* Richard Biener: > > Am 09.05.2023 um 18:13 schrieb David Edelsohn <dje....@gmail.com>: > > > > On Tue, May 9, 2023 at 12:07 PM Jakub Jelinek via Gcc <gcc@gcc.gnu.org> > > wrote: > > > > On Tue, May 09, 2023 at 05:16:19PM +0200, Richard Biener via Gcc wrote: > > > > > > > > > > Am 09.05.2023 um 14:16 schrieb Florian Weimer via Gcc <gcc@gcc.gnu.org>: > > > > > > > > TL;DR: This message is about turning implicit-int, > > > > implicit-function-declaration, and possibly int-conversion into errors > > > > for GCC 14. > > > > > > I suppose the goal is to not need to rely on altering CFLAGS but > > > change the default behavior with still being able to undo this > > > using -Wno-error= or -Wno-? > > > > Can't people just compile C89/K&R code with -std=c89/-std=gnu89 and not get > > these errors that way? > > > > As Florian mentioned: > > > > "Presently, we > > cannot use -std=gnu89 etc. to opt out because there are packages which > > require both C89-only language features and C99-style inlining, which is > > currently not a combination supported by GCC (but maybe that could be > > changed). " > > But surely it would reduce the number of packages to fix? So I > support both having only C99 and up reject no longer valid code _and_ > having -fpermissive be forgiving (demoting errors to warnings).
It makes sense to disable the new erros in C89 mode. It's what I did in the instrumented compiler. It also gives you yet another way to disable the errors, using CC=c89, which works for some packages that do not honor CFLAGS and do not support whitespace in CC. The part David quoted above is about this: $ gcc -fno-gnu89-inline -std=gnu89 t.c cc1: error: ‘-fno-gnu89-inline’ is only supported in GNU99 or C99 mode And some packages need -fno-gnu89-inline, but also rely on implicit ints and implicit function declarations heavily. With a purely C89-based opt-out and the -fno-gnu89-inline limitation, we wouldn't have a way to compile these self-contradictory programs. Hence the idea of -fpermissive, in addition to the -std=gnu89 escape hatch. But perhaps the -fno-gnu89-inline limitation is easy to eliminate. The remaining reason for -fpermissive would be a flag that is accepted by both gcc and g++, in case a package build system passes CFLAGS to g++ as well, which sometimes happens. And -fno-gnu89-inline is currently not accepted by g++. But in the Fedora package set, this (some C++ and a C89 requirement) must be exceedingly rare because it's a subset of the already tiny set of -fno-gnu89-inline -std=gnu89 packages. Thanks, Florian
