Re: [Mingw-w64-public] no_stack_protector attribute directive is ignored in file stack_chk_guard.c

[LIU Hao]

在 2025-7-13 23:02, Pali Rohár 写道:

I see. But I think it is better to apply at least this "debugging
purposes" attribute than nothing. It is only for older gcc versions.
And with __SSP__ checks it can be targeted just for
-fstack-protector-string CRT builds, which is what the original commit
is aiming.

What about something like this in the stack_chk_guard.c file?

#if !defined(__clang__) && defined(__GNUC__) && __GNUC__ < 11
   #if (defined(__SSP__) || defined(__SSP_STRONG__) || defined(__SSP_ALL__))
     #define __no_stack_protector__ __optimize__("no-stack-protector")
   #else
     #define __no_stack_protector__
   #endif
#endif

It should be an error if SSP is enabled when compiling this file:


diff --git a/mingw-w64-crt/ssp/stack_chk_guard.c 
b/mingw-w64-crt/ssp/stack_chk_guard.c
index be43d8c7e..6a728d712 100644
--- a/mingw-w64-crt/ssp/stack_chk_guard.c
+++ b/mingw-w64-crt/ssp/stack_chk_guard.c
@@ -10,10 +10,18 @@

 void *__stack_chk_guard;

+#if defined __SSP__ || defined __SSP_STRONG__ || defined __SSP_ALL__
 // This function requires `no_stack_protector` because it changes the
 // value of `__stack_chk_guard`, causing stack checks to fail before
 // returning from this function.
-__attribute__((__constructor__, __no_stack_protector__))
+# if (defined __GNUC__ && __GNUC__ >= 11) || (defined __clang__ && 
__clang_major__ >= 7)
+__attribute__((__no_stack_protector__))
+# else
+#  error This file can't be built with stack protector enabled. Remove \
+         -fstack-protector* options from CFLAGS.
+# endif
+#endif
+__attribute__((__constructor__))
 static void __cdecl init(void)
 {
   unsigned int ui;



--
Best regards,
LIU Hao

I'd rather that we don't abuse the `optimize` attribute. Clang also doesn't support it, so there's no workaround for Clang 7-.

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