Read debugging information at runtime from an application

Question

I have some questions regarding debugging symbols and what can be done with them, besides, well, debugging. I'm mostly interested in answers regarding GCC, but I'd also be happy to know how it looks like under other compilers, including MSVC.

First of all:

• What are the common formats/types of debugging symbols?
• How do they relate to compilers and platforms? Is it always the same format on GCC and MinGW among platforms?
• Can I check in runtime whether the build has them and what format are they in?

And some more practical questions... How can I:

• Check the current file and line number?
• Obtain the (qualified) function name being executed?
• Obtain a full current stack trace?

Let me emphasize that I'm talking about run-time checks. All of those can be read and pretty-printed by GDB, but I don't know how much info comes from the debugging symbols themselves and how much from the source code which GDB also has access to.

Maybe there's a library which is able to parse the debugging symbols and yield such information?

Are the debugging symbols standardised well enough that I can expect some degree of portability for such solutions?

Answer 1

What are the common formats/types of debugging symbols?

DWARF and STABS (those are embedded inside executable, in special sections), Program Database (PDB; external file, used by MSVC).

How do they relate to compilers and platforms? Is it always the same format on GCC and MinGW among platforms?

GCC uses DWARF/STABS (I think it's a GCC compile-time option) both on Linux (ELF) and Windows (PE), don't know about others. MSVC always uses PDB.

Can I check in runtime whether the build has them and what format are they in?

You can parse the executable image and see if there are sections with debugging info (see STABS documentation and DWARF specs). PDB files are distributed either with executables or via symbol servers (so if you don't want to go online, check if there is X.pdb for X.exe/X.dll).

About how to read and use those symbols — I don't know about DWARF/STABS (there's probably something around GNU binutils that can locate and extract those), but for PDB your best bet is to use dbghelp — its usage is pretty well documented and there are a lot of examples available on the net. There's also DIA SDK that can be used to query PDB files.

Are the debugging symbols standardised well enough that I can expect some degree of portability for such solutions?

DWARF has a formal specification, and it's complicated as hell. PDB AFAIK is not documented, but dbghelp/DIA are, and are the recommended way.