Re: [PATCH 6/6] max_tree_depth: lower it for clangarm64 on Windows

From: Patrick Steinhardt <ps@pks.im>
Date: Apr 22, 2025, 07:43 UTC
Message-ID: <aAdImbydzMUkCFqB@pks.im>
In-Reply-To: <6ebc3ef57fd0455fc70c4a8531c7ed094d9cdaff.1745239150.git.gitgitgadget@gmail.com>

On Mon, Apr 21, 2025 at 12:39:10PM +0000, Johannes Schindelin via GitGitGadget wrote:

Show 10 quoted lines

> diff --git a/environment.c b/environment.c
> index 9e4c7781be0..cc853950bb2 100644
> --- a/environment.c
> +++ b/environment.c
> @@ -82,9 +82,21 @@ int max_allowed_tree_depth =
>  	 * the stack overflow can occur.
>  	 */
>  	512;
> +#else
> +#if defined(GIT_WINDOWS_NATIVE) && defined(__clang__) && defined(__aarch64__)

Tiny nit, only because it puzzled me for a second: this should probably be `#elif`.

Show 13 quoted lines

> +	/*
> +	 * Similar to Visual C, it seems that on Windows/ARM64 the clang-based
> +	 * builds have a smaller stack space available. When running out of
> +	 * that stack space, a `STATUS_STACK_OVERFLOW` is produced. When the
> +	 * Git command was run from an MSYS2 Bash, this unfortunately results
> +	 * in an exit code 127. Let's prevent that by lowering the maximal
> +	 * tree depth; This value seems to be low enough.
> +	 */
> +	1280;
>  #else
>  	2048;
>  #endif
> +#endif

Hm. This whole construct feels rather awful, if you ask me. Instead of papering over the issue it would be nice if we eventually fixed the root cause, which is that we use recursion on a data structure that has an unbounded depth in theory.

Anyway, that is clearly outside of the scope of this patch series, so the bandaid is good enough for now.

Patrick