Re: [Xenomai-help] gdb and heaps

[Philippe Gerum <rpm@xenomai.org>]

Alessandro Pittaluga wrote:
> Hi,
> 
> When trying to access with gdb to variables allocated on a shared heap,
> the following message is returned:
> (gdb) print mypointer
> $5 = (MYTYPE *) 0xb7dc4020
> (gdb) print *mypointer
> Cannot access memory at address 0xb7dc4020
> 
> All the applications (kernel and userland) are accessing correctly to
> the  heap-allocated memory. 
> 
> Is this the expected behaviour or there's something wrong in my
> installation?
>

Your installation is correct, GDB and Xenomai are too; unfortunately, 
the following explanation is still accurate, i.e. a restriction in the 
ptrace support:
http://sourceware.redhat.com/ml/gdb/2004-01/msg00152.html

Since you can call routines inside your program from the GDB cli, the 
best solution at hand would be to implement the suggestion found in this 
post: e.g.

void print_heap (void)
{
	... output the heap contents...
}

and,

(gdb) call print_heap()

You could even pass arguments to print_heap() for customizing your output.

A possible option to work around that would be to stop having heaps 
marked as I/O regions though, but the kernel-provided remapping helper 
we use currently forces this property. I'll look at this when time allows.

> Many Thanks
> Alessandro


-- 

Philippe.