Will my gdb work when using templates?

Question

I plan to templatize a container class which can be used for various data types. I currently have a big concern:

Will my gdb still work in the template? Can I set breakpoints, print values, print stack traces, etc in a class template as in a normal member function?
Where are the limits? Are there serious restrictions or weird behavior to expect?

I'm not talking about debugging the template instantiation itself and I'm also not talking about extensive metaprogramming.

I did some research on the internet, but search results are full with real template debugging and it's hard to find an answer on this (hopefully) relatively simple question.

See also [c++ - GDB breakpoints do not hit template functions - Stack Overflow](https://stackoverflow.com/questions/61600798/gdb-breakpoints-do-not-hit-template-functions) — user202729, Mar 10 '22 at 03:32

Klaus · Answer 1 · 2014-07-10T13:10:26.997

3

You can break with gdb on all instances of a template with using the gdb rbreak command! That makes the usage much! easier.

#include <iostream>
#include <string>

template < typename T>
T Foo(T t) { return t; }

int main()
{
    std::cout << Foo<int>(1) << std::endl;
    std::cout << Foo<std::string>("Hallo") << std::endl;
}

You can use gdb as follows:

gdb> rbreak Foo<.*>
Breakpoint 4 at 0x400cc5: file main.cpp, line 5.
int Foo<int>(int);
Breakpoint 5 at 0x400cda: file main.cpp, line 5.
std::basic_string<char, std::char_traits<char>, std::allocator<char> > Foo<std::string>(std::string);

Hope this helps!

edited Jul 10 '14 at 13:10

answered Jul 10 '14 at 13:00

Klaus

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I do identical to this solution but get a `Function "_Z3FooIiET_S0_" not defined in "/tmp/a.cpp". Make breakpoint pending on future shared library load? (y or [n]) ` for some reason. – user202729 Mar 10 '22 at 03:33

score 2 · Accepted Answer · answered Jul 10 '14 at 12:50

Normal Class

class foo
{
private:
    int x;
public:
    foo(int n = 0):x(n) {cout<<"foo::foo(int)"<<endl;}
    ~foo() {cout<<"foo::~foo()"<<endl;}
};

To put the breakpoint, we follow as below
$gdb: b foo::foo(int)
      b foo::~foo()

=========================================================

Template class Example

template<typename T>
class bar
{
private:
    T x;
public:
    bar(T n = 0):x(n) {cout<<"bar::bar(int)"<<endl;}
    ~bar() {cout<<"bar::~bar()"<<endl;}
};

To put the breakpoint, we follow as below
$gdb: b bar<int>::bar(int)
      b foo<int>::~bar()

The only thing we need to understand is(which I guess confuted you), that when we debug template class, we can not use the break point like bar<T>::bar(). When program runs, program would instantiate the template class with a particular type as bar<int>::bar().

Apart from that, there is no difference while debugging the non-template vs template based class. Only thing we need to consider is, template bases class would be bit verbose and it takes some time to understand especially.

Will my gdb work when using templates?

2 Answers2