[libc-commits] [libc] [libc][wchar] Fix OOB read and integer underflow in wcslcat and wcsncat (PR #203704)

[via libc-commits]

github-actions[bot] wrote:

<!--PREMERGE ADVISOR COMMENT: Linux-->
# :penguin: Linux x64 Test Results

The build failed before running any tests. Click on a failure below to see the details.

<details>
<summary>libc/test/src/wchar/CMakeFiles/libc.test.src.wchar.wcslcat_test.__unit__.__build__.dir/wcslcat_test.cpp.o</summary>

```
FAILED: libc/test/src/wchar/CMakeFiles/libc.test.src.wchar.wcslcat_test.__unit__.__build__.dir/wcslcat_test.cpp.o
/home/gha/actions-runner/_work/llvm-project/llvm-project/build/./bin/clang++ --target=x86_64-unknown-linux-gnu -DLIBC_NAMESPACE=__llvm_libc_23_0_0_git -I/home/gha/actions-runner/_work/llvm-project/llvm-project/libc -I/home/gha/actions-runner/_work/llvm-project/llvm-project/build/runtimes/runtimes-bins/libc -isystem /home/gha/actions-runner/_work/llvm-project/llvm-project/build/runtimes/runtimes-bins/libc/include -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wno-pass-failed -Wmisleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -Xclang -fno-pch-timestamp -O3 -DNDEBUG -std=gnu++17 -UNDEBUG -D__LIBC_USE_BUILTIN_ISNAN -DLIBC_QSORT_IMPL=LIBC_QSORT_QUICK_SORT -DLIBC_COPT_STRING_LENGTH_IMPL=clang_vector -DLIBC_COPT_FIND_FIRST_CHARACTER_IMPL=word -DLIBC_ADD_NULL_CHECKS -DLIBC_ERRNO_MODE=LIBC_ERRNO_MODE_DEFAULT -DLIBC_THREAD_MODE=LIBC_THREAD_MODE_PLATFORM -DLIBC_COPT_TIMEOUT_ENSURE_MONOTONICITY -DLIBC_CONF_WCTYPE_MODE=LIBC_WCTYPE_MODE_ASCII -DLIBC_COPT_RAW_MUTEX_DEFAULT_SPIN_COUNT=100 -fpie -ffixed-point -Wall -Wextra -Wconversion -Wno-sign-conversion -Wimplicit-fallthrough -Wwrite-strings -Wno-c99-extensions -Wno-gnu-imaginary-constant -Wno-pedantic -Wstrict-prototypes -Wextra-semi -Wnewline-eof -Wnonportable-system-include-path -Wthread-safety -DLIBC_COMPILER_HAS_STDC_FENV_ACCESS -DLIBC_TEST=UNIT -MD -MT libc/test/src/wchar/CMakeFiles/libc.test.src.wchar.wcslcat_test.__unit__.__build__.dir/wcslcat_test.cpp.o -MF libc/test/src/wchar/CMakeFiles/libc.test.src.wchar.wcslcat_test.__unit__.__build__.dir/wcslcat_test.cpp.o.d -o libc/test/src/wchar/CMakeFiles/libc.test.src.wchar.wcslcat_test.__unit__.__build__.dir/wcslcat_test.cpp.o -c /home/gha/actions-runner/_work/llvm-project/llvm-project/libc/test/src/wchar/wcslcat_test.cpp
/home/gha/actions-runner/_work/llvm-project/llvm-project/libc/test/src/wchar/wcslcat_test.cpp:69:2: error: no newline at end of file [-Werror,-Wnewline-eof]
69 | }
|  ^
1 error generated.
```
</details>
<details>
<summary>libc/test/src/wchar/CMakeFiles/libc.test.src.wchar.wcsncat_test.__unit__.__build__.dir/wcsncat_test.cpp.o</summary>

```
FAILED: libc/test/src/wchar/CMakeFiles/libc.test.src.wchar.wcsncat_test.__unit__.__build__.dir/wcsncat_test.cpp.o
/home/gha/actions-runner/_work/llvm-project/llvm-project/build/./bin/clang++ --target=x86_64-unknown-linux-gnu -DLIBC_NAMESPACE=__llvm_libc_23_0_0_git -I/home/gha/actions-runner/_work/llvm-project/llvm-project/libc -I/home/gha/actions-runner/_work/llvm-project/llvm-project/build/runtimes/runtimes-bins/libc -isystem /home/gha/actions-runner/_work/llvm-project/llvm-project/build/runtimes/runtimes-bins/libc/include -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wno-pass-failed -Wmisleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -Xclang -fno-pch-timestamp -O3 -DNDEBUG -std=gnu++17 -UNDEBUG -D__LIBC_USE_BUILTIN_ISNAN -DLIBC_QSORT_IMPL=LIBC_QSORT_QUICK_SORT -DLIBC_COPT_STRING_LENGTH_IMPL=clang_vector -DLIBC_COPT_FIND_FIRST_CHARACTER_IMPL=word -DLIBC_ADD_NULL_CHECKS -DLIBC_ERRNO_MODE=LIBC_ERRNO_MODE_DEFAULT -DLIBC_THREAD_MODE=LIBC_THREAD_MODE_PLATFORM -DLIBC_COPT_TIMEOUT_ENSURE_MONOTONICITY -DLIBC_CONF_WCTYPE_MODE=LIBC_WCTYPE_MODE_ASCII -DLIBC_COPT_RAW_MUTEX_DEFAULT_SPIN_COUNT=100 -fpie -ffixed-point -Wall -Wextra -Wconversion -Wno-sign-conversion -Wimplicit-fallthrough -Wwrite-strings -Wno-c99-extensions -Wno-gnu-imaginary-constant -Wno-pedantic -Wstrict-prototypes -Wextra-semi -Wnewline-eof -Wnonportable-system-include-path -Wthread-safety -DLIBC_COMPILER_HAS_STDC_FENV_ACCESS -DLIBC_TEST=UNIT -MD -MT libc/test/src/wchar/CMakeFiles/libc.test.src.wchar.wcsncat_test.__unit__.__build__.dir/wcsncat_test.cpp.o -MF libc/test/src/wchar/CMakeFiles/libc.test.src.wchar.wcsncat_test.__unit__.__build__.dir/wcsncat_test.cpp.o.d -o libc/test/src/wchar/CMakeFiles/libc.test.src.wchar.wcsncat_test.__unit__.__build__.dir/wcsncat_test.cpp.o -c /home/gha/actions-runner/_work/llvm-project/llvm-project/libc/test/src/wchar/wcsncat_test.cpp
/home/gha/actions-runner/_work/llvm-project/llvm-project/libc/test/src/wchar/wcsncat_test.cpp:109:2: error: no newline at end of file [-Werror,-Wnewline-eof]
109 | }
|  ^
1 error generated.
```
</details>

If these failures are unrelated to your changes (for example tests are broken or flaky at HEAD), please open an issue at https://github.com/llvm/llvm-project/issues and add the `infrastructure` label.

https://github.com/llvm/llvm-project/pull/203704