Gcc's '#pragma GCC diagnostic' directives are processed in "early mode" (see handle_pragma_diagnostic_early) for the C++ frontend and, as such, require that the target diagnostic option be enabled for the preprocessor (see c_option_is_from_cpp_diagnostics). This change modifies the -Wc++20-compat option definition to register it as a preprocessor option so that its associated diagnostics can be suppressed. The changes also implicitly disable the option in C++20 and later modes. These changes are consistent with the definition of the -Wc++11-compat option.
This support is motivated by the need to suppress the following diagnostic otherwise issued in C++17 and earlier modes due to the char8_t typedef present in the uchar.h header file in glibc 2.36. warning: identifier ‘char8_t’ is a keyword in C++20 [-Wc++20-compat] Tests are added to validate suppression of both -Wc++11-compat and -Wc++20-compat related diagnostics (fixes were only needed for the C++20 case). Fixes https://gcc.gnu.org/PR106423. gcc/c-family/ChangeLog: * c-opts.cc (c_common_post_options): Disable -Wc++20-compat diagnostics in C++20 and later. * c.opt (Wc++20-compat): Enable hooks for the preprocessor. gcc/testsuite/ChangeLog: * g++.dg/cpp0x/keywords2.C: New test. * g++.dg/cpp2a/keywords2.C: New test. libcpp/ChangeLog: * include/cpplib.h (cpp_warning_reason): Add CPP_W_CXX20_COMPAT. * init.cc (cpp_create_reader): Add cpp_warn_cxx20_compat. --- gcc/c-family/c-opts.cc | 7 +++++++ gcc/c-family/c.opt | 2 +- gcc/testsuite/g++.dg/cpp0x/keywords2.C | 16 ++++++++++++++++ gcc/testsuite/g++.dg/cpp2a/keywords2.C | 13 +++++++++++++ libcpp/include/cpplib.h | 4 ++++ libcpp/init.cc | 1 + 6 files changed, 42 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/g++.dg/cpp0x/keywords2.C create mode 100644 gcc/testsuite/g++.dg/cpp2a/keywords2.C diff --git a/gcc/c-family/c-opts.cc b/gcc/c-family/c-opts.cc index b9f01a65ed7..1ea37ba9742 100644 --- a/gcc/c-family/c-opts.cc +++ b/gcc/c-family/c-opts.cc @@ -1046,6 +1046,13 @@ c_common_post_options (const char **pfilename) else if (warn_narrowing == -1) warn_narrowing = 0; + if (cxx_dialect >= cxx20) + { + /* Don't warn about C++20 compatibility changes in C++20 or later. */ + warn_cxx20_compat = 0; + cpp_opts->cpp_warn_cxx20_compat = 0; + } + /* C++17 has stricter evaluation order requirements; let's use some of them for earlier C++ as well, so chaining works as expected. */ if (c_dialect_cxx () diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt index 44e1a60ce24..dfdebd596ef 100644 --- a/gcc/c-family/c.opt +++ b/gcc/c-family/c.opt @@ -455,7 +455,7 @@ Wc++2a-compat C++ ObjC++ Warning Alias(Wc++20-compat) Undocumented Wc++20-compat -C++ ObjC++ Var(warn_cxx20_compat) Warning LangEnabledBy(C++ ObjC++,Wall) +C++ ObjC++ Var(warn_cxx20_compat) Warning LangEnabledBy(C++ ObjC++,Wall) Init(0) CPP(cpp_warn_cxx20_compat) CppReason(CPP_W_CXX20_COMPAT) Warn about C++ constructs whose meaning differs between ISO C++ 2017 and ISO C++ 2020. Wc++11-extensions diff --git a/gcc/testsuite/g++.dg/cpp0x/keywords2.C b/gcc/testsuite/g++.dg/cpp0x/keywords2.C new file mode 100644 index 00000000000..d67d01e31ed --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp0x/keywords2.C @@ -0,0 +1,16 @@ +// { dg-do compile { target c++98_only } } +// { dg-options "-Wc++11-compat" } + +// Validate suppression of -Wc++11-compat diagnostics. +#pragma GCC diagnostic ignored "-Wc++11-compat" +int alignof; +int alignas; +int constexpr; +int decltype; +int noexcept; +int nullptr; +int static_assert; +int thread_local; +int _Alignas; +int _Alignof; +int _Thread_local; diff --git a/gcc/testsuite/g++.dg/cpp2a/keywords2.C b/gcc/testsuite/g++.dg/cpp2a/keywords2.C new file mode 100644 index 00000000000..8714a7b26b7 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/keywords2.C @@ -0,0 +1,13 @@ +// { dg-do compile { target c++17_down } } +// { dg-options "-Wc++20-compat" } + +// Validate suppression of -Wc++20-compat diagnostics. +#pragma GCC diagnostic ignored "-Wc++20-compat" +int constinit; +int consteval; +int requires; +int concept; +int co_await; +int co_yield; +int co_return; +int char8_t; diff --git a/libcpp/include/cpplib.h b/libcpp/include/cpplib.h index 3eba6f74b57..9d90c18e4f2 100644 --- a/libcpp/include/cpplib.h +++ b/libcpp/include/cpplib.h @@ -547,6 +547,9 @@ struct cpp_options /* True if warn about differences between C++98 and C++11. */ bool cpp_warn_cxx11_compat; + /* True if warn about differences between C++17 and C++20. */ + bool cpp_warn_cxx20_compat; + /* Nonzero if bidirectional control characters checking is on. See enum cpp_bidirectional_level. */ unsigned char cpp_warn_bidirectional; @@ -655,6 +658,7 @@ enum cpp_warning_reason { CPP_W_C90_C99_COMPAT, CPP_W_C11_C2X_COMPAT, CPP_W_CXX11_COMPAT, + CPP_W_CXX20_COMPAT, CPP_W_EXPANSION_TO_DEFINED, CPP_W_BIDIRECTIONAL }; diff --git a/libcpp/init.cc b/libcpp/init.cc index f4ab83d2145..cca3c1dc1e7 100644 --- a/libcpp/init.cc +++ b/libcpp/init.cc @@ -202,6 +202,7 @@ cpp_create_reader (enum c_lang lang, cpp_hash_table *table, CPP_OPTION (pfile, cpp_warn_c90_c99_compat) = -1; CPP_OPTION (pfile, cpp_warn_c11_c2x_compat) = -1; CPP_OPTION (pfile, cpp_warn_cxx11_compat) = 0; + CPP_OPTION (pfile, cpp_warn_cxx20_compat) = 0; CPP_OPTION (pfile, cpp_warn_deprecated) = 1; CPP_OPTION (pfile, cpp_warn_long_long) = 0; CPP_OPTION (pfile, dollars_in_ident) = 1; -- 2.32.0
