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12.5 Can GDB print class members?

Q: It seems that GDB doesn't recognize C++ class members by their original, unmangled names. Do I really need to figure out the mangled names of all my class variables and methods to be able to debug them?

A: No, you don't. GDB does allow you to use the original names, it's just that it usually treats the :: in their names as word delimiters. Include the name of the method or a class static variable in single quotes, and GDB will recognize them as a single word. For example, if your class CMPForward has a method named go which you need to put a breakpoint in, use the following command:

  breakpoint 'CMPForward::go'

Other GDB features that might be useful in this context are the various demangling options, like set print demangle, set demangle-style etc.; look them up in the GDB on-line docs.

However, there are some cases where you won't be able to get GDB to demangle C++ function names no matter how hard you try. This is due to a lack of sufficient debugging information in the COFF debug data format. There's simply not enough info there for GDB to detect the source language and support some C++-specific features. So, in some case, you will need to use mangled names. If you need a description of the GNU style of mangling C++ names (so you could mangle them yourself), look in the GDB or Libg++ source distribution, in the libiberty directory, for a file named cplus-demangle.c. You can also use the cxxfilt utility, supplied as part of the GNU Binutils package, to demangle the names and verify that your mangling is correct. Note that, as the debugger built into RHIDE uses GDB code, it will also sometimes have such problems with debugging C++ programs.

If you really need full C++ support in DJGPP, you will have to use the stabs debugging support. GCC 2.8.0 and later are distributed with built-in stabs support, so, if you need this, upgrade and compile your C++ programs with -gstabs+. Caveat emptor: FSDB, EDEBUG32 and SYMIFY don't understand the stabs format, so you will have to compile with -gcoff option to use these utilities (RHIDE distribution includes a utility called gsymify that can be used instead of SYMIFY with stabs debugging info).

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