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cmake
mikesol
mikesol

Reputation: 1197

cmake LibFindMacros set library minimum version number

In Cmake, when using LibFindMacros, is there a way to tell cmake that a library needs to have a minimum version number? The information I've found on http://www.cmake.org/Wiki/CMake:How_To_Find_Libraries doesn't say anything about that.

Upvotes: 1

Views: 652

Answers (1)

Alexis Wilke
Alexis Wilke

Reputation: 20741

No... No integrated version support in finding libraries with cmake.

My guess is that in most cases each library has its own way of defining its version and therefore it makes it a daunting task to find out what that version really is. On a Linux system, you could try to query the system with a tool such as dpkg or rpm, but those would only give you the version of the installed library, not the one you're about to compile against.

There is an issue talking about that here:

http://public.kitware.com/Bug/view.php?id=8396

Now, the macros you mentioned have a function to extract a version assuming there is #define <version> <#.#.#> or something of the sort in a header file for that library.

https://github.com/Tronic/cmake-modules/blob/master/LibFindMacros.cmake

# Extracts a version #define from a version.h file, output stored to <PREFIX>_VERSION.
# Usage: libfind_version_header(Foobar foobar/version.h FOOBAR_VERSION_STR)
# Fourth argument "QUIET" may be used for silently testing different define names.
# This function does nothing if the version variable is already defined.
function (libfind_version_header PREFIX VERSION_H DEFINE_NAME)
...

So you use this macro, retrieve a #define from a .h file and then compare that value saved in ${PREFIX}_VERSION in your own way. In my libraries, I often have a set of 3 or 4 #define with the major, minor, and release version numbers. That makes it easy to compare. When you get all those numbers together, such as 3.2.4.1, it makes it harder to compare without specialized code... (again, that makes it really complicated for cmake to support a version comparison scheme.)

Note that the macro expects ${PREFIX}_INCLUDE_DIR to be set. It looks like libfind_pkg_detect() sets that variable so you need to first detect the location of the library (headers) and then you can gather the version in a header.

Update:

Note that there are specialized compare operators you can use to compare two version strings against each other:

if(${PREFIX}_VERSION VERSION_EQUAL 1.2.9)

The only problem is that it's going to be a cmake version comparison algorithm which may not match the corresponding project algorithm. That means it's limited to just numbers separated by periods. I'm not too sure when these operators were added to cmake.

Upvotes: 2

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