Information on a commit related to libstdc++/9533

[Paolo Carlini]

Hi and thanks for your analysis.

>This calls rdbuf()->close(), which calls _M_really_overflow, which
>calls fwrite which should fail because the read end of the pipe
>should have been closed, but since underflow was called at the
>read end, the read end is still open.
>
But, why the testcase didn't fail before reverting the O_NONBLOCK hunk?
The underflow call was there before and it's there now.

Paolo.