From 2253303f1165d994a39a18254c39961f54ba6d5d Mon Sep 17 00:00:00 2001
From: Adam Murray <ad@canva.com>
Date: Thu, 7 Nov 2024 09:46:14 +1000
Subject: [PATCH] trace2: prevent segfault on config collection where no value
 specified

When TRACE2 analytics is enabled, a git config option that has no value
causes a segfault.

Steps to Reproduce
GIT_TRACE2=true GIT_TRACE2_CONFIG_PARAMS=status.*
git -c status.relativePaths version
Expected Result
git version 2.46.0
Actual Result
zsh: segmentation fault GIT_TRACE2=true

This adds a null check to prevent the segfault and instead return
the "empty config value" error.
---
 t/t0210-trace2-normal.sh | 8 ++++++++
 trace2.c                 | 2 +-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/t/t0210-trace2-normal.sh b/t/t0210-trace2-normal.sh
index b9adc94aab4165..4047ab562a455e 100755
--- a/t/t0210-trace2-normal.sh
+++ b/t/t0210-trace2-normal.sh
@@ -244,6 +244,14 @@ test_expect_success 'bug messages followed by BUG() are written to trace2' '
 	test_cmp expect actual
 '
 
+test_expect_success 'empty configuration values are handled' '
+  test_when_finished "rm trace2.normal actual expect" &&
+  echo >expect &&
+  GIT_TRACE2="$(pwd)/trace2.normal"  GIT_TRACE2_CONFIG_PARAMS=foo.empty \
+	  git -c foo.empty config foo.empty >actual &&
+	test_cmp expect actual
+'
+
 sane_unset GIT_TRACE2_BRIEF
 
 # Now test without environment variables and get all Trace2 settings
diff --git a/trace2.c b/trace2.c
index f894532d05331c..5df43478b8fb22 100644
--- a/trace2.c
+++ b/trace2.c
@@ -759,7 +759,7 @@ void trace2_def_param_fl(const char *file, int line, const char *param,
 	int j;
 	const char *redacted;
 
-	if (!trace2_enabled)
+	if (!trace2_enabled || !value)
 		return;
 
 	redacted = redact_arg(value);