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Re: [RFC PATCH 0/1] Implement CMake build

From
JHJeff Hostetler <git@jeffhostetler.com>
Date
Jan 26, 2018, 17:34 UTC
Message-ID
<c134350c-5f73-9194-9815-a7f61ed30d03@jeffhostetler.com>
In-Reply-To
<CAG6xkCa_nKtzhJJq=v7gazWe+8FnN3mz1vDftzZw2WUFqJ1bzw@mail.gmail.com>
On 1/25/2018 7:21 PM, Isaac Hier wrote:
Show 28 quoted lines
> Hi Jeff,
> 
> I have been looking at the build generator, which looks promising, but
> I have one concern. Assuming I can generate a CMakeLists.txt that
> appropriately updates the library sources, etc. how do you suggest I
> handle new portability macros? For example, assume someone adds a
> macro HAVE_X to indicate the availability of some platform-specific
> function x. In the current Makefile, a comment would be added to the
> top indicating when HAVE_X or NO_X should be set, and that option
> would toggle the HAVE_X C macro. But CMake can test for the
> availability of x, which is one of the main motives for adding a CMake
> build. The current build generator uses the output of make, so all it
> would know is whether or not HAVE_X is defined on the platform that
> ran the Makefile, but not the entire list of platform that git
> supports.
> 
> Bottom line: should I add the portability tests as they are now,
> without accounting for future portability macros? One good alternative
> might be to suggest the authors of new portability macros include a
> small sample C program to test it. That would allow me to easily patch
> the CMake tests whenever that came up. In a best case scenario, a
> practice could be established to write the test in a specific
> directory with a certain name so that I could automatically update the
> CMake tests from the build generator.
> 
> Thanks for the help,
> 
> Isaac

It's been years since I've used cmake as anything other than a casual (downstream) consumer, so I'm not sure I can answer your questions.

The vcxproj target we have is a bit of a hack to automatically capture the set of source files and target libraries and executables. We don't try to capture the spirit of all of the HAVE_ and NO_ flags when we build the *.vcxproj files. And we make some assumptions in the generation template for the usual VC/VS settings. But then Windows is a single target and we don't have to worry about some things (like whether or not qsort is present).

I don't want to discourage you from attempting this. (And I realize that my initial response might have given that impression -- I mainly wanted to say that we don't currently have a problem on Windows with the current Makefile situation.)

A full cmake system would let us simplify some things, but it also complicates some things. So we might be trading one set of problems for another. For example, the libgit2 project uses cmake. Not to pick on them, but when I look at it, I see a lot of the same issues (but perhaps with better syntax than the makefile).

     https://github.com/libgit2/libgit2/blob/master/CMakeLists.txt

As to your portability test questions, I'm afraid I don't know. Sorry, Jeff

Previous: Isaac HierNext: Robert Dailey
Message 16 of 18 in “Implement CMake build”
  1. 0/1 Implement CMake buildIsaac Hier, Jan 23, 2018
  2. 1/1 Implement CMake buildIsaac Hier, Jan 23, 2018
  3. Isaac HierJan 24, 2018
  4. Jacob KellerJan 24, 2018
  5. Junio C HamanoJan 24, 2018
  6. Ævar Arnfjörð BjarmasonJan 24, 2018
  7. Stephan BeyerJan 24, 2018
  8. Isaac HierJan 24, 2018
  9. Stephan BeyerJan 24, 2018
  10. Isaac HierJan 25, 2018
  11. Jeff HostetlerJan 24, 2018
  12. Isaac HierJan 24, 2018
  13. Jeff HostetlerJan 24, 2018
  14. Isaac HierJan 24, 2018
  15. Isaac HierJan 26, 2018
  16. Jeff HostetlerJan 26, 2018
  17. Robert DaileyFeb 20, 2018
  18. Isaac HierFeb 23, 2018

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