1 /* SPDX-License-Identifier: LGPL-2.1-only OR MIT */ 2 /* 3 * rseq/compiler.h 4 * 5 * Work-around asm goto compiler bugs. 6 * 7 * (C) Copyright 2021 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com> 8 */ 9 10 #ifndef RSEQ_COMPILER_H 11 #define RSEQ_COMPILER_H 12 13 /* 14 * gcc prior to 4.8.2 miscompiles asm goto. 15 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670 16 * 17 * gcc prior to 8.1.0 miscompiles asm goto at O1. 18 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103908 19 * 20 * clang prior to version 13.0.1 miscompiles asm goto at O2. 21 * https://github.com/llvm/llvm-project/issues/52735 22 * 23 * Work around these issues by adding a volatile inline asm with 24 * memory clobber in the fallthrough after the asm goto and at each 25 * label target. Emit this for all compilers in case other similar 26 * issues are found in the future. 27 */ 28 #define rseq_after_asm_goto() asm volatile ("" : : : "memory") 29 30 /* Combine two tokens. */ 31 #define RSEQ__COMBINE_TOKENS(_tokena, _tokenb) \ 32 _tokena##_tokenb 33 #define RSEQ_COMBINE_TOKENS(_tokena, _tokenb) \ 34 RSEQ__COMBINE_TOKENS(_tokena, _tokenb) 35 36 #ifdef __cplusplus 37 #define rseq_unqual_scalar_typeof(x) \ 38 std::remove_cv<std::remove_reference<decltype(x)>::type>::type 39 #else 40 #define rseq_scalar_type_to_expr(type) \ 41 unsigned type: (unsigned type)0, \ 42 signed type: (signed type)0 43 44 /* 45 * Use C11 _Generic to express unqualified type from expression. This removes 46 * volatile qualifier from expression type. 47 */ 48 #define rseq_unqual_scalar_typeof(x) \ 49 __typeof__( \ 50 _Generic((x), \ 51 char: (char)0, \ 52 rseq_scalar_type_to_expr(char), \ 53 rseq_scalar_type_to_expr(short), \ 54 rseq_scalar_type_to_expr(int), \ 55 rseq_scalar_type_to_expr(long), \ 56 rseq_scalar_type_to_expr(long long), \ 57 default: (x) \ 58 ) \ 59 ) 60 #endif 61 62 #endif /* RSEQ_COMPILER_H_ */ 63