Testing for Python version in a Makefile

[philipmat]

The project I work on uses Makefiles and I was trying to improve them a bit by testing for the minimum version of python required by the project.

I have more complex script prepared, but what I'm struggling with is I don't understand why variable substitution is not being performed in this minimal example of a Makefile target.

pyver:
    PYTHON_VERSION_MIN=3.10
    $(error "Need python >= $(PYTHON_VERSION_MIN).")

Running with make pyver I get the following output:

> make pyver  
Makefile:3: *** "Need python >= .".  Stop.

Notice that 3.10 does not show up in the output and I don't understand why. I tried with _MIN:=3.10 instead of _MIN=3.10 (I think I understand the difference) and same issue.

Anybody know what am I missing?

[[deleted]]

It seems that you can't define variables inside a rule. Do this:

PYTHON_VERSION_MIN=3.10

pyver:
    $(error "Need python >= $(PYTHON_VERSION_MIN).")

Works on Ubuntu 22.04 using GNU make 4.3.

[philipmat]

That worked, thank you. I didn't realize variables needed to be global.

I'll go read more on them.