Yes Sir, I will go through the dump from uninit pass with required optimizations.I will try the tree-ssa-uninit.cc on gdb. Thanks and Regards, Krishna Narayanan. On Wed, Feb 9, 2022 at 3:20 AM Martin Sebor <msebor@xxxxxxxxx> wrote: > On 2/8/22 10:37, Jonathan Wakely via Gcc-help wrote: > > On Tue, 8 Feb 2022 at 17:18, Krishna Narayanan < > > krishnanarayanan132002@xxxxxxxxx> wrote: > > > >> Thanks for your response,Could you please clarify if this is a bug? > >> > > > > It warns with -O1, which is the documented behaviour: > > > > The effectiveness of some warnings depends on optimizations also > > being enabled. For example -Wsuggest-final-types is more > > effective with link-time optimization and -Wmaybe-uninitialized > does > > not warn at all unless optimization is enabled. > > Yes, although the latter sentence is no longer completely accurate. > Since GCC 11 -Wmaybe-uninitialized doesn't need optimization to trigger > for code that passes an uninitialized object to a function that takes > a const reference. Let me update the manual with that. > > > So no, I don't think it' a bug. GCC is behaving as designed. Ideally it > > would be better at warning without optimization, but changing that would > be > > hard. > > It might be tricky to handle this case without causing false positives > in others. > > Krishna, to understand why some of these cases are diagnosed and others > aren't, you need to look at either the dump from the uninit pass > (-fdump-tree-uninit) with -O1 and above, or at some early dump (e.g., > -fdump-tree-ssa) at -O0. Here's a link to the former on Godbolt for > your example: > > https://gcc.godbolt.org/z/89c4s7o6E > > The best way is of course to step through GCC in a debugger (for > the uninitialized warnings the code is in gcc/tree-ssa-uninit.cc). > > Martin > > > > > > > > > > > > >> Regards, > >> Krishna Narayanan. > >> > >> On Tue, Feb 8, 2022 at 10:28 PM Jonathan Wakely <jwakely.gcc@xxxxxxxxx> > >> wrote: > >> > >>> > >>> > >>> On Tue, 8 Feb 2022 at 16:25, Krishna Narayanan via Gcc-help < > >>> gcc-help@xxxxxxxxxxx> wrote: > >>> > >>>> Hello, > >>>> As an extension to the bug 93432 > >>>> (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93432), I would like to > >>>> add a few more points,here in the given code > >>>> (https://godbolt.org/z/sYjqjqh3d) there is a warning averted but > there > >>>> is no warning shown for this code > >>>> (https://gcc.godbolt.org/z/oo5sf4oec) . > >>>> I tried it with "-fno-strict-aliasing -fwrapv > >>>> -fno-aggressive-loop-optimizations" and "fsanitize=undefined".There > >>>> are no errors for gcc but clang has runtime errors,the error for > >>>> clang: https://gcc.godbolt.org/z/1hq8x1o8E . > >>>> > >>>> Can we have a warning in the second case as well? It will be much more > >>>> convenient as there is a lapse of initialization. > >>>> > >>> > >>> Yes, ideally it would warn. > >>> > >>> > >>> > >> > >
