Help with -finstrument-functions

[<thulasidhar at soc-soft dot com>]

Hi,
I am facing a strange problem when I tried to profile the call trace of my application using -finstrument-functions switch in gcc.

We have our application built as a shared library and we use python scripting language to test all the interfaces provided by this shared library.
It is the call trace of this shared library that I want to print.

When I create an executable by linking this shared library to a main.o (as follows), I get the call trace.
$ gcc main.o libtest_app.so -o app
$ app

This main.o contains only a main function that calls one of the interfaces present in libtest_app.so.

But when I import this shared library (libtest_app.so) into python, I do not get the call trace.

I analyzed the scenario in detail and these are my observations.
I have defined the functions __cyg_profile_func_enter and __cyg_profile_func_exit in my application, and I can see them in nm output.

$ nm libtest_app.so | grep __cyg
00177518 T __cyg_profile_func_enter
001775c4 T __cyg_profile_func_exit

Case 1: When I debug my application, built as an exe (app) I see that whenever it enters any function, it jumps to these above defined functions in libtest_app.so

Case 2: But when I debug my application, imported as an module in python, I see that whenever it enters any function it jumps to some symbol of the same name (__cyg_profile_func_enter) in glibc (source filename is displayed as noophooks.c).

The library is the same in both cases. What I don't understand is that if the shared library is built and linked, why should a reference to one function (__cyg_profile_func_enter) result in different jumps in different situations. Ideally all jumps to __cyg_profile_func_enter should have been resolved to refer to the symbol defined in my library, when I build the shared library (as follows),
$ gcc -shared -L/usr/lib/python2.2/config -lpython2.2 -o test/lib/libtest_app.so -lapp.a -lpthread -lrt -lm -ldl -lutil

Why doesn't this happen in the second case? Am I missing something here?

GCC version 3.3.1


Warm regards,
Thulasidhar J.K?






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