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Date: Fri, 27 Aug 2010 14:30:43 +0100
From: Jon TURNEY <jon DOT turney AT dronecode DOT org DOT uk>
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To: cygwin AT cygwin DOT com
Subject: Re: problem with PATH set by libtool for uninstalled pixman library
References: <4C5075E3 DOT 9020903 AT dronecode DOT org DOT uk> <4C5139CD DOT 3010702 AT cwilson DOT fastmail DOT fm>
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On 29/07/2010 09:20, Charles Wilson wrote:
> On 7/28/2010 2:24 PM, Jon TURNEY wrote:
>>
>> I have a tinderbox which does daily builds of the X.Org stack for
>> cygwin, and I've come across a something I don't understand with the way
>> libtool is working when building the pixman library, and I hope someone
>> can shed a bit of light.
>
>
>> (lt_update_lib_path) modifying 'PATH' by prepending
>> '/opt/jhbuild/build/pixman/pixman/.libs:'
>> (lt_setenv) setting 'PATH' to
>> '/opt/jhbuild/build/pixman/pixman/.libs:/home/jon/bin:/usr/local/bin:/usr/bin:/bin:/cygdrive/c/Windows/system32:/cygdrive/c/Windows:/cygdrive/c/Windows/System32/Wbem:/cygdrive/c/Windows/System32/WindowsPowerShell/v1.0/:/bin'
>>
>> (lt_update_exe_path) modifying 'PATH' by prepending
>> '/opt/jhbuild/install/lib:/opt/jhbuild/install/bin:/opt/jhbuild/build/pixman/pixman/.libs:'
>>
>> (lt_setenv) setting 'PATH' to
>> '/opt/jhbuild/install/lib:/opt/jhbuild/install/bin:/opt/jhbuild/build/pixman/pixman/.libs:/opt/jhbuild/build/pixman/pixman/.libs:/home/jon/bin:/usr/local/bin:/usr/bin:/bin:/cygdrive/c/Windows/system32:/cygdrive/c/Windows:/cygdrive/c/Windows/System32/Wbem:/cygdrive/c/Windows/System32/WindowsPowerShell/v1.0/:/bin'
>
> This is because the wrapper prepends the rpath onto $$LIB_PATH_VARNAME,
> and prepends the dllsearchpath onto $$EXE_PATH_VARNAME.
>
> But, since LIB_PATH_VARNAME==EXE_PATH_VARNAME on cygwin (both are
> "PATH") that's basically saying:
>
> PATH=$rpath:${PATH}
> PATH=$dllsearchpath:${PATH}
>
> I think it was a deliberate choice (e.g. on linux) for the wrapper to
> add the $rpath to $LD_RUN_PATH, but...it's not such a great idea for win32.
>
> This is a case where the wrapper exe was trying to do exactly what the
> wrapper script used to do -- without considering whether the wrapper
> script was doing the right thing, for this platform.
>
> I think a patch to simply swap the order of these two assignments would
> be fine (e.g. do $dllsearchpath first, then make sure it gets pre-empted
> by $rpath). On *nix it wouldn't matter, since the two variables are
> DISTINCT vars.

Okay, thanks very much for the explanation.  This clarifies for me that this 
is a bug or platform quirk with libtool, and not something that pixman is 
doing wrong, so I can stick with the workaround I have for the moment.

I don't think I'm feeling brave enough at the moment to look at the libtool 
source:-)

>> As you can see, the install path appears before .libs in the PATH the
>> libtool wrapper constructs, so the installed version from a previous
>> build is used, rather than the uninstalled version we want to test.
>>
>> I'm not quite clear why the install path is being added at all, I don't
>> think libpixman has any dependencies which it needs to find there (at
>> least in the cygwin build)
>
> But libtool doesn't know that, at that particular point in the code.

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