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run-command: handle short writes and EINTR in die_child

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If start_command fails after forking and before exec finishes, there
is not much use in noticing an I/O error on top of that.
finish_command will notice that the child exited with nonzero status
anyway.  So as noted in v1.7.0.3~20^2 (run-command.c: fix build
warnings on Ubuntu, 2010-01-30) and v1.7.5-rc0~29^2 (2011-03-16), it
is safe to ignore errors from write in this codepath.

Even so, the result from write contains useful information: it tells
us if the write was cancelled by a signal (EINTR) or was only
partially completed (e.g., when writing to an almost-full pipe).
Let's use write_in_full to loop until the desired number of bytes have
been written (still ignoring errors if that fails).

As a happy side effect, the assignment to a dummy variable to appease
gcc -D_FORTIFY_SOURCE is no longer needed.  xwrite and write_in_full
check the return value from write(2).

Noticed with gcc -Wunused-but-set-variable.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Jonathan Nieder 2011-04-20 05:40:05 -05:00 committed by Junio C Hamano
parent c0f19bf3b9
commit a111eb7808
1 changed files with 9 additions and 6 deletions
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15
run-command.c
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@ -67,21 +67,24 @@ static int child_notifier = -1;
static void notify_parent(void)
{
ssize_t unused;
unused = write(child_notifier, "", 1);
/*
* execvp failed. If possible, we'd like to let start_command
* know, so failures like ENOENT can be handled right away; but
* otherwise, finish_command will still report the error.
*/
xwrite(child_notifier, "", 1);
}
static NORETURN void die_child(const char *err, va_list params)
{
char msg[4096];
ssize_t unused;
int len = vsnprintf(msg, sizeof(msg), err, params);
if (len > sizeof(msg))
len = sizeof(msg);
unused = write(child_err, "fatal: ", 7);
unused = write(child_err, msg, len);
unused = write(child_err, "\n", 1);
write_in_full(child_err, "fatal: ", 7);
write_in_full(child_err, msg, len);
write_in_full(child_err, "\n", 1);
exit(128);
}
#endif