[Bug c/77750] [7 Regression] gcc build not working with -O0

["louis.krupp at zoho dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77750

--- Comment #8 from louis.krupp at zoho dot com ---
The patch is no longer necessary, because it looks like the problem with
combine.c was fixed on 1 November:

===
r241744 | foreese | 2016-11-01 09:29:51 -0600 (Tue, 01 Nov 2016) | 5 lines

Mark fallthrough cases with gcc_fallthrough.

        * gcc/combine.c (simplify_compare_const): Add gcc_fallthrough.
===

and my guess is that the problem with the fall-through comment format in
fold-const.c went away back in October when you fixed lex.c:

===
r241013 | jakub | 2016-10-11 17:19:06 -0600 (Tue, 11 Oct 2016) | 31 lines

gcc/
        * common.opt (Wimplicit-fallthrough) Turn into alias to
        -Wimplicit-fallthrough=3.  Remove EnabledBy.
        (Wimplicit-fallthrough=): New option.
        * gimplify.c (warn_implicit_fallthrough_r): Use
        OPT_Wimplicit_fallthrough_ instead of OPT_Wimplicit_fallthrough.
        * doc/invoke.texi (-Wimplicit-fallthrough): Document as alias
        to -Wimplicit-fallthrough=3.
        (-Wimplicit-fallthrough=): Document.
gcc/c-family/
        * c.opt (Wextra): Add as C/C++/ObjC/ObjC++ option.
        (Wimplicit-fallthrough=): Enable for these languages by -Wextra.
        * c-opts.c (sanitize_cpp_opts): Initialize
        cpp_opts->cpp_warn_implicit_fallthrough.
gcc/testsuite/
        * c-c++-common/Wimplicit-fallthrough-25.c: New test.
        * c-c++-common/Wimplicit-fallthrough-26.c: New test.
        * c-c++-common/Wimplicit-fallthrough-27.c: New test.
        * c-c++-common/Wimplicit-fallthrough-28.c: New test.
        * c-c++-common/Wimplicit-fallthrough-29.c: New test.
        * c-c++-common/Wimplicit-fallthrough-30.c: New test.
        * c-c++-common/Wimplicit-fallthrough-31.c: New test.
        * c-c++-common/Wimplicit-fallthrough-32.c: New test.
        * c-c++-common/Wimplicit-fallthrough-33.c: New test.
libcpp/
        * include/cpplib.h (struct cpp_options): Add
        cpp_warn_implicit_fallthrough.
        * init.c (cpp_create_reader): Initialize it to 0.
        * lex.c (fallthrough_comment_p): Handle different
        cpp_warn_implicit_fallthrough levels.  Whitespace fixes.
===

Thank you for doing that.

Would you like to close pr77750, since you fixed part of it, or shall I?

Louis




 ---- On Wed, 09 Nov 2016 06:44:59 -0800 jakub at gcc dot gnu.org
<gcc-bugzilla@gcc.gnu.org> wrote ---- 
 > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77750 
 >  
 > Jakub Jelinek <jakub at gcc dot gnu.org> changed: 
 >  
 >            What    |Removed                     |Added 
 > ---------------------------------------------------------------------------- 
 >                  CC|                            |jakub at gcc dot gnu.org 
 >  
 > --- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> --- 
 > I don't see why the #c6 patch should be necessary, nor can reproduce this. 
 > Are you using some older trunk version as bootstrap compiler, or something 
 > similar? 
 > E.g. the first case is: 
 >     case LT: 
 >       /* < C is equivalent to <= (C - 1) */ 
 >       if (const_op > 0) 
 >         { 
 >           const_op -= 1; 
 >           code = LE; 
 >           /* ... fall through to LE case below.  */ 
 >           gcc_fallthrough (); 
 >         } 
 >       else 
 >         break; 
 >  
 >     case LE: 
 > and there really is no need for any fallthrough comment, gcc_fallthrough (); 
 > already represents that and works even at -O0. 
 >  
 > --  
 > You are receiving this mail because: 
 > You reported the bug.