On Fri, May 15, 2020 at 3:15 AM Richard Biener <richard.guent...@gmail.com> wrote:
> > +# When bootstrapping with GCC, build stage 1 in C++11 mode to ensure > that a > > +# C++11 compiler can still start the bootstrap. > > if test "$enable_bootstrap:$GXX" = "yes:yes"; then > > + CXX="$CXX -std=gnu++11" > > So I just spotted this - since we're requiring a ISO C++11 compiler > shouldn't > we build stage1 with -std=c++11 rather than gnu++11 (whatever the detailed > differences are here)? Also not sure what level of -pedantic we'd need to > avoid GNU extensions even with -std=c++11. Of course there are (I hope) > a lot less GNU extensions for C++ than there were for C and hopefully > no extra in gnu++11 compared to gnu++98 which we checked previously. > When we first moved to C++ I tried using -std=c++98, but there were too many places where we were assuming that if we're building with GCC, we can use GNU C extensions. I'll see if that's still a problem for -std=c++11. Note I think what's missing is some general blurb in our coding conventions > as to how much of C++11 we are supposed to use in non-infrastructure parts > of GCC (I expect things like hash-table.h to use more C++ features than, > say, tree-ssa-alias.c). > > There also does not seem to be a configure check which may present > users with a more useful error message than later cryptic fail of build? > I suppose we cannot simply check __cplusplus for this, can we? Do > other common host compilers need additional options to enable C++11? > Good point, I'll add that. > Should we try to second guess such flags via configury? For example > GCC 4.8 defaults to -std=gnu++98 and the above only seems to apply > to the bootstrap case so GCC 4.8 cannot be used to build cross compilers > without adjusting CC and CXX? > Older GCC is still GCC and will get the flag automatically. Jason
