Can GDB debug C++ lambdas?

Question

I use C++ 11 features actively. I have program created in Visual Studio 2013 that relies on lambdas to run multiple threads (lambda represents task, and thread receives lambda i

Answer 1

I've seen them in stack traces before, so it does at least know about them. I've never tried setting a normal breakpoint in one. It's sort of a hack, but you can set a breakpoint in one (or anywhere) by using asm volatile("int $3"); on x86(-64).

Here's an example program:

int main(){
    auto f = [](){
        asm volatile("int $3");
    };
    f();
    return 0;
}

Here's it's backtrace when it hits that breakpoint:

#0  0x0000000000400577 in main::{lambda()#1}::operator()() const ()
#1  0x000000000040058d in main ()

Answer 2

Step into Lamba's .run() go next/step (jump initializations) until the following call:

std::forward<>(args)(...)

Step into this one. It will lead you to you lambda body code.

Answer 3

From my experience, gdb cannot step into lambdas -- it just skips over them. Not only that, stepping into a lambda definition seems to confuse gdb and it proceeds to the end of the current function. You can, however, place a breakpoint explicitly inside a lambda, and if you hit that point, you will stop. This is obviously far from ideal.