[WMS] two consecutive draws using wms layers causes crash in libwww

[assefa]

Way to reproduce :

//open a map containing few wms layers
$poMap = ms_newMapObj("c:/msapps/cwc/htdocs/tes.map");
$img = $poMap->draw();
$url = $img->saveWebImage();

$img = $poMap->draw();
$url = $img->saveWebImage();


The crash seems to happen at a call on HTEventList_loop(request) in
maphttp.c line 251.
It does not happen in mapserver 3.6

[dmorissette]

I've wanted to get rid of libwww for a while already.  It's poorly 
documented and is way too complex for what we need.  I also never found how we 
could ever do POST requests with libwww and we'll need that eventually for WFS. 
I think this will be the excuse to do it.

I've found libcurl that seems perfect for what we need and seems much simpler at 
first sight (http://curl.haxx.se/libcurl/c/).  I'll set this to P1 for 3.7 and 
will try to do it next week.

Note that we'll need to use the 'multi' interface for simultaneous downloads and 
this seems to be available only in recent (7.9.6+) version of the library:
http://curl.haxx.se/libcurl/c/libcurl-multi.html

[dmorissette]

See also bug 243 about some configure problems with the '--with-wmsclient' 
switch.  Both bugs should be addressed at the same time.

[dmorissette]

Bug 247 is also related to libwww and should go away with the new libcurl.

[dmorissette]

I committed the changes to use libcurl instead of libwww to the 3.7 CVS tree.

We'll keep this bug open until:
 1- this has been tested on Windows
 2- The WMS client HOWTO is updated to reflect this change

[assefa]

Closing bug. Tested on windows and the WMS client mentions the use of libcurl 
library.