Question

When using GDB (using text interface, TTY, and SSH on Gentoo Linux) for debugging C code, I want to print the data in objects. When I try using print-object <objectname>, I get the message

evaluation of this expression requires the program to have a function “_NSPrintForDebugger”

I can’t find any documentation or examples (is it me, or is Linux documentation very short on examples?) of how to create such a function. I would like an example(s) of NSPrintForDebugger functions for gdb that I can model. Note that I am new to C, Linux, MPI, emacs, and gdb.

To make this a little more difficult, I can’t find the definition of all the objects I want to print.

If it helps make an example, some of the objects I’d like to print-object are:

1. UserData

   typedef struct {
   realtype dx, hdcoef, hacoef;
   int npes, my_pe
   MPI_Comm comm;
   realtype z[100];
   } *UserData;
   UserData data;

2. N_Vector (part of SUNDIALS, may have varying definitions).

3. void *cvode_mem (any pointer to void)
4. realtype (floats of varying size, also part of SUNDIALS)
5. MPI_Comm (which might be just an integer)

P.S. I have noticed that, for instance, p *data displays a lot of information. But I want more.

Answer 1

The NSPrintForDebugger function that the GDB print-object command is calling is part of the Objective-C runtime. Since you aren’t using Objective-C, ignore it.