Gcc

GCC

Shared Libraries

Naming convention

Real Name

all libraries do not follow the convention

• lib.so.x.y.z (libjpeg.so.1.2.3)
• lb-x.yy.so (libc-2.31.so)

name -> name of the Library x -> major version number y -> minor version number z -> patch version number

Shared Object Name (soname)

• Label for a major version of a shared object
  • soname: libjpeg.so.1 => libjpeg.so.1.2.3
• helps to resolve shared library dependencies

Linker Name

• gcc will look for this during
• libname.so

To create a shared library

source code -> object file -> shared library

• gcc -fpic -c source.c
  • creates an object file source.o with position-independent code (PIC)
• gcc -fpic source1.o source2.o -shared -Wl,-soname,libjpeg.so.1 -o libjpeg.so.1.2.3
  • creates a shared library from the object file
• utilize the created shared library during compiling and linking
  • gcc main.c -L. -ljpeg -o main
    • -L. tells the linker to look in the current directory for libraries
    • -ljpeg tells the linker to link against libjpeg.so (the linker will resolve this to libjpeg.so.1.2.3 based on the soname)

LB_LiBRARY_PATH environment variable

• specifies a list of directories where the linker should look for shared libraries at runtime
• if the shared library is not found in the standard locations, the linker will search the directories

Shared object libraries (.so files) on Linux/Unix systems are primarily located in standard paths like /lib, /usr/lib, and /usr/local/lib. The dynamic linker (ld.so) searches these directories, along with paths defined in /etc/ld.so.conf and LD_LIBRARY_PATH`, to resolve library dependencies at runtime

Static Libraries

References:

• https://www.youtube.com/watch?v=UdMRcJwvWIY