[compiler-rt] r215247 - [CMake] Determine which compiler-rt librariesare supported on

[Andy Gibbs]

From: Alexey Samsonov 
Sent: Monday, August 18, 2014 9:58 PM
Subject: Re: [compiler-rt] r215247 - [CMake] Determine which compiler-rt librariesare supported on

On Sat, Aug 16, 2014 at 2:33 PM, Andy Gibbs <andyg1001 at hotmail.co.uk> wrote:

  On Saturday, August 09, 2014 12:01 AM, Alexey Samsonov wrote:

    Author: samsonov
    Date: Fri Aug  8 17:01:20 2014
    New Revision: 215247

    URL: http://llvm.org/viewvc/llvm-project?rev=215247&view=rev
    Log:
    [CMake] Determine which compiler-rt libraries are supported on
    a given platform in a top-level CMakeLists.txt to use it both
    in lib/ and in test/ subdirectories. Move architecture/platform
    checks to config-ix.



  Unfortunately your patch breaks builds where special linker flags are used: "try_compile" fails since the user-specified linker flags are overridden.



  Did the build work before the patch? I didn't change the try_compile function, just moved it to separate file. What platform/arch are you building for? Your patch is probably ok, just making sure I understand the cause of the breakage.

Hmm, you're right.  Plus I'd isolated the wrong patch anyway since I'm building from the 3.5 branch and this branched before this patch was committed.  I can't say exactly when the breakage happened, since the previous fully working version I have is the 3.4 release and since then I have only tracked trunk sporadically.  Interestingly, the change to the try_compile function was before the 3.4 branch, so it must be some other change that has highlighted the problem.  In order to get a correct build for llvm, I have to run cmake twice, first with linker flags as part of CMAKE_CXX_FLAGS then separated out into CMAKE_*_LINKER_FLAGS.  The first pass always, and still always, completes successfully.  The second pass now fails with an unable to compile error (missing library).  I imagine somewhere a change has been made to re-evaluate this part of the configuration, causing the failure.  The simple solution, therefore, is simply to pass the linker flags on.

Apologies for the incorrect first assessment.

Cheers
Andy

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