other than the one in our "common-main.c", there's some value
in having the API documentation and example discuss a simpler version
that doesn't require an "exit()" wrapper macro.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-12-07 12:29:57 -08:00

61 lines
1.5 KiB
C

#include "cache.h"
#include "exec-cmd.h"
#include "attr.h"
/*
* Many parts of Git have subprograms communicate via pipe, expect the
* upstream of a pipe to die with SIGPIPE when the downstream of a
* pipe does not need to read all that is written. Some third-party
* programs that ignore or block SIGPIPE for their own reason forget
* to restore SIGPIPE handling to the default before spawning Git and
* break this carefully orchestrated machinery.
*
* Restore the way SIGPIPE is handled to default, which is what we
* expect.
*/
static void restore_sigpipe_to_default(void)
{
sigset_t unblock;
sigemptyset(&unblock);
sigaddset(&unblock, SIGPIPE);
sigprocmask(SIG_UNBLOCK, &unblock, NULL);
signal(SIGPIPE, SIG_DFL);
}
int main(int argc, const char **argv)
{
int result;
trace2_initialize_clock();
/*
* Always open file descriptors 0/1/2 to avoid clobbering files
* in die(). It also avoids messing up when the pipes are dup'ed
* onto stdin/stdout/stderr in the child processes we spawn.
*/
sanitize_stdfds();
restore_sigpipe_to_default();
git_resolve_executable_dir(argv[0]);
git_setup_gettext();
initialize_the_repository();
attr_start();
trace2_initialize();
trace2_cmd_start(argv);
trace2_collect_process_info(TRACE2_PROCESS_INFO_STARTUP);
result = cmd_main(argc, argv);
/*
* We define exit() to call trace2_cmd_exit_fl() in
* git-compat-util.h. Whether we reach this or exit()
* elsewhere we'll always run our trace2 exit handler.
*/
exit(result);
}