Remove old CMake code about gcc version check for -frounding-math

[mglisse]

cgal/Installation/CMakeLists.txt

Lines 463 to 466 in b8e342d

	if("${GCC_VERSION}" MATCHES "^[4-9].")
	message(STATUS "Using gcc version 4 or later. Adding -frounding-math")
	uniquely_add_flags(CGAL_CXX_FLAGS "-frounding-math")
	endif()

Does gcc version 10 match this condition?

[lrineau]

That is an old code, that should be removed, because it is useless. The actual way -frounding-math is added is:

cgal/Installation/cmake/modules/CGAL_SetupCGALDependencies.cmake

Lines 158 to 161 in 0bd75b7

	if(CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 3)
	message( STATUS "Using gcc version 4 or later. Adding -frounding-math" )
	target_compile_options(${target} INTERFACE "$<$<COMPILE_LANGUAGE:CXX>:-frounding-math>")
	endif()

[afabri]

If it is an old code that should be removed why don't you remove it instead of closing the issue? It sounds trivial, but I certainly miss something here.

[lrineau]

The issue is about Marc worrying that -frounding-math would not be correctly added with gcc version 10 or later. And it is not.

There are a lot of unused parts of CMake files that could be removed, but that would require several days of work, and that would be only a cosmetic refactoring, without any change of behavior. That is not my priority for the moment. If anybody is willing to submit a pull-request, I will review it.

[albert-github]

I agree with @afabri especially as this is now known so not that difficult to create a pull request.

There are a lot of unused parts of CMake files that could be removed, but that would require several days of work, and that would be only a cosmetic refactoring, without any change of behavior. That is not my priority for the moment. If anybody is willing to submit a pull-request, I will review it.

This is true but it is also error prone as when the CMake files are changed the engineer will think "what is going on here".

As part of the statement in the quote is:

... There are a lot of unused parts of CMake files that could be removed ...

• Is there a list of these know unused parts?
• Is there already an issue to tackle this problem?

Unfortunately (?) I'm lacking the knowledge about the valid versions of the different parts CGAL otherwise I might have had a go at it.

Regarding this specific problem we see that for testing the GCC compiler version there are different type of tests some based on GCC_VERSION other on the more general CMAKE_CXX_COMPILER_VERSION (sometimes even in the same file e.g. Installation/cmake/modules/CGAL_SetupCGALDependencies.cmake).
Also the test on using the GCC compilers is done in different ways sometimes by CMAKE_COMPILER_IS_GNUCCX and on other places by CMAKE_CXX_COMPILER_ID MATCHES "GNU".
So this could be a bit more consistent as well...

[lrineau]

I reopen this issue until somebody is willing to create a pull-request to "solve" it.

[afabri]

I raised the question, as it sounded as removing a couple of lines. If it is more complex I agree with Laurent that we have to set priorities. But keeping the issue open and put it in a task list is certainly a better idea than just closing it.