Re: [cygming] make sure libgcc logic is consistent

[Kai Tietz <ktietz at redhat dot com>]

Hello DJ,

sorry for late reply.  Patch is ok. Please apply.

Thanks,
Kai

----- Original Message -----
> 
> This patch changes the logic in "crtbegin" that looks for libgcc.dll
> such that the test is only done once, guaranteeing consistent results
> between the register and deregister cases.
> 
> Previously, a crash occurred if the application (directly or
> indirectly) caused libgcc.dll to load after main() was called
> (i.e. dlopen'd a DLL which required libgcc).  In that case, the
> register test would return "no libgcc" and register with the local
> copy, yet the deregister test would return "yes libgcc" and try to
> deregister something with libgcc.dll that hadn't been registered.
> 
> Index: cygming-crtbegin.c
> ===================================================================
> --- cygming-crtbegin.c	(revision 212915)
> +++ cygming-crtbegin.c	(working copy)
> @@ -99,12 +99,13 @@ static EH_FRAME_SECTION_CONST char __EH_
>    = { };
>  
>  static struct object obj;
>  
>  /* Handle of libgcc's DLL reference.  */
>  HANDLE hmod_libgcc;
> +static void *  (*deregister_frame_fn) (const void *) == NULL;
>  #endif
>  
>  #if TARGET_USE_JCR_SECTION
>  static void *__JCR_LIST__[]
>    __attribute__ ((used, section(JCR_SECTION_NAME), aligned(4)))
>    = { };
> @@ -130,15 +131,20 @@ __gcc_register_frame (void)
>    if (h)
>      {
>        /* Increasing the load-count of LIBGCC_SONAME DLL.  */
>        hmod_libgcc = LoadLibrary (LIBGCC_SONAME);
>        register_frame_fn = (void (*) (const void *, struct object *))
>  			  GetProcAddress (h, "__register_frame_info");
> +      deregister_frame_fn = (void* (*) (const void *))
> +	                    GetProcAddress (h, "__deregister_frame_info");
> +    }
> +  else
> +    {
> +      register_frame_fn = __register_frame_info;
> +      deregister_frame_fn = __deregister_frame_info;
>      }
> -  else
> -    register_frame_fn = __register_frame_info;
>    if (register_frame_fn)
>       register_frame_fn (__EH_FRAME_BEGIN__, &obj);
>  #endif
>  
>  #if TARGET_USE_JCR_SECTION
>    if (__JCR_LIST__[0])
> @@ -158,19 +164,12 @@ __gcc_register_frame (void)
>  }
>  
>  void
>  __gcc_deregister_frame (void)
>  {
>  #if DWARF2_UNWIND_INFO
> -  void *  (*deregister_frame_fn) (const void *);
> -  HANDLE h = GetModuleHandle (LIBGCC_SONAME);
> -  if (h)
> -    deregister_frame_fn = (void* (*) (const void *))
> -			  GetProcAddress (h, "__deregister_frame_info");
> -  else
> -    deregister_frame_fn = __deregister_frame_info;
>    if (deregister_frame_fn)
>       deregister_frame_fn (__EH_FRAME_BEGIN__);
>    if (hmod_libgcc)
>      FreeLibrary (hmod_libgcc);
>  #endif
>  }
>