Is it possible code coverage of a shared library using gcov? - opencv

Question

I try to test an executable which uses OpenCV shared library. When using gcov to know what code lines were covered I only get info about my .cpp files and .hpp of the library. No info is shown about .cpp files of the library.
I compiled and linked with -pg --coverage flags.

Answer 1

Yes, gcov can give coverage information about a shared library. If I remember correctly from the problems I had getting this to work on my project, you're probably not including the --coverage flag on the linking of the dynamic library. Here's the smallest example I could create.
Makefile:
CXXFLAGS += --coverage
LDFLAGS += --coverage
myexec: myexec.cpp libmylib.so
libmylib.so: mylib.o
gcc --coverage -shared -Wl,-soname,libmylib.so -o libmylib.so mylib.o
mylib.o: CXXFLAGS += -fPIC
myexec.cpp:
#include "mylib.h"
int main(int argc, char** argv)
{
return is_even(argc);
}
mylib.h
#ifndef MYLIB_H
#define MYLIB_H
int is_even(int num);
#endif
mylib.cpp
#include "mylib.h"
int is_even(int num)
{
if (num % 2)
return false;
else
return true;
}
Output of make (so you can see exactly what the build was):
g++ --coverage -fPIC -c -o mylib.o mylib.cpp
gcc --coverage -shared -Wl,-soname,libmylib.so -o libmylib.so mylib.o
g++ --coverage --coverage myexec.cpp libmylib.so -o myexec
I ran the executable using LD_LIBRARY_PATH="." ./myexec a, and then ran gcov mylib.cpp. Here's the contents of mylib.cpp.gcov:
-: 0:Source:mylib.cpp
-: 0:Graph:mylib.gcno
-: 0:Data:mylib.gcda
-: 0:Runs:1
-: 0:Programs:1
-: 1:#include "mylib.h"
-: 2:
1: 3:int is_even(int num)
-: 4:{
1: 5: if (num % 2)
#####: 6: return false;
-: 7: else
1: 8: return true;
-: 9:}