breakpoint

You can change the source code while the program is paused in the debugger, for instance in a breakpoint, and continue after your modifications.

You first have to localize a region (function) you want to study, then you reach one of its execution with a breakpoint, or a conditional breakpoint.

Brendan answered with advantages, but for how: it's still just a software breakpoint, int3/0xCC on x86 as you say.

Just find a defun, eval it via C-u C-M-x and you'll get breakpoint at the defun entry.

Even when using C, you can use gdb to evaluate subexpressions at a breakpoint.

Typing in a method call on the line where you want to debug isn't much of a leap from clicking a breakpoint.

Just put the breakpoint on that line, then check the intermediate values (e.g.

So it boils down to: should I spend 5 minutes figuring out how to set this conditional, print-only breakpoint?

Usually, I find place where to put breakpoint by just searching keyword associated with my request; 5.

But the round trip of dealing with that breakpoint is much tighter, because the handler function is called directly in the kernel trap, without even a context switch.

Uprobes has about the minimal overhead that a software breakpoint can possibly have, whereas involving a userspace debugger requires a bunch of syscalls and context switches every time.

Not sure if you know this but if you're in javascript you can just drop a 'debugger;' statement anywhere in your code and it will function as a breakpoint.

Sounds like what you're describing is a situation where you have to modify your source code to add a breakpoint (similar to a "debugger" statement in JavaScript or C#).

I tended to put all the "static" data for a module within a structure, usually called "m", and would have the debugger do a "print m" and a "locals" automatically whenever it hit a breakpoint.