Re: [Bug-wget] DLL conflict between wget and curl

[David H. Lipman]

From: "Jeremy Nicoll - ml wget users" <address@hidden>

> Win-32 XP Pro SP3
>
> A few hours ago I downloaded cURL, unpacked its zip, and moved the exe and
> necessary DLLs to the folder where I keep CLI programs.  That is:
>
>    curl.exe          659 KB    V7.25.0.0
>    libcurl.dll       529 KB    V7.25.0.0
>    libeay32.dll     1516 KB    no version number
>    libssl32.dll      345 KB    no version number
>
> Then I moved on to do the same for wget.   But the dependencies zip comes
> with 4 DLLs:
>
>    libeay32.dll     1150 KB    V0.9.8.8
>    libiconv2.dll     985 KB    V1.12.2872.39125
>    libintl3.dll      101 KB    V0.14.4.1952
>    libssl32.dll      228 KB    V0.9.8.8
>
> Clearly I can't put the libeay32 & libssl32 DLLs supplied with wget into 
> the
> same folder as the two that came with curl.  And because Windows Explorer
> shows no version number info for the ones that came with curl, I don't 
> know
> which ones are the more recent versions.
>
> Even if I did know that, I don't know whether it's good practice to keep
> each exe with the specific versions of DLLs it was shipped with (though I
> suspect that IS the best method) or whether one should just install the 
> most
> recent version of each libxxxx.dll and hope.
>
> If the DLLs need kept separately then it follows that neither set should 
> be
> in a folder on PATH, and I suppose that neither curl.exe nor wget.exe 
> should
> be either.  Is the solution to this problem to put each app in its own
> folder and alway specify the path to the exe when I want to use it?

Here's what I see in the problem...

When an EXE makes a call to a DLL if it is in the same folder as the 
executable then it loads it.  If it doesn't exist in that folder then it 
will attempt to load the DLL from the PATH.  If the DLL is not found in the 
PATH the program will error out.  This behaviour can be modified by a 
Registry tweak.

The problem occurs when an EXE loads DEPENDENT.DLL version X and is now 
loaded in memory.  Then a second application loads that wants the same DLL 
but expects version Y.  Since the DLL is loaded in memory the second 
application loads without error.  However since version X is loaded not 
version Y when the second application makes a call to a DLL function it does 
not return what is expcted and then second application either does not work 
correctly or it generates an error message.

If it is a case where an EXE loads DEPENDENT.DLL version X and then exits, 
the DEPENDENT.DLL is unloaded.  If it is a case where an EXE loads 
DEPENDENT.DLL version X and stays resident, then you may have problems.


--
Dave
Multi-AV Scanning Tool - http://multi-av.thespykiller.co.uk
http://www.pctipp.ch/downloads/dl/35905.asp