[cmake-developers] Adding logic to CMake for -fPIE and -fPIC

[Stephen Kelly]

Stephen Kelly wrote:

> Brad King wrote:
> 
>> On 06/05/2012 01:23 PM, Stephen Kelly wrote:
>>> Brad King wrote:
>>>> You can't try_compile inside a platform file.
>>> 
>>> I'm not sure I'm trying to?
>> 
>> I thought you meant you would add the try_compile to the platform file
>> to decide whether to report -fPIE.
>> 
>>> Do you mean in the tests, or do you mean the POSITION_INDEPENDENT_CODE
>>> feature should be disabled for older GCC?
>> 
>> I mean that
>> 
>>   set(CMAKE_${lang}_COMPILE_OPTIONS_PIE "-fPIE")
>> 
>> should not be done if the compiler does not have -fPIE.
>> Therefore Modules/Compiler/GNU.cmake needs to test the
>> compiler version to decide whether -fPIE is available.
> 
> I see. Done for GNU.cmake now at least.
> 

This seems to have caused todays failures:

http://open.cdash.org/buildSummary.php?buildid=2337242

That build has CMAKE_C_COMPILER_VERSION == 4.6.1:

http://open.cdash.org/testDetails.php?test=148901720&build=2337242

but it seems that -fPIE is not added:

http://open.cdash.org/testDetails.php?test=148901721&build=2337242


It doesn't make sense for me to attempt to debug that because I don't have 
access to the box. 

Can someone who has access to one of the boces that is failing like that 
debug it please?

Things to check are:

* Does the test fail when you run it
* Does the test pass when you remove the change to GNU.cmake
* Does the test pass if you replace 

  if(NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 3.4)

with 

  if(NOT CMAKE_${lang}_COMPILER_VERSION VERSION_LESS 3.4)

(I've just patched the code to use that anyway, but please try both to 
confirm if that is the reason for the failure without waiting for tomorrow)

* Does the try_compile source dir correctly contain 

  set(CMAKE_POSITION_INDEPENDENT_CODE ON)

* Does the CMAKE_CXX_COMPILE_OPTIONS_PIE contain "-fPIE" when checked in the 
unit test?

Thanks,

Steve.