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Re: 1.7.8: write fails with EAGAIN


Hang on, you are saying that a *blocking* write(2) to a pipe returns
with EAGAIN?  Are you sure?  It would be quite a surprise if git would
actually do that.  EAGAIN is only an expected error for non-blocking
I/O, so applications which use blocking I/O usually only test for EINTR.

I checked out the winsup sources and built a cygwin1.dll for debugging (btw: Could you update the FAQ to state that gcc4 is required instead of gcc?).

What I found out:

In, write_overlapped, there is the call to WriteFile:

	bool res = WriteFile (get_output_handle (), ptr, len, &nbytes,
			      get_overlapped ());

Surprisingly, this returns FALSE / nbytes = 0 / GetLastError = ERROR_INVALID_HANDLE on WinXP if the number of bytes exceeds some maximum and the handle refers to a pipe.
Since you don't know what kind of handle you're writing to in write_overlapped, it seems reasonable to do the write in chunks.

The first comment to WriteFile ( suggests to limit the size to less than 32MB per write - although I didn't have this problem on X64.


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