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Re: gdb 6.3 C++ breakpoint in constructor/destructor patch


Hello,

On Sun, 1 May 2005 15:05:32 -0400, Daniel Jacobowitz <drow@false.org> wrote:

On Sun, May 01, 2005 at 08:32:12PM +0200, Thomas Maier wrote:
Hello,

I want to supply a patch for the released gdb 6.3, that fixes partially
the gdb bugs

gdb/1091: Constructor breakpoints ignored
gdb/1193: g++ 3.3 creates multiple constructors: gdb 5.3 can't set
breakpoints

I was really confused, why my programs to not stop at the breakpoint in
constructor/destructors. Now i know, it is not the fault of my programs ;)
Since this anoying problem seems to be in gdb since the gcc 3.x release, i
guess, no one else a) has this problem (i don't believe so) or b) will not
fix it. So i did it ;)


This modification is only made for commands like "break
[source]:<lineno>". For C++ constructors and destructors, the patch
creates more than one breakpoint at the source at lineno, but each
generated breakpoint will have another address!

NOTE: this is only a simple "hack". I have spent only one day to get into
gdb source code and do the modification.
It would be better, to create only one breakpoint in such C++ constructors
and destructors and assign multiple addresses to it. But this needs a huge
modification of gdb, i guess ;)

This is not a very useful change, because it only handles the case where everything at a particular line is in the same symtab. Often this will not be the case.

Ok, hmm, then the code in find_line_symtab() must not return one symtab, which is used to find one or more references to the lineno, it must return a list of symtabs with references to this lineno. Means, a similar search over all symtabs which is already done in find_line_symtab(). Would that be enough to handle the file:lineno case?

(If yes it think a new function like find_multi_line_symtab() is the best
way to do it, then in decode_all_digits() fill in the sals with the found
symtabs + linenos)

If you take a look at the archives for the list, you will find a lot of
discussion on this subject - as well as a prototype patch I posted
earlier this year.  That patch may be good enough for your needs, since
it handles the file:lineno case.  But it isn't done yet, and I haven't
had time to go back to it yet.


Intresting...



-Thomas Maier




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