Re: setfault calling functions within gdb

[Jim Blandy <jimb at redhat dot com>]

I don't see anything obviously wrong with what you're doing (although
someone is certain to pop up and correct me).  Could you file this as
a bug report at http://sources.redhat.com/gdb/bugs/, so it won't get
lost?

Faheem Mitha <faheem@email.unc.edu> writes:

> Dear People,
> 
> I'm having problems calling functions from within gdb. Can someone tell me
> what I am doing wrong? Consider the following innocuous program
> 
> ---------------------------------------------------------
> #include<vector>
> #include <iostream>
> 
> using std::vector;
> using std::cout;
> 
> typedef vector<double> Point;
> void print(Point pt);
> 
> int main()
> {
>   Point foo(3,1.0);
>   //print(foo);
> }
> 
> void print(Point pt)
> {
>   unsigned int i;
>   cout << "[";
>   for(i=0; i < pt.size(); i++)
>     {
>       cout << pt[i];
>       cout << ",";
>     }
>   cout << "]";
> }
> -----------------------------------------------------------
> 
> When I set a breakpoint after the definition of foo and call
> print(foo) I get a segfault. There appears to be nothing wrong with
> this function, since print(foo) when compiled into the function works
> as expected. Also, "print foo[0]" works fine. There seem to be two
> possibilities; a) I am doing something wrong, b) this is a bug in
> gdb. I'm hoping it is the former. I dimly recall calling functions
> successfully sometime in the past, but I can't remember whether it was
> in C or C++ code.
> 
> Any help would be greatly appreciated. This is really frustrating!
> Output from gdb follows. I'm using gdb, gcc-3.0 on Debian Sarge. The
> respective versions are
> 
> ii  gdb                   5.2.cvs20020401-6      The GNU Debugger
> ii  g++-3.0               3.0.4-9                The GNU C++ compiler.
> 
> I locally compiled the slightly more recent version of gdb from August
> which is in unstable, but I get the same behaviour.
> 
>                                               Faheem.
> 
> (gdb) call print(foo)
> [
> Program received signal SIGSEGV, Segmentation fault.
> 0x0804a1a4 in print(std::vector<double, std::allocator<double> >)
> (pt=0x804f008) at test.cc:22
> The program being debugged was signaled while in a function called
> >From GDB.
> GDB remains in the frame where the signal was received.
> To change this behavior use "set unwindonsignal on"
> Evaluation of the expression containing the function
> (print(std::vector<double, std::allocator<double> >)) will be
> abandoned.
> (gdb)