+ that we can check it out. Make sure to read \ref faq_bugrepport
+ before you do so.
+
+\subsection faq_trouble_errors Understanding error messages
+
+\subsubsection faq_trouble_err_logcat "gcc: _simgrid_this_log_category_does_not_exist__??? undeclared (first use in this function)"
+
+This is because you are using the log mecanism, but you didn't created
+any default category in this file. You should refer to \ref XBT_log
+for all the details, but you simply forgot to call one of
+XBT_LOG_NEW_DEFAULT_CATEGORY() or XBT_LOG_NEW_DEFAULT_SUBCATEGORY().
+
+\subsubsection faq_flexml_limit "surf_parse_lex: Assertion `next limit' failed."
+
+This is because your platform file is too big for the parser.
+
+Actually, the message comes directly from FleXML, the technology on top of
+which the parser is built. FleXML has the bad idea of fetching the whole
+document in memory before parsing it. And moreover, the memory buffer size
+must be determinded at compilation time.
+
+We use a value which seems big enough for our need without bloating the
+simulators footprints. But of course your mileage may vary. In this case,
+just edit src/surf/surfxml.l modify the definition of
+FLEXML_BUFFERSTACKSIZE. E.g.
+
+\verbatim
+#define FLEXML_BUFFERSTACKSIZE 1000000000
+\endverbatim
+
+Then recompile and everything should be fine, provided that your version of
+Flex is recent enough (>= 2.5.31). If not the compilation process should
+warn you.
+
+A while ago, we worked on FleXML to reduce a bit its memory consumtion, but
+these issues remain. There is two things we should do:
+
+ - use a dynamic buffer instead of a static one so that the only limit
+ becomes your memory, not a stupid constant fixed at compilation time
+ (maybe not so difficult).
+ - change the parser so that it does not need to get the whole file in
+ memory before parsing
+ (seems quite difficult, but I'm a complete newbe wrt flex stuff).
+
+These are changes to FleXML itself, not SimGrid. But since we kinda hijacked
+the development of FleXML, I can grant you that any patches would be really
+welcome and quickly integrated.
+
+<b>Update:</b> A new version of FleXML (1.7) was released. Most of the work
+was done by William Dowling, who use it in his own work. The good point is
+that it now use a dynamic buffer, and that the memory usage was greatly
+improved. The downside is that William also changed some things internally,
+and it breaks the hack we devised to bypass the parser, as explained in
+\ref faq_flexml_bypassing. Indeed, this is not a classical usage of the
+parser, and Will didn't imagine that we may have used (and even documented)
+such a crude usage of FleXML. So, we now have to repare the bypassing
+functionnality to use the lastest FleXML version and fix the memory usage in
+SimGrid.
+
+\subsubsection faq_trouble_gras_transport GRAS spits networking error messages
+
+Gras, on real platforms, naturally use regular sockets to communicate. They
+are deeply hiden in the gras abstraction, but when things go wrong, you may
+get some weird error messages. Here are some example, with the probable
+reason:
+
+ - <b>Transport endpoint is not connected</b>: several processes try to open
+ a server socket on the same port number of the same machine. This is
+ naturally bad and each process should pick its own port number for this.\n
+ Maybe, you just have some processes remaining from a previous experiment
+ on your machine.\n
+ Killing them may help, but again if you kill -KILL them, you'll have to
+ wait for a while: they didn't close there sockets properly and the system
+ needs a while to notice that this port is free again.
+
+ - <b>Socket closed by remote side</b>: if the remote process is not
+ supposed to close the socket at this point, it may be dead.
+
+ - <b>Connection reset by peer</b>: I found this on internet about this
+ error. I think it's what's happening here, too:\n
+ <i>This basically means that a network error occurred while the client was
+ receiving data from the server. But what is really happening is that the
+ server actually accepts the connection, processes the request, and sends
+ a reply to the client. However, when the server closes the socket, the
+ client believes that the connection has been terminated abnormally
+ because the socket implementation sends a TCP reset segment telling the
+ client to throw away the data and report an error.\n
+ Sometimes, this problem is caused by not properly closing the
+ input/output streams and the socket connection. Make sure you close the
+ input/output streams and socket connection properly. If everything is
+ closed properly, however, and the problem persists, you can work around
+ it by adding a one-second sleep before closing the streams and the
+ socket. This technique, however, is not reliable and may not work on all
+ systems.</i>\n
+ Since GRAS sockets are closed properly (repeat after me: there is no bug
+ in GRAS), it is either that you are closing your sockets on server side
+ before the client get a chance to read them (use gras_os_sleep() to delay
+ the server), or the server died awfully before the client got the data.
+
+\subsubsection faq_trouble_errors_big_fat_warning I'm told that my XML files are too old.
+
+We have decided to change the units in SimGrid. Now we use Bytes, Flops and
+seconds instead of MBytes, MFlops and seconds... Units should be updated
+accordingly and the version of platform_description should be set to a
+valuer greater than 1:
+\verbatim
+ <platform_description version="1">
+\endverbatim
+You should try to use the surfxml_update.pl script that can be found
+<a href="http://gforge.inria.fr/plugins/scmcvs/cvsweb.php/contrib/platform_generation/?cvsroot=cvsroot%2Fsimgrid">here</a>.
+
+\subsection faq_trouble_valgrind Valgrind-related issues
+
+If you don't, you really should use valgrind to debug your code, it's
+almost magic.