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assert.h: Check overflow with STRICT_ADD, STRICT_SUB

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This commit is contained in:
Justin M. Keyes 2019-01-08 00:22:57 +01:00
parent eaabec459a
commit 6b6a4d63ec
1 changed files with 31 additions and 0 deletions
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31
src/nvim/assert.h
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@ -15,6 +15,10 @@
# define __has_extension __has_feature
#endif
#ifndef __has_builtin
# define __has_builtin __has_feature
#endif
/// @def STATIC_ASSERT
/// @brief Assert at compile time if condition is not satisfied.
///
@ -121,4 +125,31 @@
((enum { ASSERT_CONCAT(assert_line_, __LINE__) = 1/(!!(e)) }) 0)
#endif
/// @def STRICT_ADD
///
/// Requires GCC 5+ and Clang 3.8+
/// https://clang.llvm.org/docs/LanguageExtensions.html
/// https://gcc.gnu.org/onlinedocs/gcc/Integer-Overflow-Builtins.html
///
/// Alternative for compilers without __builtin_xx_overflow ?
/// https://stackoverflow.com/a/44830670/152142
///
/// @param MAX Maximum value of the narrowest type of operand.
/// Not used if compiler supports __builtin_add_overflow.
#if __has_builtin(__builtin_add_overflow)
# define STRICT_ADD(a, b, c) \
do { if (__builtin_add_overflow(a, b, c)) { abort(); } } while (0)
#else
# define STRICT_ADD(a, b, c) \
do { *c = a + b; } while (0)
#endif
#if __has_builtin(__builtin_sub_overflow)
# define STRICT_SUB(a, b, c) \
do { if (__builtin_sub_overflow(a, b, c)) { abort(); } } while (0)
#else
# define STRICT_SUB(a, b, c) \
do { *c = a - b; } while (0)
#endif
#endif // NVIM_ASSERT_H