On Sun, Oct 12, 2014 at 2:03 PM, Dan Douglas <orm...@gmail.com> wrote: > On Sun, Oct 12, 2014 at 11:22 AM, Anthony G. Basile <bluen...@gentoo.org> > wrote: >> Hi everyone, >> >> I'd like to add the patch below to toolchain-funcs.eclass. I need it for >> bug #499996 and it helps to address a category of bugs which gcc-4.8 >> uncovers. 4.8 and above introduces -fstack-check. This is code emitted by >> gcc to make sure you don't go past the beyond the boundary of the stack in a >> multithreaded environment. It requires one register on at least i686 and >> amd64, but I'm not sure about the others. In asm heavy code, such as vlc >> and ffmpeg, we hit the limit of useable registers pretty quickly and go over >> the top with either -fstack-check or pie. We have tests to check for pie in >> toolchain-funcs, but not for stack-check. The following adds that check. I >> tested it already. I'll commit in a few days if there are no objections. >> >> --- toolchain-funcs.eclass.orig 2014-10-12 11:23:41.585182742 -0400 >> +++ toolchain-funcs.eclass 2014-10-12 11:31:57.170205300 -0400 >> @@ -610,6 +610,12 @@ >> directive=$(gcc-specs-directive cc1) >> return $([[ "${directive/\{!fstrict-overflow:}" != "${directive}" ]]) >> } >> +# Returns true if gcc builds with fstack-check >> +gcc-specs-stack-check() { >> + local directive >> + directive=$(gcc-specs-directive cc1) >> + return $([[ "${directive/\{!fno-stack-check:}" != "${directive}" ]]) >> +} >> >> >> # @FUNCTION: gen_usr_ldscript > > Am I missing something here? I don't see how any of the tests used in > gcc-specs-* functions could possibly produce an output. The fact that this > coincidentally works in Bash shouldn't be relied upon. >
I think he just copy/pasted the style of the other gcc-specs functions. I think they could all be improved by removing that weird/unnecessary subshell, which always evaluates to an empty string. When passed no arguments, the return statement just defaults to the value of $?, which in this case is the exit status of the subshell. So, instead of this: return $([[ "${directive/\{!fno-stack-check:}" != "${directive}" ]]) Just do this: [[ "${directive/\{!fno-stack-check:}" != "${directive}" ]] Which should be equivalent.