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[libc] Fixed mbtowc functions #150118

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Merged
merged 2 commits into from
Jul 22, 2025
Merged

[libc] Fixed mbtowc functions #150118

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4a5a6a6
[libc] Fixed mbtowc functions
Jul 22, 2025
17e737c
added null dest check
Jul 22, 2025
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3 changes: 2 additions & 1 deletion libc/src/__support/wchar/mbrtowc.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -37,7 +37,8 @@ ErrorOr<size_t> mbrtowc(wchar_t *__restrict pwc, const char *__restrict s,
}
auto wc = char_conv.pop_utf32();
if (wc.has_value()) {
*pwc = wc.value();
if (pwc != nullptr)
*pwc = wc.value();
// null terminator -> return 0
if (wc.value() == L'\0')
return 0;
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5 changes: 1 addition & 4 deletions libc/src/wchar/mbtowc.cpp
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Expand Up @@ -25,10 +25,7 @@ LLVM_LIBC_FUNCTION(int, mbtowc,
if (s == nullptr)
return 0;
internal::mbstate internal_mbstate;
// temp ptr to use if pwc is nullptr
wchar_t buf[1];
auto ret =
internal::mbrtowc(pwc == nullptr ? buf : pwc, s, n, &internal_mbstate);
auto ret = internal::mbrtowc(pwc, s, n, &internal_mbstate);
if (!ret.has_value() || static_cast<int>(ret.value()) == -2) {
// Encoding failure
libc_errno = EILSEQ;
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12 changes: 12 additions & 0 deletions libc/test/src/wchar/mbrtowc_test.cpp
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Expand Up @@ -190,6 +190,18 @@ TEST_F(LlvmLibcMBRToWCTest, NullString) {
ASSERT_ERRNO_SUCCESS();
}

TEST_F(LlvmLibcMBRToWCTest, NullDest) {
const char ch[4] = {static_cast<char>(0xF0), static_cast<char>(0x9F),
static_cast<char>(0xA4),
static_cast<char>(0xA1)}; // 🤡 clown emoji
mbstate_t *mb;
LIBC_NAMESPACE::memset(&mb, 0, sizeof(mbstate_t));
// reading nullptr should return correct size
size_t n = LIBC_NAMESPACE::mbrtowc(nullptr, ch, 10, mb);
ASSERT_EQ(static_cast<int>(n), 4);
ASSERT_ERRNO_SUCCESS();
}

TEST_F(LlvmLibcMBRToWCTest, InvalidMBState) {
const char ch[4] = {static_cast<char>(0xC2), static_cast<char>(0x8E),
static_cast<char>(0xC7), static_cast<char>(0x8C)};
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