Re: [REGRESSION] git-wrapper to run-commands codepath regression
- From
Jeff King <peff@peff.net>
- Date
- Apr 18, 2011, 21:18 UTC
- Message-ID
- <20110418211849.GB13566@sigill.intra.peff.net>
- In-Reply-To
- <20110418211102.GA13566@sigill.intra.peff.net>
On Mon, Apr 18, 2011 at 05:11:02PM -0400, Jeff King wrote:
Show 13 quoted lines
> The good news is that the bug is trivial. It bisects Jonathan's ebec842 > (run-command: prettify -D_FORTIFY_SOURCE workaround, 2011-03-16), which > introduces: > > - unused = write(child_err, "fatal: ", 7); > - unused = write(child_err, msg, len); > - unused = write(child_err, "\n", 1); > + if (write(child_err, "fatal: ", 7) || > + write(child_err, msg, len) || > + write(child_err, "\n", 1)) > + ; /* yes, gcc -D_FORTIFY_SOURCE, we know there was an error. */ > > Stare at that for a minute and see if you can guess what's wrong. :)
And here's the fix.
-- >8 -- Subject: [PATCH] run-command: fix broken error messages from child
After we fork, we try to exec the child; if exec fails, we write an error message and exit. We ignore the return value of write, since there's nothing we can do about it.
Commit ebec842 turned this into a conditional to make -D_FORTIFY_SOURCE happy with the ignored return value, but botched the change so that we never write more than "fatal:".
Write will return the number of bytes written, so the conditional as written will always appear as an error. Of course we don't actually do anything for the error, but the short-circuit logic means we never execute the subsequent write()s, giving us a truncated error message.
Signed-off-by: Jeff King <peff@peff.net> --- run-command.c | 6 +++--- 1 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/run-command.c b/run-command.c index 8619c76..508a4c6 100644 --- a/run-command.c +++ b/run-command.c @@ -83,9 +83,9 @@ static NORETURN void die_child(const char *err, va_list params) if (len > sizeof(msg)) len = sizeof(msg); - if (write(child_err, "fatal: ", 7) || - write(child_err, msg, len) || - write(child_err, "\n", 1)) + if (write(child_err, "fatal: ", 7) < 0 || + write(child_err, msg, len) < 0 || + write(child_err, "\n", 1) < 0) ; /* yes, gcc -D_FORTIFY_SOURCE, we know there was an error. */ exit(128); }
-- 1.7.5.rc2.3.g728b2