gcov not showing any coverage data

Question

I am trying to use gcov on Linux(Ubuntu) to see frequency of execution for each line of source.

I have added following flags to my gcc compiler and linker flags,

CCFLAGS =  -fprofile-arcs -ftest-coverage
LDFLAGS = -fprofile-arcs -lgcov

but after compiling and running the program, i see no *.gcda file created. As a result of which when i run

gcov  --object-directory <path to the *.gcno/*.gcda files> myfile.cpp 

Shows error:

myfile.gcda:cannot open data file, assuming not executed
File '../../../../../code/myfile.cpp'
Lines executed:0.00% of 2625

Am i missing something. How to fix this?

Answer 1

You can use __gcov_flush() method inside your code. You will need to invoke this from registered signal handler.

See:

https://www.osadl.org/fileadmin/dam/interface/docbook/howtos/coverage.pdf

Using this, you can keep your service running and issue "kill" whenever you need to dump coverage data.

Hope that helps....

Answer 2

make sure the gcov and gcc are of the same version :), this where many of the people fail to check.

$gcc --version
gcc (GCC) 4.1.1
Copyright (C) 2006 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ find  /usr/lib/gcc -name libgcov.a
/usr/lib/gcc/x86_64-redhat-linux/4.1.1/32/libgcov.a
/usr/lib/gcc/x86_64-redhat-linux/4.1.1/libgcov.a
/usr/lib/gcc/x86_64-redhat-linux/3.4.6/32/libgcov.a
/usr/lib/gcc/x86_64-redhat-linux/3.4.6/libgcov.a

so the gcc version you have loaded should be atleast in the available list of libgcov.a