Suppressing warning C4290 (when building with MSVC)

[John Emmas <johne53 tiscali co uk>]

Hi guys,

This morning I added these 3 x lines at line 6 of 'glib/glibmm/variant.h' :-

      #ifdef _MSC_VER
      #pragma warning(disable:4290)
      #endif

The added lines suppress hundreds of compiler warnings that I was 
previously getting when trying to build with MSVC.  The warnings all 
took the following form:-

      warning C4290: C++ exception specification ignored except to 
indicate a function is not __declspec(nothrow)

Each warning was generated at a line looking something like this:-

      static V_CastTo cast_dynamic(const VariantBase& v) 
throw(std::bad_cast);

Basically, MSVC (I think) ignores exception specifiers that are too 
specific - e.g. throw(std::bad_cast) - for the reasons stated here:-

http://stackoverflow.com/questions/88573/should-i-use-an-exception-specifier-in-c

Adding the above lines means that I can now build glibmm and giomm 
without seeing any compiler warnings at all which is a big improvement, 
so I thought I might as well flag it up.  There are 5 such exception 
specifiers in variant.h, at lines 408, 436, 680, 866 and 923.  I guess 
different people will have different views so I don't know whether a 
tidier solution would be to remove the offending exception specifiers?  
Or to add the #pragma?  The above article suggests that exception 
specifiers are now deprecated anyway - but OTOH, gcc helpfully generates 
a warning if your code violates the exception specifier(s) so I guess 
that's quite useful.  Regards.

John