gprof : How to generate call graph for functions in shared library that is linked to main program

Question

I am working on Linux environment. I have two 'C' source packages train and test_train.

1. train package when compiled generates libtrain.so
2. test_train links to libtrain.so and generates executable train-test

Now I want to generate a call graph using gprof which shows calling sequence of functions in main program as well as those inside libtrain.so

I am compiling and linking both packages with -pg option and debugging level is o0. After I do ./train-test , gmon.out is generated. Then I do:

$ gprof -q ./train-test gmon.out

Here, output shows call graph of functions in train-test but not in libtrain.so

What could be the problem ?

Answer 1

gprof won't work, you need to use sprof instead. I found these links helpful:

• How to use sprof?
• http://greg-n-blog.blogspot.com/2010/01/profiling-shared-library-on-linux-using.html

Summary from the 2nd link:

1. Compile your shared library (libmylib.so) in debug (-g) mode. No -pg.
2. export LD_PROFILE_OUTPUT=`pwd`
3. export LD_PROFILE=libmylib.so
4. rm -f $LD_PROFILE.profile
5. execute your program that loads libmylib.so
6. sprof PATH-TO-LIB/$LD_PROFILE $LD_PROFILE.profile -p >log
7. See the log.

I found that in step 2, it needs to be an existing directory -- otherwise you get a helpful warning. And in step 3, you might need to specify the library as libmylib.so.X (maybe even .X.Y, not sure) -- otherwise you get no warning whatsoever.