The Linux Programming Interface

842 Chapter 41

Figure 41-1 shows the compilation and linking steps involved in producing a shared

library with an embedded soname, linking a program against that shared library,

and creating the soname symbolic link needed to run the program.

Figure 41-1: Creating a shared library and linking a program against it

Figure 41-2 shows the steps that occur when the program created in Figure 41-1 is

loaded into memory in preparation for execution.

To find out which shared libraries a process is currently using, we can list the

contents of the corresponding Linux-specific /proc/PID/maps file (Section 48.5).

ELF header

(other info)

soname=libbar.so

(other info)

$ gcc -g -c \

-fPIC -Wall \

mod1.c mod2.c mod3.c

$ gcc -shared -o libfoo.so \

-Wl,-soname,libbar.so \

mod1.o mod2.o mod3.o

$ gcc -o prog \

prog.c libfoo.so

mod1.o code

mod1.o

libfoo.so

mod2.o code

mod2.o

mod3.o code

mod3.o

prog.o code

prog libbar.so

mod2.o code

$ ln -s libfoo.so \

libbar.so

mod1.o code

mod3.o code

Program header “libfoo.so”

Shared object dependencies:

/lib/ld-linux.so.2

libbar.so

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