Question

I developed a simple example to test gcovr and gcov:

#include <iostream>                                                                                                                                       

int main (int argc, const char * argv[])                                                                                                                  
{                                                                                                                                                         
    std::cout << argc << std::endl;                                                                                                                       

    if(argc == 1)                                                                                                                                         
    {                                                                                                                                                     
        int y = 1;                                                                                                                                        
        std::cout << "Argc > 1" << std::endl;                                                                                                             
    }                                                                                                                                                     
    if(argc == 2) std::cout << "Argc > 2" << std::endl;                                                                                                   
    if(argc == 3)                                                                                                                                         
    {                                                                                                                                                     
        std::cout << "Argc > 3" << std::endl;                                                                                                             
    }                                                                                                                                                     

    int i = 34;                                                                                                                                           
    i = i * i;                                                                                                                                            

    return 0;                                                                                                                                             
}   

And a script for coverage report generation:

#! /bin/bash                                                                                                                                              

rm -rf build-run                                                                                                                                          
mkdir build-run                                                                                                                                           
cd build-run                                                                                                                                              

g++ -O6 -DDEBUG=0 --coverage -ftest-coverage -fprofile-arcs -c -o main.o ../main.cpp                                                                      

g++ -O6 -DDEBUG=0 --coverage -fprofile-arcs -ftest-coverage -lgcov -o coverage ./main.o                                                                   

./coverage > out                                                                                                                                          
./coverage --help > out                                                                                                                                   
./coverage --help --out > out                                                                                                                             

gcovr -v -kpbu -r .. -o ../branch-report.txt                                                                                                              
gcovr -v -kpu -r .. -o ../report.txt      

I got coverage 80% using -b option and it point me on the last line in main block. It seems to me that it should be 100% for such scenario or not?

Answer 1

This is an issue with gcov. If you look at the underlying gcov output [which the example driver is so courteous to leave for us as build-run/^#main.cpp.gcov], you see:

[…snip…]
        3:   21:    return 0;
function _Z41__static_initialization_and_destruction_0ii called 3 returned 100% blocks executed 100%
        6:   22:}
branch  0 taken 3 (fallthrough)
branch  1 taken 0
branch  2 taken 3 (fallthrough)
branch  3 taken 0
function _GLOBAL__I_main called 3 returned 100% blocks executed 100%
        3:   23:/*EOF*/
call    0 returned 3

I think what is being reported is branch coverage for the destructors of static members of objects in the iostream library. … while we try and filter out most of the gcov weirdness through gcovr, this is one of the cases that we cannot reliably ignore.

Bill Hart
John Siirola

P.S. I encourage you to submit gcovr tickets on the gcovr Trac page: https://software.sandia.gov/trac/fast/newticket