[Bug gcov-profile/96919] [GCOV] uncovered line of stack allocation while using virutal destructor

["libin.dang at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96919

--- Comment #6 from Libin Dang <libin.dang at gmail dot com> ---
(In reply to Martin Liška from comment #2)
> Using latest GCC release you can see what happens:
> 
> $ g++ pr96919.cc --coverage && ./a.out && gcov a-pr96919.cc -t
> hello
> libgcov profiling
> error:/home/marxin/Programming/testcases/a-pr96919.gcda:overwriting an
> existing profile data with a different timestamp
>         -:    0:Source:pr96919.cc
>         -:    0:Graph:a-pr96919.gcno
>         -:    0:Data:a-pr96919.gcda
>         -:    0:Runs:1
>         -:    1:class Base {
>         -:    2:public:
>         -:    3:  Base() = default;
>        1*:    4:  virtual ~Base() = default;
> ------------------
> _ZN4BaseD0Ev:
>     #####:    4:  virtual ~Base() = default;
> ------------------
> _ZN4BaseD2Ev:
>         1:    4:  virtual ~Base() = default;
> ------------------
>         -:    5:  virtual void foo() = 0;
>         -:    6:};
>         -:    7:class Hello : public Base {
>         -:    8:public:
>         -:    9:  Hello() = default;
>        1*:   10:  ~Hello() = default;
> ------------------
> _ZN5HelloD0Ev:
>     #####:   10:  ~Hello() = default;
> ------------------
> _ZN5HelloD2Ev:
>         1:   10:  ~Hello() = default;
> ------------------
>         -:   11:  void foo() override;
>         -:   12:};
>         -:   13:
>         -:   14:#include <iostream>
>         -:   15:
>         -:   16:using namespace std;
>         -:   17:
>         1:   18:void Hello::foo() {
>         1:   19:  cout << "hello" << endl;
>         1:   20:}
>         -:   21:
>         1:   22:int main(int argc, char* argv[]) {
>     #####:   23:  Hello hello;
>         1:   24:  hello.foo();
>         1:   25:  return 0;
>         -:   26:}
> 
> So yes, it's a virtual destructor _ZN4BaseD0Ev that is not called.
> And the not executed line:
>     #####:    4:  Hello hello;
> 
> corresponds to a basic block 
> 
>   <bb 5> :
> <L3>:
>   Hello::~Hello (&hello);
>   resx 2
> 
> which would be executed when the Hellow constructor fails.

A strange thing about this test case:

If I removed 'return 0;' at line 25, gcov will mark line 23 as executed.


Tested with both gcov 8.3 and 10.2.