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Date: Mon, 26 May 2014 16:08:57 -0400
From: Christopher Faylor <cgf-use-the-mailinglist-please AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: Bash silently truncates the Command Line when called programatically via CreateProcess as MAXPATHLEN was reduced to 8192 from 16384
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On Mon, May 26, 2014 at 08:59:56PM +0530, Abhijit Bhattacharjee wrote:
>On a typical configuration, we use gmake on windows as the build
>system. GMAKE calls the Cygwin bash in order to invoke the MSVS
>compiler in-order to satisfy the dependency if a rule to call the
>compiler is present.

If you're using Cygwin's make it will not truncate paths if it is
running cygwin programs.  Not sure what MSVS is.

>Now, for certain modules, the command line was seemingly getting
>truncated. On investigating further it revealed the reason for the
>truncation was because in the glob.cc, MAXPATHLEN was now defined as
>8192 so, when bash was compiled with the changed crt code, the problem
>started to emerge.
>
>Now, it also seems that there was a discussion
>(https://cygwin.com/ml/cygwin-patches/2012-q1/msg00037.html) where
>Corinna mentioned about decreasing the size to 4096 and later
>increasing it to 8192. Unfortunately, for our case, 8192 is low a
>limit and ideally the previous limit of 16384 was working perfectly.
>
>The Argument that Corinna placed was because the default stack size is
>2 Megs  and sizeof(Char)==8, a local array of 8* 16384  would be too
>strenuous for the stack.
>
>It was still not clear to me as to why?
>
>1. The Temporary buffer was not allocated on heap?

The source code comes from FreeBSD.   Managing this on the heap would
mean a rewrite and would have its own problems.  Since this isn't really
an issue when Cygwin calls Cygwin programs it likely isn't really high
on anyone's priority list.

>2. Why the entire argument (both quoted and non-quoted string) was
>passed to the glob module. If instead, the argument string could had
>been tokeinized  as interleaving quoted and non-quoted string, the
>restriction imposed on the argument length would be alleviated. What I
>am envisaging is, currently in the globify module, you are escaping
>all the quoted characters to demarcate from the non-quoted characters
>before calling glob once, so that the glob can only expand non-quoted
>sub-string. Instead, if we could call glob multiple times whenever we
>encounter a sub-string of non-quoted string, wouldn't it be cleaner?

I don't really know what you're talking about but patches are always
better than word descriptions.

It sounds like you're using a non-Cygwin make to call a Cygwin process.
If that is the case then it seems like the trivial fix is "Don't Do
That" (tm)

cgf

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