Brad King wrote:
> On 05/20/2013 09:42 AM, Stephen Kelly wrote:
>> set(CMAKE_DEFAULT_VISIBILITY hidden)
>>
>> add_library(foo ...)
>> add_library(bar ...)
>> add_library(bat ...)
>> set_property(TARGET bat PROPERTY DEFAULT_VISIBILITY default)
>>
>> I know this is only a bit nicer. It's an idea worth raising though if we
>> want to move away from strings for compile flags to lists of compile
>> options.
>
> Thanks for the explanation. (I assume you meant
> s/DEFAULT_VISIBILITY/VISIBILITY_DEFAULT/ in your example.)
Yes. I've been backward and forward over what to call that property while
implementing it.
>>> Unlike PIC, visibility is not a usage requirement, is it?
>>
>> I'm not sure either. My vague understanding is that it might be needed
>> for plugins. That seems to be true for Windows, but I haven't checked on
>> linux yet. According to a comment in a KDE cmake file, it is apparently.
>> kdelibs fails at cmake time if Qt is not built with hidden visibility.
>
> That sounds like the other way around. Qt is a dependency of kdelibs.
> If Qt wasn't built with hidden visiblity then kdelibs cannot change its
> build to make things work. It is more of a usage check/error.
True. I guess making this a usage requirement doesn't make sense.
>>>> How should visibility-inlines-hidden be handled? Introduce
>>>> CMAKE_${lang}_COMPILE_OPTIONS_VISIBILITY_INLINES_HIDDEN and use it if
>>>> VISIBILITY_DEFAULT == "hidden"?
>>
>> There is also an option for use with MinGW on Windows, which seems
>> roughly equivalent: -fno-keep-inline-dllexport.
>>
>> Could I make CMAKE_${lang}_COMPILE_OPTIONS_VISIBILITY_INLINES_HIDDEN
>> apply that too?
>
> They do look quite similar. Might there ever be a reason one would
> want -fvisibility-inlines-hidden but not -fno-keep-inline-dllexport
> on the respective platforms?
The -fno-keep-inline-dllexport option has no effect on non MinGW:
stephen@hal:~/cpp$ g++ -fno-keep-inline-dllexport
g++: error: command line option ‘-fno-keep-inline-dllexport’ is not
supported by this configuration
g++: fatal error: no input files
compilation terminated.
I don't know if MinGW ignores the visibility entirely (and relies only on
the dllimport/dllexport setting). At least the compiler accepts the argument
and the dirver passes it on to cc1plus.
>
> In my understanding of your proposal, VISIBILITY_DEFAULT == "hidden"
> will add -fvisibility=hidden *and* -fvisibility-inlines-hidden.
> Should we have a way to skip the latter e.g. "hidden-no-inlines"?
Perhaps. If we can figure out how to name everything.
Thanks,
Steve.
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