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Re: Windows select fails with 7.34.0 and 7.35.0 using multi_perform

From: Daniel Stenberg <>
Date: Sun, 16 Feb 2014 23:26:10 +0100 (CET)

On Sat, 15 Feb 2014, Alan wrote:

> I have been able to reproduce the issue with multi-single.c
> System and compile info:
> Windows 7-64 pro
> libCurl compiled using Makefile.m32 and MinGW G++ 4.8.0
> App compiled with G++ 4.8.0 and created a 32bit app.
> Here is the logging output from Msys: Note I have pasted the modified
> multi-single.c after the logging output Please help me understand what is
> going wrong. This modified multi-single.c works with 7.33.0 and fails with
> 7.34.0 and 7.35.0

I translated your test recipe into plain C and made it build on my 64bit
Linux, but it works just fine here! :-/

So, I suggest two ways forward for you:

1 - one way is to bisect to find the offending single commit that actually
broke this for you. This may or may not be useful for us to see exactly what
code that changed that broke it.

2 - if you single-step into the library when the curl_multi_fdset() is called
that returns the bitset that subsequently makes your select() function return
an error, and investigate what it does and what bits it sets and what values
it returns etc. The function does a set of actions depending on the state of
the individual easy handles in use.

List admin:
Received on 2014-02-16