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Add MOZ_FALLTHROUGH macro definition for gcc 7 to suppress -Wimplicit-fallthrough warnings

The generic fallback MOZ_FALLTHROUGH definition is insufficient for GCC 7 and above, resulting in build warning spam and --enable-warnings-as-errors builds failing. The check for clang support is changed to use the __has_cpp_attribute macro, which is more robust than checking the __cplusplus version. Also, MOZ_FALLTHROUGH is now only defined in C++ code, since GCC errors out if it encounters a scoped attribute being used with __has_cpp_attribute in C code. No C code uses MOZ_FALLTHROUGH or derivatives at the moment.
pull/1/head
trav90 4 years ago committed by Roy Tam
parent
commit
4a350f434e
  1. 13
      mfbt/Attributes.h

13
mfbt/Attributes.h

@ -256,6 +256,8 @@
# define MOZ_MUST_USE
#endif
#ifdef __cplusplus
/**
* MOZ_FALLTHROUGH is an annotation to suppress compiler warnings about switch
* cases that fall through without a break or return statement. MOZ_FALLTHROUGH
@ -282,9 +284,14 @@
* return 5;
* }
*/
#if defined(__clang__) && __cplusplus >= 201103L
/* clang's fallthrough annotations are only available starting in C++11. */
#ifndef __has_cpp_attribute
# define __has_cpp_attribute(x) 0
#endif
#if __has_cpp_attribute(clang::fallthrough)
# define MOZ_FALLTHROUGH [[clang::fallthrough]]
#elif __has_cpp_attribute(gnu::fallthrough)
# define MOZ_FALLTHROUGH [[gnu::fallthrough]]
#elif defined(_MSC_VER)
/*
* MSVC's __fallthrough annotations are checked by /analyze (Code Analysis):
@ -296,8 +303,6 @@
# define MOZ_FALLTHROUGH /* FALLTHROUGH */
#endif
#ifdef __cplusplus
/*
* The following macros are attributes that support the static analysis plugin
* included with Mozilla, and will be implemented (when such support is enabled)

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