如何在C静态函数上设置VxWorks断点？

Question

I work on a vxworks platform in C. I am not able to set a breakpoint on a static C function. In fact when I do a lkup on the function name when the code is loaded on my card it is not found.

If I use nm and grep to find the symbol in the executable it looks exactly like the name of the function. We are porting code to our platform which uses (correctly) the static keyword for a large number of functions but it's a pain that I can't set a breakpoint on any of these.

Does any one know why I can't see the C static functions on lkup and how to look them up and set the breakpoint.

Thanks,

Rob

Answer 1

Assuming the routine really exists as you'd expect (ie, not optimized away or inlined) - I've used a couple approaches in situations like this:

Assembly breakpoint

• let's say you want to set a breakpoint at static function foo() . Find code that calls foo() - let's say bar() calls foo() . Where bar() calls foo() , set a breakpoint.

• run until you hit the breakpoint where bar() calls foo() . step at the assembly level. This should put you at the first instruction of foo() . Note that you might have to step through a few instructions if there are parameters being passed - hopefully you know what a branch / subroutine call looks like in your architecture.

• Set an assembly breakpoint when you land at the first instruction of foo() .

Function pointer

I've also worked around this by initializing a function pointer with foo() 's address. When system is running, read the function pointer in the debugger. Get foo() 's address. Set breakpoint based on this address.

Note that in these cases you might not have interleaved source, though.

Answer 2

I don't think it is possible to do what you want. The compiler is not required to generate symbols for static functions, it may even inline them.

Example:

$ gcc -o test test.c
$ nm test | grep foo
0000000000400524 t foo
$ gcc -O2 -o test test.c
$ nm test | grep foo
$

Answer 3

From the sound of it, you are using the shell to do your debugging and setting breakpoints.
If that's the case, you might have an issue since a static function has internal linkage and is no longer a globally visible function (to the shell).

If you are using DKMs and using the ld command to load the modules, you can add a parameter to LD that will also include static symbols which you should then be able to manipulate in the shell.