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Revision d88785e424aaf18aa3ca291c2299c599c000c6cb authored by Jeff King on 11 May 2016, 13:44:04 UTC, committed by Junio C Hamano on 11 May 2016, 21:03:14 UTC 
test-lib: set BASH_XTRACEFD automatically
 
Passing "-x" to a test script enables the shell's "set -x"
tracing, which can help with tracking down the command that
is causing a failure. Unfortunately, it can also _cause_
failures in some tests that redirect the stderr of a shell
function.  Inside the function the shell continues to
respect "set -x", and the trace output is collected along
with whatever stderr is generated normally by the function.

You can see an example of this by running:

  ./t0040-parse-options.sh -x -i

which will fail immediately in the first test, as it
expects:

  test_must_fail some-cmd 2>output.err

to leave output.err empty (but with "-x" it has our trace
output).

Unfortunately there isn't a portable or scalable solution to
this. We could teach test_must_fail to disable "set -x", but
that doesn't help any of the other functions or subshells.

However, we can work around it by pointing the "set -x"
output to our descriptor 4, which always points to the
original stderr of the test script. Unfortunately this only
works for bash, but it's better than nothing (and other
shells will just ignore the BASH_XTRACEFD variable).

The patch itself is a simple one-liner, but note the caveats
in the accompanying comments.

Automatic tests for our "-x" option may be a bit too meta
(and a pain, because they are bash-specific), but I did
confirm that it works correctly both with regular "-x" and
with "--verbose-only=1". This works because the latter flips
"set -x" off and on for particular tests (if it didn't, we
would get tracing for all tests, as going to descriptor 4
effectively circumvents the verbose flag).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
1 parent 7654286
Raw File
write_or_die.c 
#include "cache.h"

static void check_pipe(int err)
{
	if (err == EPIPE) {
		signal(SIGPIPE, SIG_DFL);
		raise(SIGPIPE);
		/* Should never happen, but just in case... */
		exit(141);
	}
}

/*
 * Some cases use stdio, but want to flush after the write
 * to get error handling (and to get better interactive
 * behaviour - not buffering excessively).
 *
 * Of course, if the flush happened within the write itself,
 * we've already lost the error code, and cannot report it any
 * more. So we just ignore that case instead (and hope we get
 * the right error code on the flush).
 *
 * If the file handle is stdout, and stdout is a file, then skip the
 * flush entirely since it's not needed.
 */
void maybe_flush_or_die(FILE *f, const char *desc)
{
	static int skip_stdout_flush = -1;
	struct stat st;
	char *cp;

	if (f == stdout) {
		if (skip_stdout_flush < 0) {
			cp = getenv("GIT_FLUSH");
			if (cp)
				skip_stdout_flush = (atoi(cp) == 0);
			else if ((fstat(fileno(stdout), &st) == 0) &&
				 S_ISREG(st.st_mode))
				skip_stdout_flush = 1;
			else
				skip_stdout_flush = 0;
		}
		if (skip_stdout_flush && !ferror(f))
			return;
	}
	if (fflush(f)) {
		check_pipe(errno);
		die_errno("write failure on '%s'", desc);
	}
}

void fprintf_or_die(FILE *f, const char *fmt, ...)
{
	va_list ap;
	int ret;

	va_start(ap, fmt);
	ret = vfprintf(f, fmt, ap);
	va_end(ap);

	if (ret < 0) {
		check_pipe(errno);
		die_errno("write error");
	}
}

void fsync_or_die(int fd, const char *msg)
{
	if (fsync(fd) < 0) {
		die_errno("fsync error on '%s'", msg);
	}
}

void write_or_die(int fd, const void *buf, size_t count)
{
	if (write_in_full(fd, buf, count) < 0) {
		check_pipe(errno);
		die_errno("write error");
	}
}

int write_or_whine_pipe(int fd, const void *buf, size_t count, const char *msg)
{
	if (write_in_full(fd, buf, count) < 0) {
		check_pipe(errno);
		fprintf(stderr, "%s: write error (%s)\n",
			msg, strerror(errno));
		return 0;
	}

	return 1;
}

int write_or_whine(int fd, const void *buf, size_t count, const char *msg)
{
	if (write_in_full(fd, buf, count) < 0) {
		fprintf(stderr, "%s: write error (%s)\n",
			msg, strerror(errno));
		return 0;
	}

	return 1;
}
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