mirror of https://github.com/encounter/SDL.git
stdinc: Add overflow-checking add and multiply for size_t
This can be used to check whether untrusted sizes would cause overflow when used to calculate how much memory is needed. Signed-off-by: Simon McVittie <smcv@collabora.com>
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@ -115,6 +115,12 @@ char *alloca();
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# endif
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#endif
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#ifdef SIZE_MAX
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# define SDL_SIZE_MAX SIZE_MAX
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#else
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# define SDL_SIZE_MAX ((size_t) -1)
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#endif
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/**
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* Check if the compiler supports a given builtin.
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* Supported by virtually all clang versions and recent gcc. Use this
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@ -728,6 +734,60 @@ SDL_FORCE_INLINE void *SDL_memcpy4(SDL_OUT_BYTECAP(dwords*4) void *dst, SDL_IN_B
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return SDL_memcpy(dst, src, dwords * 4);
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}
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/**
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* If a * b would overflow, return -1. Otherwise store a * b via ret
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* and return 0.
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*
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* \since This function is available since SDL 2.24.0.
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*/
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SDL_FORCE_INLINE int SDL_size_mul_overflow (size_t a,
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size_t b,
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size_t *ret)
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{
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if (a != 0 && b > SDL_SIZE_MAX / a) {
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return -1;
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}
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*ret = a * b;
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return 0;
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}
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#if _SDL_HAS_BUILTIN(__builtin_mul_overflow)
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SDL_FORCE_INLINE int _SDL_size_mul_overflow_builtin (size_t a,
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size_t b,
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size_t *ret)
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{
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return __builtin_mul_overflow(a, b, ret) == 0 ? 0 : -1;
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}
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#define SDL_size_mul_overflow(a, b, ret) (_SDL_size_mul_overflow_builtin(a, b, ret))
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#endif
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/**
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* If a + b would overflow, return -1. Otherwise store a + b via ret
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* and return 0.
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*
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* \since This function is available since SDL 2.24.0.
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*/
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SDL_FORCE_INLINE int SDL_size_add_overflow (size_t a,
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size_t b,
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size_t *ret)
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{
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if (b > SDL_SIZE_MAX - a) {
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return -1;
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}
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*ret = a + b;
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return 0;
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}
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#if _SDL_HAS_BUILTIN(__builtin_add_overflow)
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SDL_FORCE_INLINE int _SDL_size_add_overflow_builtin (size_t a,
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size_t b,
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size_t *ret)
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{
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return __builtin_add_overflow(a, b, ret) == 0 ? 0 : -1;
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}
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#define SDL_size_add_overflow(a, b, ret) (_SDL_size_add_overflow_builtin(a, b, ret))
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#endif
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/* Ends C function definitions when using C++ */
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#ifdef __cplusplus
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}
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