[libcxx-commits] [libcxx] [libc++] Add a few _LIBCPP_ASSERT_INTERNALs to make sure internal invariants are kept (PR #114575)

Vitaly Buka via libcxx-commits libcxx-commits at lists.llvm.org
Wed Nov 27 18:46:36 PST 2024


================
@@ -1990,10 +1998,12 @@ private:
   }
 
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pointer __get_long_pointer() _NOEXCEPT {
+    _LIBCPP_ASSERT_INTERNAL(__rep_.__l.__is_long_, "String has to be long when trying to get the long pointer");
     return _LIBCPP_ASAN_VOLATILE_WRAPPER(__rep_.__l.__data_);
   }
 
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 const_pointer __get_long_pointer() const _NOEXCEPT {
+    _LIBCPP_ASSERT_INTERNAL(__rep_.__l.__is_long_, "String has to be long when trying to get the long pointer");
----------------
vitalybuka wrote:

Heads up!

This line (just this like) breaks out tests in  strange way. Code takes impossible branch.

I suspect either UB in this code, or pre-existing miscompile in clang.

Note: 
`_LIBCPP_ASSERT_INTERNAL(__is_long(), ...`
fixes the issue.

Does this ring a bell?


https://github.com/llvm/llvm-project/pull/114575


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