The problem is that mime_decode_close() closes all files registered
after mip->mi_pipe_end and this is getting set in mime_sendmessage()
after a fflush().
When you print a large number of messages fflush() blocks and prevents
mip->mi_pipe_end from getting set before the SIGPIPE comes in and
jumps to the close block that calls mime_decode_close(). As a result,
mime_decode_close() was closing all the registered files including
obuf (mi_pipe_end was NULL).
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