HP gnu source-level debugger 5992-4701 manual Breakpoint menus

You can use breakpoint commands to start your program up again. Simply use the continue command, or step, or any other command that resumes execution.

Any other commands in the command list, after a command that resumes execution, are ignored. This is because any time you resume execution (even with a simple next or step), you may encounter another breakpoint―which could have its own command list, leading to ambiguities about which list to execute.

If the first command you specify in a command list is silent, the usual message about stopping at a breakpoint is not printed. This may be desirable for breakpoints that are to print a specific message and then continue. If none of the remaining commands print anything, you see no sign that the breakpoint was reached. silent is meaningful only at the beginning of a breakpoint command list.

The commands echo, output, and printf allow you to print precisely controlled output, and are often useful in silent breakpoints. See “Commands for controlled output” (page 290).

For example, here is how you could use breakpoint commands to print the value of

xat entry to foo whenever x is positive.

break foo if x>0 commands silent

printf "x is %d\n",x cont

end

One application for breakpoint commands is to compensate for one bug so you can test for another. Put a breakpoint just after the erroneous line of code, give it a condition to detect the case in which something erroneous has been done, and give it commands to assign correct values to any variables that need them. End with the continue command so that your program does not stop, and start with the silent command so that no output is produced. Here is an example:

break 403 commands silent

set x = y + 4 cont

end

5.1.7 Breakpoint menus

Some programming languages (notably C++) permit a single function name to be defined several times, for application in different contexts. This is called overloading. When a function name is overloaded, 'break function' is not enough to tell GDB where you want a breakpoint. If you realize this is a problem, you can use something like 'break function(types)' to specify which particular version of the function you want. Otherwise, GDB offers you a menu of numbered choices for different possible breakpoints, and waits for your selection with the prompt '>'. The first two options are

62 Stopping and Continuing