2011/8/1 Marc Glisse <marc.gli...@inria.fr>: > On Fri, 15 Jul 2011, Ian Lance Taylor wrote: > >> I would like to propose this patch as a step toward building gcc using a >> C++ compiler. This patch builds stage1 with the C compiler as usual, >> and defaults to building stages 2 and 3 with a C++ compiler built during >> stage 1. This means that the gcc installed and used by most people will >> be built by a C++ compiler. This will ensure that gcc is fully >> buildable with C++, while retaining the ability to bootstrap with only a >> C compiler, not a C++ compiler. > > Nice step. Now that gcc can (mostly) build with g++, it would be great if it > could build with a non-gnu compiler. More precisely, with a compiler that > doesn't define __GNUC__. Indeed, the code is quite different in this case, > as can be seen trying to compile gcc with CC='gcc -U__GNUC__' and CXX='g++ > -U__GNUC__' (there are other reasons why this won't work, but at least it > shows some of the same issues I see with sunpro). > > > To start with, the obstack_free macro casts a pointer to an int -> error. > /data/repos/gcc/trunk/libcpp/directives.c:2048:7: error: cast from ‘char*’ > to ‘int’ loses precision [-fpermissive] > > > Then, ENUM_BITFIELD(cpp_ttype) is expanded to unsigned int instead of the > enum, and conversions from int to enum require an explicit cast in C++, > giving many errors like: > /data/repos/gcc/trunk/libcpp/charset.c:1615:79: error: invalid conversion > from ‘unsigned int’ to ‘cpp_ttype’ [-fpermissive] > /data/repos/gcc/trunk/libcpp/charset.c:1371:1: error: initializing > argument 5 of ‘bool cpp_interpret_string(cpp_reader*, const cpp_string*, > size_t, cpp_string*, cpp_ttype)’ [-fpermissive] > > Do we want to add a cast in almost every place a field declared with > ENUM_BITFIELD is used? That's quite a lot of places, everywhere in gcc... > The alternative would be to store the full enum instead of a bitfield (just > for stage1 so that's not too bad), but some comments in the code seem to > advise against it.
I think it's the only viable solution (use the full enum for a non-GCC stage1 C++ compiler). We could help it somewhat by at least placing enum bitfields first/last in our bitfield groups. Any other opinions? Btw, thanks for trying non-GCC stage1 compilers ;) Richard.
