https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114007
Jakub Jelinek <jakub at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |rsandifo at gcc dot gnu.org --- Comment #13 from Jakub Jelinek <jakub at gcc dot gnu.org> --- Ah, the thing is that while in -std=gnu* modes or -std=c23 the preprocessor recognizes CPP_SCOPE as one token, in -std=c{89,99,11,17} modes it doesn't, :: are 2 CPP_COLONs. So, we could either: --- gcc/c-family/c-lex.cc.jj 2024-01-03 12:07:02.171734141 +0100 +++ gcc/c-family/c-lex.cc 2024-02-21 14:30:37.247945782 +0100 @@ -357,7 +357,24 @@ c_common_has_attribute (cpp_reader *pfil do nxt_token = cpp_peek_token (pfile, idx++); while (nxt_token->type == CPP_PADDING); - if (nxt_token->type == CPP_SCOPE) + if (!c_dialect_cxx () + && flag_iso + && !flag_isoc23 + && nxt_token->type == CPP_COLON) + { + do + nxt_token = cpp_peek_token (pfile, idx++); + while (nxt_token->type == CPP_PADDING); + if (nxt_token->type == CPP_COLON) + { + /* __has_attribute (vendor::attr) in -std=c17 etc. modes. + :: isn't CPP_SCOPE in there and [[vendor::attr]] will + not work, only [[__extension__ vendor::attr]]. */ + have_scope = true; + get_token_no_padding (pfile); // Eat first colon. + } + } + if (nxt_token->type == CPP_SCOPE || have_scope) { have_scope = true; get_token_no_padding (pfile); // Eat scope. but then on testcase like: #if __has_c_attribute (gnu::unused) [[gnu::unused]] #endif int i; #if __has_cpp_attribute (gnu::unused) [[gnu::unused]] #endif int j; fails to compile with e.g -std=c11: pr114007.c:2:1: warning: ‘gnu’ attribute ignored [-Wattributes] 2 | [[gnu::unused]] | ^ pr114007.c:2:6: error: expected ‘]’ before ‘:’ token 2 | [[gnu::unused]] | ^ | ] pr114007.c:6:1: warning: ‘gnu’ attribute ignored [-Wattributes] 6 | [[gnu::unused]] | ^ pr114007.c:6:6: error: expected ‘]’ before ‘:’ token 6 | [[gnu::unused]] | ^ | ] or we could force always returning 0 from __has_attribute/__has_cpp_attribute in that case, like: --- gcc/c-family/c-lex.cc.jj 2024-01-03 12:07:02.171734141 +0100 +++ gcc/c-family/c-lex.cc 2024-02-21 14:41:33.768992572 +0100 @@ -357,7 +357,33 @@ c_common_has_attribute (cpp_reader *pfil do nxt_token = cpp_peek_token (pfile, idx++); while (nxt_token->type == CPP_PADDING); - if (nxt_token->type == CPP_SCOPE) + if (!c_dialect_cxx () + && flag_iso + && !flag_isoc23 + && nxt_token->type == CPP_COLON) + { + do + nxt_token = cpp_peek_token (pfile, idx++); + while (nxt_token->type == CPP_PADDING); + if (nxt_token->type == CPP_COLON) + /* __has_attribute (vendor::attr) in -std=c17 etc. modes. + :: isn't CPP_SCOPE in there but 2 CPP_COLON tokens. */ + have_scope = true; + } + if (have_scope) + { + /* [[vendor::attr]] will not work, only + [[__extension__ vendor::attr]] will. Better always return 0 + for scoped attributes. */ + get_token_no_padding (pfile); // Eat first colon. + get_token_no_padding (pfile); // Eat second colon. + nxt_token = get_token_no_padding (pfile); + if (nxt_token->type != CPP_NAME) + cpp_error (pfile, CPP_DL_ERROR, + "attribute identifier required after scope"); + attr_name = NULL_TREE; + } + else if (nxt_token->type == CPP_SCOPE) { have_scope = true; get_token_no_padding (pfile); // Eat scope. The drawback of the second patch is that then users in -std=c{89,99,11,17} modes don't have a way to query whether a certain scoped attribute is supported in the preprocessor if they are aware that they need to use [[__extension__ vendor::attr]] rather then [[vendor::attr]]. On the other side, e.g. in -std=gnu11 -pedantic-errors compilation we give 1 for __has_c_attribute (gnu::unused), but it is still rejected, just with -std=c11 it is rejected even without -Wpedantic. Maybe instead of loose_scope_p we should be using flag_iso && !flag_isoc23 and accept [[vendor: :attr]] in the -std=c{89,99,11,17} modes too (with pedwarn for the [[]] use), and on the other side reject [[__extension__ vendor: :attr]] in -std=c23 or -std=gnu{89,99,11,17} modes, so that people don't feel using 2 colons rather than a scope is correct. And then perhaps go with the first patch rather than second. Joseph/Richard, your thoughts on this?