[SOLVED] Use value from C/C++ macro in CMake

Issue

What is the easiest way to get the value of a C/C++ macro into a CMake variable?

Given I check for a library libfoo with the header foo.h. I know foo.h contains the macro #define FOO_VERSION_MAJOR <version> where version is an integer or string value. To extract the major version of the found library, I want to use the value from this macro.

As a bonus, if the macro is not found, this could indicate a version older then a specific version introducing the version macro.

Solution

I'd go with file(READ ...) to read the header followed by string(REGEX ...) to extract desired define.

Example code:

file(READ "foo.h" header)
string(REGEX MATCH "#define FOO_MAJOR_VERSION [0-9]+" macrodef "${header}")
string(REGEX MATCH "[0-9]+" FooMajorVersion "${macrodef}")

Answered By - arrowd

Answer Checked By - Robin (WPSolving Admin)