[libcxx-commits] [libcxx] [libc++] Ensure that we restore invariants in basic_filebuf::overflow (PR #147389)

[Louis Dionne via libcxx-commits]

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@@ -841,8 +849,9 @@ typename basic_filebuf<_CharT, _Traits>::int_type basic_filebuf<_CharT, _Traits>
 
   if (__always_noconv_) {
     size_t __n = static_cast<size_t>(this->pptr() - this->pbase());
-    if (std::fwrite(this->pbase(), sizeof(char_type), __n, __file_) != __n)
-      return traits_type::eof();
+    if (std::fwrite(this->pbase(), sizeof(char_type), __n, __file_) != __n) {
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ldionne wrote:

The facet for `wchar_t` returns `always_noconv() == false`, so we're also testing below. We could try to hit every branch in the `if` but I think there is diminishing returns.

https://github.com/llvm/llvm-project/pull/147389