Debugging with GDB (September 2007)

180 Debugging with GDB
includes the steplast command, which helps to step into a function, and not into the
calls for evaluating the arguments. However, the steplast command is not available
on Integrity systems. The following example illustrates how GDB b e have s when you
execute the steplast command:
(gdb) 16 foo (bar ()); ---> bar() will return 10 (gdb) steplast foo (x=10) at
foo.c:4 4 int k = 10;
If the steplast command is not meaningful for the current line, GDB displays the
following error message:
"Steplast is not meaningful for the current line."
For example,
(gdb) 4 int k = 10; (gdb) sl ---> alias to "steplast" command error: Steplast
is not meaningful for the current line
To execute the steplast command in C++ compiled applications, you must compile
the application using the HP aC++ version A.03.50 or later with the -g0 option.
In C++, the steplast command is helpful while debugging heavy templated functions,
because it directly steps into the call, thus skipping the constructor calls, if any. This
behavior is unlike the step command that steps into the constructor itself.
Consider the following example:
void call_me ( string s ) ... (gdb)
10
call_me ( "hello" );
(gdb) steplast call_me (s=static npos = 4294967295,
static nullref = ref_hdr = mutex_= dummy1 = 0x7f4f79e0, dummy2 = 2136325568,
refs_ = 2136327612,
capacity_ = 2136327468, nchars_ = 2136327464, eos_char = 64 ’@’,
alloc_ = <No data fields>,
value_allocator = alloc_ = 0x7f7f133c,
data_ = 0x40003a64 "hello") at str.C:55
printf ("Will just print the value of \n");
If there are multiple top-level calls, the steplast command enables you to step into
each top-level call. For example, for the following line, the steplast command takes
you to the first top-level call, (foo()):
foo(bar()) + bar(foo());
Debug foo(), use the finish command to exit from the first top-level call, (foo()),
execute the steplast command to step into the next top-level call, (bar()). The
following example illustrates the use of steplast command:
(gdb)10 foo( bar() ) + bar( foo() ) (gdb) sl Use the steplast (sl) command to
step
14.24 Ge tting information from a non-debug executable
You can get some information about the arguments passed to the functions displayed
in the stack trace in a non-debug, optimized executable.