Jeff King [off-list ref] writes:
That made me wonder if we could repeatedly reuse a buffer attached to
the file descriptor. And indeed, isn't that what stdio is? The whole
reason this buffer exists is because we are using a direct descriptor
write. If we switched this function to use fprintf(), we'd avoid the
whole buffer question, have a fixed cap on our memory use (since we just
flush anytime the buffer is full) _and_ we'd reduce the number of
write syscalls we're making by almost a factor of 100.
The primary reason why we avoid stdio in the lower level part of I/O
is that the error reporting and handling is horrible.
e.g. c.f. http://article.gmane.org/gmane.comp.version-control.git/27019
Otherwise, I'd agree with your "Why aren't we using stdio if
counting and avoiding overflow is so hard?".