Re: [PATCH] merge: fix leak with merge.defaultToUpstream

[Jeff King <peff@peff.net>]

On Tue, Jul 28, 2026 at 03:00:04PM +0200, Toon Claes wrote:

> The leak has been present since 93e535a5b7 (merge: merge with the
> default upstream branch without argument, 2011-03-24). Although the leak
> sanitizer was enabled for tests in fc1ddf42af (t: remove
> TEST_PASSES_SANITIZE_LEAK annotations, 2024-11-21), it went unnoticed
> because no test calls `git merge` without arguments, exercising the
> default-to-upstream path. Add such a test in t7600, which fails under
> the leak sanitizer without this fix.

Wow, I'm surprised we didn't cover this case in the test suite.
Increasing coverage is good.

> @@ -1517,8 +1517,10 @@ int cmd_merge(int argc,
>  		option_commit = 1;
>  
>  	if (!argc) {
> -		if (default_to_upstream)
> +		if (default_to_upstream) {
>  			argc = setup_with_upstream(&argv);
> +			argv_to_free = argv;
> +		}

The fix looks correct to me. This whole argv-juggling is pretty gross
(especially the part below which overwrites argv[0]!). I suspect using a
separate strvec to hold the heads would be cleaner, but it is probably
not worth anybody's time to micro-polish this.

-Peff