How do I debug C++0x programs in MacPorts gcc 4.5?

Question

I have a simple c++ program I am trying to debug, but gdb cannot find the object file for the libraries (or no debug info is available), and it does not seem able to find th

Answer 1

Unlike other UNIXen, on MacOS the debug info is not linked into the executable. Instead, the executable has a list of object files which were linked into it, and the debugger looks for debug info in these individual object files.

If you remove the object files, then you can't debug.

When you compile and link the executable in "single step", GCC does this:

1. Create assembly file /tmp/[random-string].s
2. Assemble it into /tmp/[random-string].o
3. Link /tmp/[random-string].o with crt0.o, libc, etc. into mcmc executable.
4. Remove /tmp/[random-string].o and .s

It is that last step which prevents you from debugging.

Solution:

g++-mp-4.5 -Wall -pedantic -std=c++0x -g -ggdb -c MCMC-simplex.cpp
g++-mp-4.5 MCMC-simplex.o -lgsl -static-libstdc++ -o mcmc

This will leave MCMC-simplex.o in the current directory, and will allow GDB to find debug info in it.