Re: Programmatic access to stack traces in C or C++ programs

[Michael Snyder <Michael dot Snyder at palmsource dot com>]

On Thu, 2006-10-19 at 22:27 -0400, Ashwin Bharambe wrote:
> Hi all,
> 
> I wanted to create a "stacktrace library" which would provide a
> routine to obtain the stacktrace of the program from any point
> _programmatically_ (like Java's stacktraces, for example..)

Can't be done in C (at least not without major hackery) -- 
you would have to write in assembler.

> I was aware of libc's non-standard stacktrace API but it did not quite
> work in many cases failing to resolve addresses, etc. It seems like
> stacktrace functionality is quite implementation and
> architecture-dependent.

Whatever you do would absolutely be architecture-dependent, and 
ABI dependent (as it is in gdb).


>  So, I was wondering if I could use portions of
> gdb's code to create such a library. Currently, to print a stacktrace,
> I utilize a piece of code (not mine, it's off the net) which fork()s a
> gdb sub-process, makes it ptrace the parent and run the command
> "backtrace". However this is quite time-consuming and sort of ugly.

That would surely work - but as you say, it is sort of ugly.

> My question, therefore, is: are there pieces of the code I can steal
> from libgdb to make this happen programmatically. I tried some naive
> ways of performing gdb_init() and then having it execute the
> 'backtrace' command (by invoking backtrace_command directly, for
> example), however gdb says there's no stack. This seems to be the case
> because it does not initialize its data structures without starting a
> process.

I think that's pretty hopeless.  But why don't you do it the easy way?

Just launch your program under gdb from the start, then use gdb
to put breakpoints at all the functions you are interested in.
You could write a script for that part.  Then, at each breakpoint, 
have gdb do this:

	silent
	backtrace
	continue

Voila, you've got all your backtraces.  And no overhead for forking.