https://git.ruby-lang.org/ruby.git/commit/?id=40ceceb1a5

From 40ceceb1a5b63029a4d1434d2d20dfa09cdb295f Mon Sep 17 00:00:00 2001
From: Nobuyoshi Nakada <nobu@r...>
Date: Tue, 4 Oct 2022 10:54:28 +0900
Subject: [Bug #19028] Suppress GCC 12 `-Wuse-after-free` false warning

GCC 12 introduced a new warning flag `-Wuse-after-free`, however it
has a false positive at `realloc` when optimization is disabled, since
the memory requested for reallocation is guaranteed to not be touched.
This workaround is very unclear why the false warning is suppressed by
a statement-expression GCC extension.
---
 gc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gc.c b/gc.c
index 0ba28ba67b..c1b06a76e7 100644
--- a/gc.c
+++ b/gc.c
@@ -12236,7 +12236,7 @@ objspace_xrealloc(rb_objspace_t *objspace, void *ptr, size_t new_size, size_t ol https://github.com/ruby/ruby/blob/trunk/gc.c#L12236
 #endif
 
     old_size = objspace_malloc_size(objspace, ptr, old_size);
-    TRY_WITH_GC(new_size, mem = realloc(ptr, new_size));
+    TRY_WITH_GC(new_size, mem = RB_GNUC_EXTENSION_BLOCK(realloc(ptr, new_size)));
     new_size = objspace_malloc_size(objspace, mem, new_size);
 
 #if CALC_EXACT_MALLOC_SIZE
-- 
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