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Avoid invalid gcc 14.3 warning about array bounds in mbedtls_xor #73

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Merged
merged 1 commit into from
Oct 3, 2025
Merged

Avoid invalid gcc 14.3 warning about array bounds in mbedtls_xor #73

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28 changes: 22 additions & 6 deletions library/common.h
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Original file line number Diff line number Diff line change
Expand Up @@ -99,6 +99,13 @@ extern void (*mbedtls_test_hook_test_fail)(const char *test, int line, const cha
* fall back to the unsafe implementation. */
#define ARRAY_LENGTH(array) ARRAY_LENGTH_UNSAFE(array)
#endif

#if defined(__has_builtin)
#define MBEDTLS_HAS_BUILTIN(x) __has_builtin(x)
#else
#define MBEDTLS_HAS_BUILTIN(x) 0
#endif

/** Allow library to access its structs' private members.
*
* Although structs defined in header files are publicly available,
Expand Down Expand Up @@ -208,6 +215,11 @@ static inline void mbedtls_xor(unsigned char *r,
return;
}
#endif
#if defined(MBEDTLS_COMPILER_IS_GCC) && MBEDTLS_HAS_BUILTIN(__builtin_constant_p)
if (__builtin_constant_p(n) && n % 16 == 0) {
return;
}
#endif
#elif defined(MBEDTLS_ARCH_IS_X64) || defined(MBEDTLS_ARCH_IS_ARM64)
/* This codepath probably only makes sense on architectures with 64-bit registers */
for (; (i + 8) <= n; i += 8) {
Expand All @@ -219,6 +231,11 @@ static inline void mbedtls_xor(unsigned char *r,
return;
}
#endif
#if defined(MBEDTLS_COMPILER_IS_GCC) && MBEDTLS_HAS_BUILTIN(__builtin_constant_p)
if (__builtin_constant_p(n) && n % 8 == 0) {
return;
}
#endif
#else
for (; (i + 4) <= n; i += 4) {
uint32_t x = mbedtls_get_unaligned_uint32(a + i) ^ mbedtls_get_unaligned_uint32(b + i);
Expand All @@ -229,6 +246,11 @@ static inline void mbedtls_xor(unsigned char *r,
return;
}
#endif
#if defined(MBEDTLS_COMPILER_IS_GCC) && MBEDTLS_HAS_BUILTIN(__builtin_constant_p)
if (__builtin_constant_p(n) && n % 4 == 0) {
return;
}
#endif
#endif
#endif
for (; i < n; i++) {
Expand Down Expand Up @@ -367,12 +389,6 @@ static inline void mbedtls_xor_no_simd(unsigned char *r,
struct ISO_C_does_not_allow_extra_semicolon_outside_of_a_function
#endif

#if defined(__has_builtin)
#define MBEDTLS_HAS_BUILTIN(x) __has_builtin(x)
#else
#define MBEDTLS_HAS_BUILTIN(x) 0
#endif

/* Define compiler branch hints */
#if MBEDTLS_HAS_BUILTIN(__builtin_expect)
#define MBEDTLS_LIKELY(x) __builtin_expect(!!(x), 1)
Expand Down