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Use memcpy for unaligned reads to appease UBSan #7

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67 changes: 22 additions & 45 deletions src/fpng.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -51,14 +51,6 @@
#define FPNG_DISABLE_DECODE_CRC32_CHECKS (0)
#endif

// Using unaligned loads and stores causes errors when using UBSan. Jam it off.
#if defined(__has_feature)
#if __has_feature(undefined_behavior_sanitizer)
#undef FPNG_USE_UNALIGNED_LOADS
#define FPNG_USE_UNALIGNED_LOADS (0)
#endif
#endif

// Set to 0 if your platform doesn't support unaligned 32-bit/64-bit reads/writes.
#ifndef FPNG_USE_UNALIGNED_LOADS
#if FPNG_X86_OR_X64_CPU
Expand Down Expand Up @@ -129,56 +121,41 @@ namespace fpng
#endif
}

#if FPNG_USE_UNALIGNED_LOADS
#if __BYTE_ORDER == __BIG_ENDIAN
#define READ_LE32(p) swap32(*reinterpret_cast<const uint32_t *>(p))
#define WRITE_LE32(p, v) *reinterpret_cast<uint32_t *>(p) = swap32((uint32_t)(v))
#define WRITE_LE64(p, v) *reinterpret_cast<uint64_t *>(p) = swap64((uint64_t)(v))

#define READ_BE32(p) *reinterpret_cast<const uint32_t *>(p)
#else
#define READ_LE32(p) (*reinterpret_cast<const uint32_t *>(p))
#define WRITE_LE32(p, v) *reinterpret_cast<uint32_t *>(p) = (uint32_t)(v)
#define WRITE_LE64(p, v) *reinterpret_cast<uint64_t *>(p) = (uint64_t)(v)

#define READ_BE32(p) swap32(*reinterpret_cast<const uint32_t *>(p))
#endif
#else
// A good compiler should be able to optimize these routines - hopefully. They are crucial for performance.
static inline uint32_t READ_LE32(const void* p)
{
const uint8_t* pBytes = (const uint8_t*)p;
return ((uint32_t)pBytes[0]) | (((uint32_t)pBytes[1]) << 8U) | (((uint32_t)pBytes[2]) << 16U) | (((uint32_t)pBytes[3]) << 24U);
uint32_t result;
memcpy(&result, p, sizeof(result));
#if __BYTE_ORDER == __BIG_ENDIAN
result = swap32(result);
#endif
return result;
}

static inline uint32_t READ_BE32(const void* p)
{
const uint8_t* pBytes = (const uint8_t*)p;
return ((uint32_t)pBytes[3]) | (((uint32_t)pBytes[2]) << 8U) | (((uint32_t)pBytes[1]) << 16U) | (((uint32_t)pBytes[0]) << 24U);
uint32_t result;
memcpy(&result, p, sizeof(result));
#if __BYTE_ORDER == __LITTLE_ENDIAN
result = swap32(result);
#endif
return result;
}

static inline void WRITE_LE32(const void* p, uint32_t v)
static inline void WRITE_LE32(void* p, uint32_t v)
{
uint8_t* pBytes = (uint8_t*)p;
pBytes[0] = (uint8_t)(v);
pBytes[1] = (uint8_t)(v >> 8);
pBytes[2] = (uint8_t)(v >> 16);
pBytes[3] = (uint8_t)(v >> 24);
#if __BYTE_ORDER == __BIG_ENDIAN
v = swap32(v);
#endif
memcpy(p, &v, sizeof(v));
}

static inline void WRITE_LE64(const void* p, uint64_t v)
static inline void WRITE_LE64(void* p, uint64_t v)
{
uint8_t* pBytes = (uint8_t*)p;
pBytes[0] = (uint8_t)(v);
pBytes[1] = (uint8_t)(v >> 8);
pBytes[2] = (uint8_t)(v >> 16);
pBytes[3] = (uint8_t)(v >> 24);
pBytes[4] = (uint8_t)(v >> 32);
pBytes[5] = (uint8_t)(v >> 40);
pBytes[6] = (uint8_t)(v >> 48);
pBytes[7] = (uint8_t)(v >> 56);
}
#if __BYTE_ORDER == __BIG_ENDIAN
v = swap64(v);
#endif
memcpy(p, &v, sizeof(v));
}

// Customized the very common case of reading a 24bpp pixel from memory
static inline uint32_t READ_RGB_PIXEL(const void* p)
Expand Down