Fix result for zero-length non-null conversion.
Bug: None
Test: deleted the xfail half of the test
Change-Id: I1a60d6ef27ebad14de79ac3bc637a6f2280334d8
diff --git a/libc/bionic/mbrtoc32.cpp b/libc/bionic/mbrtoc32.cpp
index c26dd71..74deb40 100644
--- a/libc/bionic/mbrtoc32.cpp
+++ b/libc/bionic/mbrtoc32.cpp
@@ -51,7 +51,21 @@
}
if (n == 0) {
- return 0;
+ // C23 7.30.1 (for each `mbrtoc*` function) says:
+ //
+ // Returns:
+ //
+ // 0 if the next n or fewer bytes complete the multibyte character that
+ // corresponds to the null wide character (which is the value stored).
+ //
+ // (size_t)(-2) if the next n bytes contribute to an incomplete (but
+ // potentially valid) multibyte character, and all n bytes have been
+ // processed (no value is stored).
+ //
+ // Bionic historically interpreted the behavior when n is 0 to be the next 0
+ // bytes decoding to the null. That's a pretty bad interpretation, and both
+ // glibc and musl return -2 for that case.
+ return BIONIC_MULTIBYTE_RESULT_INCOMPLETE_SEQUENCE;
}
uint8_t ch;