On Mon, Jun 10, 2024 at 01:05:00PM -0700, Junio C Hamano wrote: > Junio C Hamano <gitster@xxxxxxxxx> writes: > > > These "workarounds" are to mark variables that are used after > > initialized, but some compilers with lower optimization levels > > cannot see and report "used uninitialized". > > > > This set targets "gcc-12 -Og". For the reason why this is a wrong > > thing to do for longer-term code health, see > > > > https://lore.kernel.org/git/xmqqed946auc.fsf@gitster.g/ > > > > Signed-off-by: Junio C Hamano <gitster@xxxxxxxxx> > > --- > > > > * Even though I said I won't do the actual patch, since I had to > > gauge the extent of damage, I ended up doing so anyways. > > > > As I explained already, the size of this patch, i.e. number of > > places that need the workaround, does not really matter. What > > is horrible is how each of these workaround will hide real bugs > > we may introduce in the future from the compilers. > > > > builtin/branch.c | 2 +- > > builtin/fast-import.c | 4 ++-- > > builtin/repack.c | 2 +- > > fetch-pack.c | 2 +- > > http-backend.c | 2 +- > > http.c | 2 +- > > pack-mtimes.c | 2 +- > > pack-revindex.c | 2 +- > > refs/packed-backend.c | 2 +- > > reftable/stack.c | 2 +- > > remote-curl.c | 4 ++-- > > t/helper/test-ref-store.c | 2 +- > > trailer.c | 4 ++-- > > 13 files changed, 16 insertions(+), 16 deletions(-) > > And depending on the version of compilers, apparently even this is > not enough. I do not offhand know what GitHub CI is running for > linux-gcc-default (ubuntu-latest), but this gets flagged for using > (try to guess which one without looking at the answer below) ... > > static int parse_count(const char *arg) > { > int count; > > if (strtol_i(arg, 10, &count) < 0) > die("'%s': not an integer", arg); > return count; > } > > ... count uninitilaized, since the compiler does not realize that > strtol_i() always touches "count" unless the function returns > negative, and die() never returns. Exactly the same pattern > continues. > > So, unless we disable -Werror, let's not continue this experiment > with -Og or -Os as the damage seems to be far greater than the > benefit (which I haven't seen any, but that is largely due to > timezone differences---I asked "what's the real bug you found with > this" a few hours ago that is past EOB in Europe). The real bug that "-Og" would have been able to detect was reported by Peff via [1]. In this case it wasn't "-Og" that detected it, but Coverity did. But it would have been detected if we had a job that compiled with "-Og". But now that I see the full picture of this with different compiler options I have to agree that this is not really worth it. Especially not given that Coverity is able to detect such cases, even though that only happens retroactively after a topic has landed. Let's drop this experiment. Patrick [1]: 20240605100728.GA3440281@xxxxxxxxxxxxxxxxxxxxxxx
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