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selftests/rseq: Implement rseq_unqual_scalar_typeof

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Allow defining variables and perform cast with a typeof which removes
the volatile and const qualifiers.

This prevents declaring a stack variable with a volatile qualifier
within a macro, which would generate sub-optimal assembler.

This is imported from the "librseq" project.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
This commit is contained in:
Mathieu Desnoyers 2023-06-27 11:29:21 -04:00 committed by Shuah Khan
parent c0d87e43a6
commit d6aaa23a2b
1 changed files with 26 additions and 0 deletions
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26
tools/testing/selftests/rseq/compiler.h
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@ -33,4 +33,30 @@
#define RSEQ_COMBINE_TOKENS(_tokena, _tokenb) \
RSEQ__COMBINE_TOKENS(_tokena, _tokenb)
#ifdef __cplusplus
#define rseq_unqual_scalar_typeof(x) \
std::remove_cv<std::remove_reference<decltype(x)>::type>::type
#else
#define rseq_scalar_type_to_expr(type) \
unsigned type: (unsigned type)0, \
signed type: (signed type)0
/*
* Use C11 _Generic to express unqualified type from expression. This removes
* volatile qualifier from expression type.
*/
#define rseq_unqual_scalar_typeof(x) \
__typeof__( \
_Generic((x), \
char: (char)0, \
rseq_scalar_type_to_expr(char), \
rseq_scalar_type_to_expr(short), \
rseq_scalar_type_to_expr(int), \
rseq_scalar_type_to_expr(long), \
rseq_scalar_type_to_expr(long long), \
default: (x) \
) \
)
#endif
#endif /* RSEQ_COMPILER_H_ */