On Fri, Dec 9, 2011 at 9:38 AM, Tom de Vries <tom_devr...@mentor.com> wrote: > Jakub, > > This patch fixes the problem reported in > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25973#c4 . > > The test-case listed there is: > ... > struct Block > { > public: > Block(); > ~Block(); > }; > > bool func( bool bar ) > { > Block block; > bool foo = false; > > if( !foo || bar ) > do { return true; } while( 0 ); > else > do { return false; } while( 0 ); > } > ... > > For O0, a spurious warning is generated: > ... > $ gcc -O0 -Wreturn-type block.C -S: > block.C: In function ‘bool func(bool)’: > block.C:17:1: warning: control reaches end of non-void function > [-Wreturn-type] > ... > > Basically the patch tries to handle DO_STMT in block_may_fallthru, but since > it's a cp-tree.def tree, it's done via a language hook. > > Improving block_may_fallthru helps code in gimplify.c:shortcut_cond_expr() to > prevent the superfluous warning: > ... > /* We only emit the jump over the else clause if we have to--if the > then clause may fall through. Otherwise we can wind up with a > useless jump and a useless label at the end of gimplified code, > which will cause us to think that this conditional as a whole > falls through even if it doesn't. If we then inline a function > which ends with such a condition, that can cause us to issue an > inappropriate warning about control reaching the end of a > non-void function. */ > jump_over_else = block_may_fallthru (then_); > ... > > Bootstrapped and reg-tested on x86_64. > > OK for next stage1?
Hm. I would prefer if the gimplifier is fed GENERIC, not GENERIC plus FE specific codes ... (both C and C++ do "genericization" passes, but they actually do not transform all code to GENERIC). Can you check if it's easy enough to lower DO_STMT during cp_genericize? Thanks, Richard. > Thanks, > - Tom >
