run-command: handle short writes and EINTR in die_child

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>

diff --git a/run-command.c b/run-command.c
index f91e446c86be8e27f98554567143d7ce6f934bd1..70e8a249d0fe07b6a32b4da4ac8224d1c2f06b1b 100644 (file)
--- a/run-command.c
+++ b/run-command.c
@@ -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