gcc-12: Re-enable split-stack support for GNU/Hurd.

  Hello,

In line of porting the latest build of libgo/go with gcc-12 to GNU/Hurd, support
of split-stack was found to be removed.
 
After patching the files in libgo the build of gotools fails:
go1: error: '-fsplit-stack' currently only supported on GNU/Linux
go1: error: '-fsplit-stack' is not supported by this compiler configuration

The attached patch defines OPTION_GLIBC_P(opts) and OPTION_GLIBC that was lost
in config/gnu.h, needed to enable split-stack support for GNU/Hurd. 

This problem happened with the latest commit as discussed in the mail thread
starting with https://gcc.gnu.org/pipermail/gcc-patches/2022-January/588973.html
.

The file first doing this check is: (first error: ..)
src/gcc/common/config/i386/i386-common.cc
in function:
static bool ix86_supports_split_stack (bool report,
            struct gcc_options *opts ATTRIBUTE_UNUSED)

and secondly in:src/gcc/opts.cc: (second error: ...)
in function:
void
finish_options (struct gcc_options *opts, struct gcc_options *opts_set,
                location_t loc)

The checking logic is in function ix86_supports_split_stack():
#if defined(TARGET_THREAD_SPLIT_STACK_OFFSET) && defined(OPTION_GLIBC_P)
  if (!OPTION_GLIBC_P (opts))
#endif
    {
      if (report)
        error ("%<-fsplit-stack%> currently only supported on GNU/Linux");
      return false;
    }

  bool ret = true;

In case of GNU/Hurd TARGET_THREAD_SPLIT_STACK_OFFSET is defined as well as
OPTION_GLIBC_P but OPTION_GLIBC_P(opts) is needed to. The attached patch to
src/gcc/config/gnu.h creates that definition. For GNU/Hurd, gnu.h is included in
the configure stage:
Configuring stage 1 in ./gcc
...
Using the following target machine macro files:
...
        ../../src/gcc/config/gnu.h

For a longer history about this bug see:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104290

Additionally, I would propose the text in gcc/common/config/i386/i386-common.cc
to change from:
error ("%<-fsplit-stack%> currently only supported on GNU/Linux");
to:
error ("%<-fsplit-stack%> currently only supported on GLIBC-based systems");

Thanks!
  

ping

On Wed, 2022-02-23 at 11:13 +0100, Svante Signell wrote:
> Hello,
> 
> In line of porting the latest build of libgo/go with gcc-12 to GNU/Hurd,
> support
> of split-stack was found to be removed.
>  
> After patching the files in libgo the build of gotools fails:
> go1: error: '-fsplit-stack' currently only supported on GNU/Linux
> go1: error: '-fsplit-stack' is not supported by this compiler configuration
> 
> The attached patch defines OPTION_GLIBC_P(opts) and OPTION_GLIBC that was lost
> in config/gnu.h, needed to enable split-stack support for GNU/Hurd. 
> 
> This problem happened with the latest commit as discussed in the mail thread
> starting with 
> https://gcc.gnu.org/pipermail/gcc-patches/2022-January/588973.html
> .
> 
> The file first doing this check is: (first error: ..)
> src/gcc/common/config/i386/i386-common.cc
> in function:
> static bool ix86_supports_split_stack (bool report,
>             struct gcc_options *opts ATTRIBUTE_UNUSED)
> 
> and secondly in:src/gcc/opts.cc: (second error: ...)
> in function:
> void
> finish_options (struct gcc_options *opts, struct gcc_options *opts_set,
>                 location_t loc)
> 
> The checking logic is in function ix86_supports_split_stack():
> #if defined(TARGET_THREAD_SPLIT_STACK_OFFSET) && defined(OPTION_GLIBC_P)
>   if (!OPTION_GLIBC_P (opts))
> #endif
>     {
>       if (report)
>         error ("%<-fsplit-stack%> currently only supported on GNU/Linux");
>       return false;
>     }
> 
>   bool ret = true;
> 
> In case of GNU/Hurd TARGET_THREAD_SPLIT_STACK_OFFSET is defined as well as
> OPTION_GLIBC_P but OPTION_GLIBC_P(opts) is needed to. The attached patch to
> src/gcc/config/gnu.h creates that definition. For GNU/Hurd, gnu.h is included
> in
> the configure stage:
> Configuring stage 1 in ./gcc
> ...
> Using the following target machine macro files:
> ...
>         ../../src/gcc/config/gnu.h
> 
> For a longer history about this bug see:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104290
> 
> Additionally, I would propose the text in gcc/common/config/i386/i386-
> common.cc
> to change from:
> error ("%<-fsplit-stack%> currently only supported on GNU/Linux");
> to:
> error ("%<-fsplit-stack%> currently only supported on GLIBC-based systems");
> 
> Thanks!