Fix memchr with a zero length.
The memchr implementation for 64 bit fails if these conditions occur:
- The buffer is 32 byte aligned.
- The buffer contains the character in the first byte.
- The count sent in is zero.
The function should return NULL, but it's not.
Bug: 16676625
(cherry picked from commit e03e1eac0b7682884b6628df1305d34299680cb4)
Change-Id: Ie4cca2c445127a0936ee2b96651a8e7204fbaffd
diff --git a/libc/arch-arm64/generic/bionic/memchr.S b/libc/arch-arm64/generic/bionic/memchr.S
index fbb00ca..e5ea57d 100644
--- a/libc/arch-arm64/generic/bionic/memchr.S
+++ b/libc/arch-arm64/generic/bionic/memchr.S
@@ -75,6 +75,7 @@
* Magic constant 0x40100401 allows us to identify which lane matches
* the requested byte.
*/
+ cbz cntin, .Lzero_length
mov wtmp2, #0x0401
movk wtmp2, #0x4010, lsl #16
dup vrepchr.16b, chrin
@@ -157,4 +158,8 @@
/* Select result or NULL */
csel result, xzr, result, eq
ret
+
+.Lzero_length:
+ mov result, xzr
+ ret
END(memchr)
diff --git a/tests/string_test.cpp b/tests/string_test.cpp
index bc2c05b..73c94c6 100644
--- a/tests/string_test.cpp
+++ b/tests/string_test.cpp
@@ -763,6 +763,14 @@
}
}
+TEST(string, memchr_zero) {
+ uint8_t* buffer;
+ ASSERT_EQ(0, posix_memalign(reinterpret_cast<void**>(&buffer), 64, 64));
+ memset(buffer, 10, 64);
+ ASSERT_TRUE(NULL == memchr(buffer, 5, 0));
+ ASSERT_TRUE(NULL == memchr(buffer, 10, 0));
+}
+
TEST(string, memrchr) {
int seek_char = random() & 255;
StringTestState<char> state(SMALL);