On Wed, May 03, 2023 at 04:13:22PM -0400, Mathieu Desnoyers wrote:
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@xxxxxxxxxxxx>
---
tools/testing/selftests/rseq/compiler.h | 27 +++++++++++++++++++++++++
1 file changed, 27 insertions(+)
diff --git a/tools/testing/selftests/rseq/compiler.h b/tools/testing/selftests/rseq/compiler.h
index f47092bddeba..8dc7f881e253 100644
--- a/tools/testing/selftests/rseq/compiler.h
+++ b/tools/testing/selftests/rseq/compiler.h
@@ -33,4 +33,31 @@
#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
+/*
+ * 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, \
+ unsigned char: (unsigned char)0, \
+ signed char: (signed char)0, \
+ unsigned short: (unsigned short)0, \
+ signed short: (signed short)0, \
+ unsigned int: (unsigned int)0, \
+ signed int: (signed int)0, \
+ unsigned long: (unsigned long)0, \
+ signed long: (signed long)0, \
+ unsigned long long: (unsigned long long)0, \
+ signed long long: (signed long long)0, \
+ default: (x) \
+ ) \
+ )
FWIW, I like how the kernel version uses a little helper for the
signed/unsigned pairs. Makes it a little more readable.
+#endif
+
#endif /* RSEQ_COMPILER_H_ */
--
2.25.1