Re: [Mingw-w64-public] Bug in setjmp.h on win64 + SEH

[Tristan G. <gi...@ad...>]

On Jun 8, 2012, at 1:55 PM, JonY wrote:

> On 6/8/2012 18:27, Tristan Gingold wrote:
>> Hi,
>> 
>> I am currently working on porting our toolset to gcc 4.7 compiled to fully support SEH, and I have compiled gdb.  This gdb crashes frequently, and I traced that to the use of setjmp/longjmp.
>> 
>> When compiled with SEH enabled, mingw64 makes longjmp use RtlUnwinEx, and to achieve that it calls _setjmp with a non-null establisher frame.
>> Currently, it uses mingw_getsp() for that.  Unfortunately, this is wrong.  This establisher frame is the frame pointer defined in the Frame Pointer field of the UNWIND_INFO structure (and rsp if this field is nul).  In case of mismatch, longjmp is not able to find the target frame and aborts the program.
>> 
>> The easiest fix is to use __builtin_frame_address (0), which forces the use of a frame pointer and returns its value.  This is not optimal (would be nice not to force the user of a frame pointer), but I am not sure gcc could do better.
>> 
>> Here is the patch, with a little bit of reformatting (because I found the nested directives hard to read).
>> 
>> There are also some bugs in the generation of SEH directive in gcc 4.7, and I plan to send patch to the gcc ML for that.
>> 
>> Tristan.
> 
> Hi,
> 
> Can you please use unified diff?

Sure.

Note that I prefer to consider this as an request for comment.  I haven't seen yet any precise definition of what is an establisher frame, so this might still be wrong.

Tristan.


--- setjmp.h~	2012-05-07 17:11:59.000000000 +0200
+++ setjmp.h	2012-06-08 11:37:34.000000000 +0200
@@ -148,34 +148,32 @@
 #define _JMP_BUF_DEFINED
 #endif
 
-  void * __cdecl __attribute__ ((__nothrow__)) mingw_getsp(void);
-
 #ifndef USE_NO_MINGW_SETJMP_TWO_ARGS
-#ifndef _INC_SETJMPEX
-#ifdef _WIN64
-#define setjmp(BUF) _setjmp((BUF), mingw_getsp())
-#else
-#define setjmp(BUF) _setjmp3((BUF), NULL)
-#endif
+#  ifndef _INC_SETJMPEX
+#    ifdef _WIN64
+#      define setjmp(BUF) _setjmp((BUF), __builtin_frame_address (0))
+#    else
+#      define setjmp(BUF) _setjmp3((BUF), NULL)
+#    endif
   int __cdecl __attribute__ ((__nothrow__,__returns_twice__)) _setjmp(jmp_buf _Buf, void *_Ctx);
   int __cdecl __attribute__ ((__nothrow__,__returns_twice__)) _setjmp3(jmp_buf _Buf, void *_Ctx);
-#else
-#undef setjmp
-#ifdef _WIN64
-#define setjmp(BUF) _setjmpex((BUF), mingw_getsp())
-#define setjmpex(BUF) _setjmpex((BUF), mingw_getsp())
-#else
-#define setjmp(BUF) _setjmpex((BUF), NULL)
-#define setjmpex(BUF) _setjmpex((BUF), NULL)
-#endif
+#  else
+#    undef setjmp
+#    ifdef _WIN64
+#      define setjmp(BUF) _setjmpex((BUF), __builtin_frame_address (0))
+#      define setjmpex(BUF) _setjmpex((BUF), __builtin_frame_address (0))
+#    else
+#      define setjmp(BUF) _setjmpex((BUF), NULL)
+#      define setjmpex(BUF) _setjmpex((BUF), NULL)
+#    endif
   int __cdecl __attribute__ ((__nothrow__,__returns_twice__)) _setjmpex(jmp_buf _Buf,void *_Ctx);
-#endif
+#  endif
 
 #else
 
-#ifndef _INC_SETJMPEX
-#define setjmp _setjmp
-#endif
+#  ifndef _INC_SETJMPEX
+#    define setjmp _setjmp
+#  endif
 
   int __cdecl __attribute__ ((__nothrow__,__returns_twice__)) setjmp(jmp_buf _Buf);
 #endif