haxpor / makefile_cpp_sample

Just a sample C++ built with Makefile to remind myself about target usage in Makefile

makefile_cpp_sample

Just a sample C++ built with Makefile to remind myself about target usage in Makefile

Project

Sample project used in this repository for Makefile demonstration has the following setup.

• library project built as shared library (.so) - util.cpp, and util.h
• main program which consumes such library - main.cpp

The project utilizes Makefile to build.

Makefile

It provides the following targets (not include internal targets although can be used, but not as part of concern for users)

• all - build both library, and main program (didn't execute a binary executable)
• lib - build library as shared library (.so)
• main - build main program as an executable binary
• clean - remove all artifact files
• test - to execute the executable binary (you might have to set LD_LIBRARY_PATH to current directory first externally via export LD_LIBRARY_PATH=$PWD)

Notice on Makefile

Key an eye on the Makefile's target, and .PHONY. They are related to each other.

Example hit-in-the-knee case - .PHONY

I've been hit with this case. If your Makefile produces an executable named main.out, and you also include this as part of .PHONY, then it's bad.

Makefile use .PHONY to differentiate between a target, and actual filename. Because Makefile itself is based on filename as target thus whenever you include a target name inside .PHONY it will regard that thing as such and it will always try to build that target. So its dependent target of that one will also be affected, and thus be built unnecessily.

Symptom

The symptom will show that Makefile will always build a target even without any changes has been made.

Solution

Remove such target from .PHONY.

So in short ...

In short, look at Makefile in this repository, and don't include main.out as part of .PHONY otherwise Makefile will always build main.out (regarded as target) even no changes made.

License

MIT, Wasin Thonkaew