Conditions under which stepping into shared library should work in gdb?

Question

There are many questions related to specific errors why stepping into a shared library with gdb isn\'t working. None of them provide a systematic answer on how to confirm wh

Answer 1

Some more tests you can do on built shared library:

1. file libmyshared-ggdb.so should report that library has debug info and not stripped.
2. nm libmyshared-ggdb.so | grep print_from_lib should find the symbol for print_from_lib function.

If all above tests passed try to load the library directly in gdb and find the function:

gdb libmyshared-ggdb.so
(gdb) info functions print_from_lib

Function print_from_lib name should be printed. If not, something is wrong with gdb or gcc.

Answer 2

GDB 7.11 can't reproduce this problem. This is my steps. I hope this will help you:

1.gcc -ggdb -c -Wall -Werror -fpic myshared.c -o myshared-ggdb.o
2.gcc -ggdb -shared -o libmyshared-ggdb.so myshared-ggdb.o
3.gcc -ggdb main.c -lmyshared-ggdb -o app-ggdb -L.
4.gdb ./app-ggdb

In GDB,

(gdb) set env LD_LIBRARY_PATH=.
(gdb) b main.c:7
Breakpoint 1 at 0x4006a5: file main.c, line 7.
(gdb) r
Starting program: /home/haolee/tmp/app-ggdb 

Breakpoint 1, main () at main.c:7
7       print_from_lib();
(gdb) s
print_from_lib () at myshared.c:5
5       printf("Printed from shared library\n");
(gdb) 

I step into the function print_from_lib successfully.

Answer 3

Your problem is self-imposed: don't do this: set step-mode on, and step will work as you expect.

From the GDB manual:

set step-mode
set step-mode on
The set step-mode on command causes the step command to stop at the first
instruction of a function which contains no debug line information
rather than stepping over it.

This is useful in cases where you may be interested in inspecting the machine
instructions of a function which has no symbolic info and do not want
GDB to automatically skip over this function.

You are interested in the opposite of the above -- you want to step into the print_from_lib function and avoid stopping inside the PLT jump stub and the dynamic loader's symbol resolution function.