[CMake] XCode Generation Issue

[Eric Wing]

On 1/20/16, David Morsberger <dave at morsberger.com> wrote:
>
>> On Jan 19, 2016, at 10:11 PM, Eric Wing <ewmailing at gmail.com> wrote:
>>
>> On 1/19/16, David Morsberger <dave at morsberger.com> wrote:
>>> Any help would be appreciated.
>>>
>>> In particular I’d like to know how the default compiler arguments are
>>> set
>>> when ‘cmake -G Xcode’ is executed. The attached file contains the cmake
>>> test
>>> compile extracted and reformatted from CMakeOutput.log that should have
>>> failed. Again, what is setting all the clang compiler options when this
>>> is
>>> executed?
>>>
>>>
>>>
>>> All help is appreciated
>>>
>>>> On Jan 18, 2016, at 2:58 PM, David Morsberger <dave at morsberger.com>
>>>> wrote:
>>>>
>>>> I’m having an issue generating and using a XCode project using cmake
>>>> -G.
>>>>
>>>> cmake —version
>>>>    cmake version 3.4.1
>>>>
>>>> Xcode Version 7.2 (7C68)
>>>>
>>>> Mac OS 10.11.
>>>>
>>>>
>>>> My CMakeLists.txt has a clang option that fails during the -G Xcode
>>>> pass
>>>> but fails when linking within XCode.
>>>>
>>>> The compiler / linker option is ‘-Wl,—as-needed’
>>>>
>>>> The test compile/link step in ‘cmake -G Xcode' creates a long clang
>>>> command with arguments ‘-Wl,—as-needed’ plus ‘—serialize-diagnostics
>>>> <path
>>>> to .dia file>’
>>>>
>>>> The link step within Xcode after the project created has the
>>>> ‘-Wl,—as-needed’ argument and does not have the ‘—serialize-diagnostics
>>>> <path to .dia file>’ argument. The link fails because ‘-Wl,—as-needed’
>>>> isn’t supported.
>>>>
>>>> If copy and execute the long clang command from the ‘cmake -G Xcode’
>>>> command and remove the ‘—serialize-diagnostics <path to .dia file>’
>>>> then
>>>> it successfully fails with ‘-Wl, —as-needed’ isn’t supported.
>>>>
>>>> Finally, when I use cmake to generate unix makefiles it works meaning
>>>> cmake determines ‘-Wl—as-needed’ isn’t supported and doesn’t add it to
>>>> the
>>>> argument list.
>>>>
>>>> Questions:
>>>> - Where is the ‘—serialized-diagnostics’ argument coming from when
>>>> executing ‘cmake -G Xcode’?
>>>>
>>>> - What is a .dia file and how do I read it?
>>>>
>>>> - What’s the preferred / recommended way of detecting the non-supported
>>>> ‘-Wl,—as-needed’ argument during the ‘cmake -G Xcode’ phase? One option
>>>> might to be to remove the ‘—serialize-diagnostics’ argument during the
>>>> generation phase.
>>>>
>>>> I can provide more details on request.
>>>>
>>>> David
>>>>
>>>>
>>>>
>>
>>
>> I just spot checked one of my Xcode compile logs. I see the
>> —serialize-diagnostics flag, but I don't have —as-needed anywhere.
>> Maybe one of your CMake scripts is adding that in, or you have set
>> some kind of environment variable that clang or Xcode is picking up?
>> (This recently happened to me on Linux.)
>
> Ed,
>
> In this case cmake is attempting to determine if ‘—as-needed' is a supported
> option and the build should fail.
>
> I have searched (grep’d) everything I can think of for the string
> ’serialize-diagnostics’ with zero hits.
>
> I can easily add an ‘if( Xcode )’ around the setting in CMakeLists.txt
> however I’m trying to figure out what is exactly going on. The best
> solutions are chosen when you know what is going on under the hood.
>
>
>

I believe the serialize-diagnostics flag is added by Xcode itself. I
see it (along with many other flags) in a native (non-CMake generated)
Xcode project.

-Eric