diff --git a/libc/src/string/string_utils.h b/libc/src/string/string_utils.h index 7feef56fb3676..cbce62ead0328 100644 --- a/libc/src/string/string_utils.h +++ b/libc/src/string/string_utils.h @@ -127,8 +127,8 @@ find_first_character_wide_read(const unsigned char *src, unsigned char ch, size_t cur = 0; // Step 1: read 1 byte at a time to align to block size - for (; reinterpret_cast(char_ptr) % sizeof(Word) != 0 && cur < n; - ++char_ptr, ++cur) { + for (; cur < n && reinterpret_cast(char_ptr) % sizeof(Word) != 0; + ++cur, ++char_ptr) { if (*char_ptr == ch) return const_cast(char_ptr); } @@ -136,18 +136,18 @@ find_first_character_wide_read(const unsigned char *src, unsigned char ch, const Word ch_mask = repeat_byte(ch); // Step 2: read blocks - for (const Word *block_ptr = reinterpret_cast(char_ptr); - !has_zeroes((*block_ptr) ^ ch_mask) && cur < n; - ++block_ptr, cur += sizeof(Word)) { - char_ptr = reinterpret_cast(block_ptr); - } + const Word *block_ptr = reinterpret_cast(char_ptr); + for (; cur < n && !has_zeroes((*block_ptr) ^ ch_mask); + cur += sizeof(Word), ++block_ptr) + ; + char_ptr = reinterpret_cast(block_ptr); // Step 3: find the match in the block - for (; *char_ptr != ch && cur < n; ++char_ptr, ++cur) { + for (; cur < n && *char_ptr != ch; ++cur, ++char_ptr) { ; } - if (*char_ptr != ch || cur >= n) + if (cur >= n || *char_ptr != ch) return static_cast(nullptr); return const_cast(char_ptr); diff --git a/libc/test/src/string/memchr_test.cpp b/libc/test/src/string/memchr_test.cpp index ede841118fe03..a92c5fe80be98 100644 --- a/libc/test/src/string/memchr_test.cpp +++ b/libc/test/src/string/memchr_test.cpp @@ -21,6 +21,11 @@ const char *call_memchr(const void *src, int c, size_t size) { return reinterpret_cast(LIBC_NAMESPACE::memchr(src, c, size)); } +TEST(LlvmLibcMemChrTest, WideReadMultiIteration) { + const char *src = "abcdefghijklmnopqrst$\n"; + ASSERT_STREQ(call_memchr(src, '$', 22), "$\n"); +} + TEST(LlvmLibcMemChrTest, FindsCharacterAfterNullTerminator) { // memchr should continue searching after a null terminator. const size_t size = 5;