windows gdb.exe, setting breakpoints before debugging cause extremely slow loading

asmwarrior asmwarrior@gmail.com
Thu Jul 22 00:34:00 GMT 2010


  On 3:59, asmwarrior wrote:
>  Hi, all, I'm a windows gdb user, I have used both official MinGW 
> gdb.exe and gdb.exe build myself.
>
> I found that when I set a breakpoint before loading or after loading 
> has much different result.
> I use GDB.exe under Codeblocks, here is the debugger log when I try to 
> debug something:
> ---------------------------------------------------------------------------- 
>
> Situation works badly:
>
> I just set breakpoint before I start "run" the debugee
>
> >>>>>>cb_gdb:
> > break 
> "E:/code/cb/cc_branch/src/plugins/codecompletion/parser/parserthread.cpp:471"
> No source file named 
> E:/code/cb/cc_branch/src/plugins/codecompletion/parser/parserthread.cpp.
> Breakpoint 1 
> ("E:/code/cb/cc_branch/src/plugins/codecompletion/parser/parserthread.cpp:471) 
> pending.
> >>>>>>cb_gdb:
> > run
>
> Now, it will take about 1 and a half minutes to start the debugee.
>
> ---------------------------------------------------------------------------- 
>
> But If I do *not* set any breakpoint before running, then ,the loading 
> stage is quite fast(about 10 second), after that I can still set 
> breakpoint and all the breakpoint works fine.
>
> Not only me find the problem, see the message posted in Codeblocks 
> forum by One of Codeblocks developers Pecan:
> http://forums.codeblocks.org/index.php/topic,12951.msg87332.html#msg87332
>
> Does this a gdb bug?
>
> Thanks
>
> asmwarrior(ollydbg from codeblocks forum)
>


I personally think there is something wrong with "pending breakpoint" 
when we load a shared dll library.

As my initial guess, When after loading some new shared libraries, gdb 
need to check if the pending breakpoint can be set to the new libraries. 
if Yes, then the these breakpoint can translated from "pending 
breakpoint" to "real breakpoint".

return to my problem:
I guess there are some recursive search algorithm for pending 
breakpoints after some new shared library debug information is loaded.

Can some one give me a direction that how does gdb treat with "pending 
breakpoint" after loading some new shared libraries?
I have read the gdb source "breakpoint.c" there:

struct breakpoint *b

if b->loc is NULL, which means it is a pending breakpoint. So, where and 
when will be this pointer member filled.

Thanks

asmwarrior






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