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Original commit message from CVS: added all of my un-committed random doc files, as backup <g>
30 lines
2.2 KiB
Text
30 lines
2.2 KiB
Text
Changes made to the DEBUG system. New header file gstdebug.h holds the stuff to keep it out of gst.h's
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hair. DEBUG prints out the process id, cothread id, source filename and line number. Two new macros
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DEBUG_ENTER and DEBUG_LEAVE are used to show the entry and exit of a given function. This eventually
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might be used to construct call trace graphs, even taking cothreads into account. This would be quite
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useful in visualizing the scheduling mechanism.
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Minor changes to various debug messages.
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Also sitting in gstdebug.h is a prototypical DEBUG_ENTER that's capable of performing DEBUG_LEAVE
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automatically. It does this by utilizing a little-known GCC extension that allows one to call a
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function with the same parameters as the current function. The macro uses this to basically call
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itself. A boolean is used to ensure that when it calls itself it actually runs the body of the
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function. In the meantime it prints stuff out before and after the real function, as well as
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constructing a debugging string. This can be used eventually to provide call-wide data on the DEBUG
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lines, instead of having to replicate data on each call to DEBUG. More research is needed into how this
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would most cleanly be fit into some other chunk of code, like GStreamer (I think of this DEBUG trick as
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a separate project, sorta).
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Unfortunately, the aforementioned DEBUG trick interacts quite poorly with cothreads. Almost any time
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it's used in a function that has anything remotely to do with a cothread context (as in, it runs in
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one), a segfault results from the __builtin_apply call, which is the heart of the whole thing. If
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someone who really knows assembly could analyze the resulting code to see what's really going on, we
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might find a way to fix either the macro or the cothreads (I'm thinking that there's something we missed
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in constructing the cothreads themselves) so this works in all cases.
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In the meantime, please insert both DEBUG_ENTER and DEBUG_LEAVE in your functions. Be sure to put
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DEBUG_ENTER after your variable declarations and before any functional code, not to put the function
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name in any DEBUG strings (it's already there, trust me), and put a DEBUG_LEAVE if you care enough.
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Changes are going to happen in the way DEBUGs and other printouts occur, so stay tuned.
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