From 4d31d28e33109fde145a10b6063ae6fe6757bfec Mon Sep 17 00:00:00 2001
From: "Tobias S. Josefowitz" <tobij@tobij.de>
Date: Tue, 16 Mar 2021 21:51:16 +0100
Subject: [PATCH] Build [Configure]: Prevent inling of find_stack_direction()
Clang 11 has either learned to inline find_stack_direction(), or it may
have inlined find_stack_direction() before but changed allocation order
for our "objects with automatic storage duration" that we use to check
the stack direction.
Calling find_stack_direction() through a volatile function pointer
should reliably prevent it from getting inlined and thus flush out the
real stack direction.
Thanks to Cezary Cerekwicki <ccerekwicki@opera.com> for the report.
---
src/configure.in | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/src/configure.in b/src/configure.in
index fde19017ea..5a2e1a1a4f 100644
--- a/src/configure.in
+++ b/src/configure.in
@@ -4689,9 +4689,10 @@ AC_CACHE_VAL(pike_cv_hardware_stack_direction,
[
AC_TRY_RUN([
#include <stdio.h>
+static int (* volatile find_stack_direction_funptr)(void *foo, int cnt);
static int find_stack_direction(void *foo, int cnt)
{
- if (cnt) return 1*find_stack_direction(foo, cnt>>1);
+ if (cnt) return 1*find_stack_direction_funptr(foo, cnt>>1);
if (((void *)&foo) > foo) {
return 1;
} else {
@@ -4699,7 +4700,10 @@ static int find_stack_direction(void *foo, int cnt)
}
}
-int main() { void *bar; exit( find_stack_direction(&bar, 0x10) > 0); }
+int main() {
+ find_stack_direction_funptr = &find_stack_direction;
+ void *bar; exit( find_stack_direction_funptr(&bar, 0x10) > 0);
+}
], [ pike_cv_hardware_stack_direction=down
], [ pike_cv_hardware_stack_direction=up
], [
--
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