Using third-party libraries

[ben.boeckel (Ben Boeckel (Kitware))]

@Saviz

target_include_directories()

# Specifies the directories that have header files in them. It will add those directories with their header files to the target.

This looks fine.

@Saviz

target_link_libraries()

# Links the library files to the final executable, so it can work after being exported.

This is correct, but not a complete picture. tll works by applying usage requirements of targets (the “right hand side”) to other targets (the “left hand side”). So target_link_libraries(tgt PRIVATE foo) says “give tgt the usage requirements of foo, but not those using tgt”. Usage requirements can be things like compile definitions, include directories, compile options, link options, libraries to link, and a few more.

@Saviz

find_package()

# Find a package and load its package-specific details

Pretty much correct. Note that what it means to “find” a specific package can vary greatly.

@Saviz

find_library()

# This command is used to find a library

If by “find” you mean “find where a library lives on the system”, yes. It has nothing to do with the linker finding said library though.

@Saviz

If “target_include_directories” locates the header files (.h files) and “target_link_libraries” identifies and links the necessary libraries to the final executable (.cpp and *.lib files), then the question arises: what purpose does “find_package” serve? (Aren’t header files and their corresponding implementation libraries all that’s required to utilize a library?)

Here I see some confusion. target_include_directories(tgt) does not “locate” anything. It just says “tell the compiler when to add these directories to the include search path when compiling tgt”. This is basically a set of -I flags pretty much everywhere.

There are two parts:

• finding where things are on the system
• using them for specific things

So the find_* commands all handle the first part. But they do nothing about actually using this information. That belongs to the target_* family of commands.

@Saviz

What sets apart “find_package” from “find_library”? (Both appear to serve the purpose of locating a library, yet one is labeled as a “package” and the other as a “library.” What advantages and disadvantages do they each bring to the table?)

A package is a logical collection of artifacts (headers, libraries, resources, executables, whatever). find_library is about finding a specific library.