[PATCH v2 6/6] max_tree_depth: lower it for clangarm64 on Windows

From: Johannes Schindelin via GitGitGadget <gitgitgadget@gmail.com>
Date: Apr 23, 2025, 08:01 UTC
Message-ID: <e0e78bd5131a9efa64697cd7c0bd30965d13b41c.1745395308.git.gitgitgadget@gmail.com>
In-Reply-To: <pull.1904.v2.git.1745395308.gitgitgadget@gmail.com>

From: Johannes Schindelin <johannes.schindelin@gmx.de>

Just as in b64d78ad02ca (max_tree_depth: lower it for MSVC to avoid stack overflows, 2023-11-01), I encountered the same problem with the clang builds on Windows/ARM64.

The symptom is an exit code 127 when t6700 tries to verify that `git archive big` fails.

This exit code is reserved on Unix/Linux to mean "command not found". Unfortunately in this case, it is the fall-back chosen by Cygwin's `pinfo::status_exit()` method when encountering the NSTATUS `STATUS_STACK_OVERFLOW`, see https://github.com/cygwin/cygwin/blob/cygwin-3.6.1/winsup/cygwin/pinfo.cc#L171

I verified manually that the stack overflow always happens somewhere around tree depth 1403, therefore 1280 should be a safe bound in these instances.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 environment.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/environment.c b/environment.c
index 9e4c7781be0..d948bb3c705 100644
--- a/environment.c
+++ b/environment.c
@@ -82,6 +82,16 @@ int max_allowed_tree_depth =
 	 * the stack overflow can occur.
 	 */
 	512;
+#elif defined(GIT_WINDOWS_NATIVE) && defined(__clang__) && defined(__aarch64__)
+	/*
+	 * 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

-- 
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