On Wed, Jul 26, 2023 at 5:36 PM Jason Merrill <ja...@redhat.com> wrote: > > On 6/30/23 18:59, Lewis Hyatt wrote: > > In order to support processing #pragma in preprocess-only mode (-E or > > -save-temps for gcc/g++), we need a way to obtain the #pragma tokens from > > libcpp. In full compilation modes, this is accomplished by calling > > pragma_lex (), which is a symbol that must be exported by the frontend, and > > which is currently implemented for C and C++. Neither of those frontends > > initializes its parser machinery in preprocess-only mode, and consequently > > pragma_lex () does not work in this case. > > > > Address that by adding a new function c_init_preprocess () for the frontends > > to implement, which arranges for pragma_lex () to work in preprocess-only > > mode, and adjusting pragma_lex () accordingly. > > > > In preprocess-only mode, the preprocessor is accustomed to controlling the > > interaction with libcpp, and it only knows about tokens that it has called > > into libcpp itself to obtain. Since it still needs to see the tokens > > obtained by pragma_lex () so that they can be streamed to the output, also > > add a new libcpp callback, on_token_lex (), that ensures the preprocessor > > sees these tokens too. > > > > Currently, there is one place where we are already supporting #pragma in > > preprocess-only mode, namely the handling of `#pragma GCC diagnostic'. That > > was done by directly interfacing with libcpp, rather than making use of > > pragma_lex (). Now that pragma_lex () works, that code is no longer > > necessary; remove it. > > > > gcc/c-family/ChangeLog: > > > > * c-common.h (c_init_preprocess): Declare new function. > > * c-opts.cc (c_common_init): Call it. > > * c-pragma.cc (pragma_diagnostic_lex_normal): Rename to... > > (pragma_diagnostic_lex): ...this. > > (pragma_diagnostic_lex_pp): Remove. > > (handle_pragma_diagnostic_impl): Call pragma_diagnostic_lex () in > > all modes. > > (c_pp_invoke_early_pragma_handler): Adapt to support pragma_lex () > > usage. > > * c-pragma.h (pragma_lex_discard_to_eol): Declare new function. > > > > gcc/c/ChangeLog: > > > > * c-parser.cc (pragma_lex): Support preprocess-only mode. > > (pragma_lex_discard_to_eol): New function. > > (c_init_preprocess): New function. > > > > gcc/cp/ChangeLog: > > > > * parser.cc (c_init_preprocess): New function. > > (maybe_read_tokens_for_pragma_lex): New function. > > (pragma_lex): Support preprocess-only mode. > > (pragma_lex_discard_to_eol): New funtion. > > > > libcpp/ChangeLog: > > > > * include/cpplib.h (struct cpp_callbacks): Add new callback > > on_token_lex. > > * macro.cc (cpp_get_token_1): Support new callback. > > --- > > > > Notes: > > Hello- > > > > In r13-1544, I added support for processing `#pragma GCC diagnostic' in > > preprocess-only mode. Because pragma_lex () doesn't work in that mode, > > in > > that patch I called into libcpp directly to obtain the tokens needed to > > process the pragma. As part of the review, Jason noted that it would > > probably be better to make pragma_lex () usable in preprocess-only > > mode, and > > we decided just to add a comment about that for the time being, and to > > go > > ahead and implement that in the future, if it became necessary to > > support > > other pragmas during preprocessing. > > > > I think now is a good time to proceed with that plan, because I would > > like > > to fix PR87299, which is about another pragma (#pragma GCC target) not > > working in preprocess-only mode. This patch makes the necessary > > changes for > > pragma_lex () to work in preprocess-only mode. > > > > I have also added a new callback, on_token_lex (), to libcpp. This is > > so the > > preprocessor can see and stream out all the tokens that pragma_lex () > > gets > > from libcpp, since it won't otherwise see them. This seemed the > > simplest > > approach to me. Another possibility would be to add a wrapper function > > in > > c-family/c-lex.cc, which would call cpp_get_token_with_location(), and > > then > > also stream the token in preprocess-only mode, and then change all > > calls > > into libcpp in that file to use the wrapper function. The libcpp > > callback > > seemed cleaner to me FWIW. > > I think the other way sounds better to me; there are only three calls to > cpp_get_... in c_lex_with_flags. > > The rest of the patch looks good.
Thank you very much for the feedback. I will test it this way and send the updated version. -Lewis
