From 214cf13f17c7177912cc8f9b6c070c4b3a282c36 Mon Sep 17 00:00:00 2001 From: Vladislav Shchapov Date: Wed, 5 Jan 2022 03:23:42 +0500 Subject: [PATCH] Fix endianness bug in write_digit2_separated (#2699) * Fix endianness bug in write_digit2_separated * Move endianness check to compile time if it possible * Turn 8 into a constant --- include/fmt/chrono.h | 10 +++++++++- include/fmt/format.h | 10 +++++++++- 2 files changed, 18 insertions(+), 2 deletions(-) diff --git a/include/fmt/chrono.h b/include/fmt/chrono.h index 908999ab..682efd8d 100644 --- a/include/fmt/chrono.h +++ b/include/fmt/chrono.h @@ -558,7 +558,15 @@ inline void write_digit2_separated(char* buf, unsigned a, unsigned b, auto usep = static_cast(sep); // Add ASCII '0' to each digit byte and insert separators. digits |= 0x3030003030003030 | (usep << 16) | (usep << 40); - memcpy(buf, &digits, 8); + + constexpr const size_t len = 8; + if (const_check(is_big_endian())) { + char tmp[len]; + memcpy(tmp, &digits, len); + std::reverse_copy(tmp, tmp + len, buf); + } else { + memcpy(buf, &digits, len); + } } template FMT_CONSTEXPR inline const char* get_units() { diff --git a/include/fmt/format.h b/include/fmt/format.h index a6f1fdc8..8b789574 100644 --- a/include/fmt/format.h +++ b/include/fmt/format.h @@ -296,10 +296,18 @@ FMT_CONSTEXPR20 auto bit_cast(const From& from) -> To { } inline auto is_big_endian() -> bool { +#ifdef _WIN32 + return false; +#elif defined(__BIG_ENDIAN__) + return true; +#elif defined(__BYTE_ORDER__) && defined(__ORDER_BIG_ENDIAN__) + return __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__; +#else struct bytes { char data[sizeof(int)]; }; return bit_cast(1).data[0] == 0; +#endif } // A fallback implementation of uintptr_t for systems that lack it. @@ -309,7 +317,7 @@ struct fallback_uintptr { fallback_uintptr() = default; explicit fallback_uintptr(const void* p) { *this = bit_cast(p); - if (is_big_endian()) { + if (const_check(is_big_endian())) { for (size_t i = 0, j = sizeof(void*) - 1; i < j; ++i, --j) std::swap(value[i], value[j]); }