Re: How to setup a breakpoint on constructor

Roland Zerek
2004-07-16T11:11:20Z

Użytkownik Michael Elizabeth Chastain napisał:

> See the PROBLEMS file:
>
> gdb/1091: Constructor breakpoints ignored
> gdb/1193: g++ 3.3 creates multiple constructors: gdb 5.3 can't set breakpoints

Well, I am using gdb-6.0 and gcc-3.4.0. Seems that problems remain...

> When gcc 3.x compiles a C++ constructor or C++ destructor, it generates
> 2 or 3 different versions of the object code. These versions have
> unique mangled names (they have to, in order for linking to work), but
> they have identical source code names, which leads to a great deal of
> confusion. Specifically, if you set a breakpoint in a constructor or a
> destructor, gdb will put a breakpoint in one of the versions, but your
> program may execute the other version. This makes it impossible to set
> breakpoints reliably in constructors or destructors [...]

However this is logical to have mangled names. And of course few
constructors. Even ISO says that the default constructor may be created by
the compiler in some situations...

> Things you can try:
>
> . modify your program so that the constructors that you want to
> breakpoint call some function that is not a constructor, and break
> on that.

I've already been considerring it.

> . run 'nm a.out | c++filt' to find the symbols in your program.
> break on the absolute address: "break *0x01234567". this is
> very crude (1960's technique) but it does work.

Seems nice. However my MinGW (Win XP) seems not to have these. I will take
a look of it later :-)

> . use nm, c++filt, and 'strip -N' to strip out symbols for
> not-in-charge constructors. This is scriptable, if someone
> wants to write a little script.

What the "not-in-charge" means?

Thx for reply.

--
Roland
r o l a n d z (at) poczta fm