[Bug lto/95190] Documentation for -Wstringop-overflow
stayprivate at gmail dot com
gcc-bugzilla@gcc.gnu.org
Tue May 19 16:29:18 GMT 2020
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95190
--- Comment #4 from Mario Charest <stayprivate at gmail dot com> ---
On Mon, May 18, 2020 at 1:09 PM msebor at gcc dot gnu.org <
gcc-bugzilla@gcc.gnu.org> wrote:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95190
>
> Martin Sebor <msebor at gcc dot gnu.org> changed:
>
> What |Removed |Added
>
> ----------------------------------------------------------------------------
> Last reconfirmed| |2020-05-18
> Status|UNCONFIRMED |WAITING
> Component|c++ |lto
> Ever confirmed|0 |1
> CC| |marxin at gcc dot gnu.org
> ,
> | |msebor at gcc dot gnu.org
> Keywords| |documentation
>
> --- Comment #1 from Martin Sebor <msebor at gcc dot gnu.org> ---
> Which part do you find surprising? That the warning is issued during the
> LTO
> stage at all or that -Wno-stringop-overflow can be used during the LTO
> stage to
> suppress it?
>
Mostly the LTO stage. I got bitten because I assumed warning came from the
compiler. If the LTO stage would have handle #pragma diagnostic i would
have never noticed where it came from.
>
> During LTO the same compiler options should be implicitly enabled as during
> ordinary compilation, including warnings. (This presents some challenges
> when
> the compilation was done with different options for different files.)
>
Most project with cmake using lto will required tweaking. Typically
warning options are specified with add_compiler_options(). Now every
warning flags must also be passed to the linker, impossible to know which
flag has an effect on the LTO stage or not.
> It also means that all the same warnings should be expected to be
> implicitly
> enabled during LTO that were explicitly enabled during the compilation
> stage.
> I'd expect to see only "late" warnings during LTO, i.e., those that depend
> on
> optimization. (I understand this doesn't work completely consistently yet
> but
> I believe that's the goal.)
>
> So this effect isn't specific to -Wstringop-overflow, but perhaps it would
> be
> worth mentioning under -flto?
>
> --
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