[libcxx-commits] [libcxx] [libc++][format] Don't leave the output buffer full after a bulk write (PR #226791)

[Nikolas Klauser via libcxx-commits]

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@@ -250,6 +250,10 @@ class __output_buffer {
       __first += __chunk;
       __n -= __chunk;
     } while (__n);
+
+    // push_back needs a free code unit, which the last chunk may have used.
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philnik777 wrote:

This fix looks incorrect to me. The point of the `__prepare_write()` above is to ensure `__size_` never equals `__capacity_`. So if the condition below is true, the post-condition of `__prepare_write` is incorrect, or the code in the loop above is incorrect in writing more characters than it's supposed to.

https://github.com/llvm/llvm-project/pull/226791