>From 2a06367f7c63d5782ae51af162d68ed2e783e389 Mon Sep 17 00:00:00 2001
From: Jonathan Marler <[email protected]>
Date: Tue, 13 Jul 2021 00:01:03 -0600
Subject: [PATCH] Remove __attribute__((__gnu_inline__)) to allow compiler to
emit functions
The following example works with MSVC but will fail using the mingw headers:
#include <ws2tcpip.h>
int main(int argc, char **argv) {
return (int)&IN6_IS_ADDR_UNSPECIFIED;
}
The reason for this is because MinGW is defining this
`IN6_IS_ADDR_UNSPECIFIED` function with
`extern inline __attribute__((__gnu_inline__))`. A function defined with
these attributes will
NEVER be emitted. This means you cannot take the address of the function
and if the compiler does not inline a call to it, then you'll get a linker
error.
In the Windows SDK in ws2ipdef.h, this function uses the `__inline`
attribute
https://docs.microsoft.com/en-us/cpp/cpp/inline-functions-cpp?view=msvc-160
> This keyword tells the compiler that inline expansion is preferred.
However, the compiler
> can create a separate instance of the function (instantiate) and create
standard calling
> linkages instead of inserting the code inline. Two cases where this
behavior can happen are:
> * Recursive Functions
> * Functions that are referred to through a pointer elsewhere in the
translation unit.
Note that this function is not defined in any .lib or .dll file in the
Windows sdk and/or runtime,
so the only way to be able to take the address of it from the example above
is if the compiler
is able to emit the function, or if it's defined elsewhere.
The problem here appears to be the inclusion of
`__attribute__((__gnu_inline__))` which is what
tells the compiler NEVER to emit the function definition. Removing this
attribute allows the compiler
to emit the function which allows its address to be taken, and prevents
linker errors if the compiler
decides not to inline a call to it.
Note that this applies to multiple functions in the ws2 header files.
Signed-off-by: Jonathan Marler <[email protected]>
---
mingw-w64-headers/crt/_mingw.h.in | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mingw-w64-headers/crt/_mingw.h.in b/mingw-w64-headers/crt/_
mingw.h.in
index b7fb99f42..002079910 100644
--- a/mingw-w64-headers/crt/_mingw.h.in
+++ b/mingw-w64-headers/crt/_mingw.h.in
@@ -87,7 +87,7 @@ limitations in handling dllimport attribute. */
# define __CRT_INLINE __inline
#else
# if ((__MINGW_GNUC_PREREQ(4, 3) || defined(__clang__)) &&
__STDC_VERSION__ >= 199901L)
-# define __CRT_INLINE extern inline __attribute__((__gnu_inline__))
+# define __CRT_INLINE extern inline
# else
# define __CRT_INLINE extern __inline__
# endif
--
2.25.4
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