[CMake] Checking function or symbol in namespace

[Mateusz Loskot]

Michael Wild wrote:
> On 21. Jan, 2010, at 17:17 , Jed Brown wrote:
> 
>> On Thu, 21 Jan 2010 17:03:27 +0100, Michael Wild 
>> <themiwi at gmail.com> wrote:
>>> But both of them just do a try_compile. I don't see where the 
>>> name-mangling comes in there... If the user wants to check for a 
>>> template, he has to instantiate the template, e.g. 
>>> check_cxx_function_exists("std::copy<std::string::const_iterator,
>>>  std::string::iterator>" "algorithm;string" HAVE_STD_COPY). 
>>> Tedious, but should work. To check for classes, you'd need a 
>>> different macro, however.
>> You're kidding, right?  Have you looked at CheckFunctionExists.c? 
>> It declares the symbol as
>> 
>> char SYMBOL_NAME();
>> 
>> and then tries to link a program that calls this function.  No 
>> headers are included, so there is no way for this symbol to match 
>> the mangled symbol in the library.
>> 
>> Of course, you could write a completely different thing with an 
>> interface more like check_cxx_source_compiles, and call this new 
>> thing check_cxx_function_exists, but that would be terribly 
>> inconsistent so I hope you don't.
>> 
>> Jed
> 
> Ahh, yes. Obviously didn't think it through...

Jed, Michael,

I confess I haven't dug the source of these check macros.

> I have to agree, getting this kind of thing to work with C++ is 
> probably not worth the trouble... Better use a
 > check_cxx_source_compiles in the first place for everything C++.

Yes, though I'd annoyingly keep my side that CXX variants of the macros
would be useful and make C vs C++ separation more clear to user.

Best regards,
-- 
Mateusz Loskot, http://mateusz.loskot.net