diff options
| -rw-r--r-- | config_host/config_global.h.in | 3 | ||||
| -rw-r--r-- | configure.ac | 35 | ||||
| -rw-r--r-- | include/sal/types.h | 8 |
3 files changed, 43 insertions, 3 deletions
diff --git a/config_host/config_global.h.in b/config_host/config_global.h.in index 7913460d6bf8..1c9e610f9167 100644 --- a/config_host/config_global.h.in +++ b/config_host/config_global.h.in @@ -23,6 +23,9 @@ Any change in this header will cause a rebuild of almost everything. /* Compiler supports __attribute__((warn_unused)). */ #define HAVE_GCC_ATTRIBUTE_WARN_UNUSED 0 +/* [[fallthrough]] (C++17), __has_cpp_attribute(fallthrough) (C++2a): */ +#define HAVE_CPP_ATTRIBUTE_FALLTHROUGH 0 + /* [[nodiscard]] (C++17), __has_cpp_attribute(nodiscard) (C++2a): */ #define HAVE_CPP_ATTRIBUTE_NODISCARD 0 diff --git a/configure.ac b/configure.ac index d6560b1d4073..5c0d8a420c23 100644 --- a/configure.ac +++ b/configure.ac @@ -6404,6 +6404,41 @@ if test "$GCC" = yes; then fi AC_SUBST([HAVE_GCC_FNO_SIZED_DEALLOCATION]) +AC_MSG_CHECKING([[whether $CXX supports [[fallthrough]]]]) +AC_LANG_PUSH([C++]) +save_CXXFLAGS=$CXXFLAGS +CXXFLAGS="$CXXFLAGS $CXXFLAGS_CXX11" +dnl Unknown attributes must be ignored by compilers, but they do emit warnings about them: +if test "$COM" = MSC; then + CXXFLAGS="$CXXFLAGS /we5030" +else + CXXFLAGS="$CXXFLAGS -Werror" +fi +AC_COMPILE_IFELSE([AC_LANG_SOURCE([[ + // There appears to be no feature-test macro for __has_cpp_attribute in C++2a, approximate + // by checking for __cplusplus: + #if __cplusplus > 201703L + #if !__has_cpp_attribute(fallthrough) + #error + #endif + #else + void f(int & x) { + switch (x) { + case 0: + ++x; + [[fallthrough]]; + default: + ++x; + } + } + #endif + ]])], [ + AC_DEFINE([HAVE_CPP_ATTRIBUTE_FALLTHROUGH],[1]) + AC_MSG_RESULT([yes]) + ], [AC_MSG_RESULT([no])]) +CXXFLAGS=$save_CXXFLAGS +AC_LANG_POP([C++]) + AC_MSG_CHECKING([[whether $CXX supports [[nodiscard]]]]) AC_LANG_PUSH([C++]) save_CXXFLAGS=$CXXFLAGS diff --git a/include/sal/types.h b/include/sal/types.h index 875f121db1ae..474a223a2ff2 100644 --- a/include/sal/types.h +++ b/include/sal/types.h @@ -422,10 +422,12 @@ namespace css = ::com::sun::star; #endif #if defined LIBO_INTERNAL_ONLY -#if defined __clang__ -#define SAL_FALLTHROUGH [[clang::fallthrough]] -#elif defined __GNUC__ && __GNUC__ >= 7 +#if HAVE_CPP_ATTRIBUTE_FALLTHROUGH #define SAL_FALLTHROUGH [[fallthrough]] +#elif defined __clang__ + /* before Clang 3.9, according to + <https://en.cppreference.com/w/cpp/compiler_support#C.2B.2B17_features> */ +#define SAL_FALLTHROUGH [[clang::fallthrough]] #else #define SAL_FALLTHROUGH #endif |