[gcc] -freport-bug doesn't work on ICEs

[lazka]

As pointed out in #20864 passing -freport-bug to GCC when it triggers an ICE leads to another error:

Please submit a full bug report, with preprocessed source.
See <https://github.com/msys2/MINGW-packages/issues> for instructions.
gcc: fatal error: cannot execute 'C:/msys64/ucrt64/bin/../lib/gcc/x86_64-w64-mingw32/14.1.0/cc1.exe': open temporary output file: No such file or directory

I don't know what it's supposed to do and if that is worth looking into, since I don't know how to make it do anything without knowing a way to crash gcc.

[ssbssa]

I did a quick grep of the gcc sources for "open temporary output file" and found the likely reason for this.

In gcc/gcc.cc do_report_bug() calls run_attempt(append=1), this append flag gets through pex_run/pex_run_in_environment in libiberty/pex-common.c, which ends in a call of pex_win32_open_write(append=1) in libiberty/pex-win32.c.
The function looks like this:

static int
pex_win32_open_write (struct pex_obj *obj ATTRIBUTE_UNUSED, const char *name,
		      int binary, int append)
{
  /* Note that we can't use O_EXCL here because gcc may have already
     created the temporary file via make_temp_file.  */
  if (append)
    return -1;
  return _open (name,
		(_O_WRONLY | _O_CREAT | _O_TRUNC
		 | (binary ? _O_BINARY : _O_TEXT)),
		_S_IREAD | _S_IWRITE);
}

So it immediately returns -1, which results in this error in pex_run_in_environment():

      out = obj->funcs->open_write (obj, outname,
				    (flags & PEX_BINARY_OUTPUT) != 0,
				    (flags & PEX_STDOUT_APPEND) != 0);
      if (out < 0)
	{
	  *err = errno;
	  errmsg = "open temporary output file";
	  goto error_exit;
	}

No clue how to solve this.