Re: BZSUPPORT: Linking problems with egcs-2.91.66 (egcs-1.1.2 release)

[Todd V. <tve...@ex...>]

Hi Volker,

Volker Dobler P945 <vol...@un...> wrote:
> I am using blitz heavily in a larger project wich is
> split into several source files.  I have a main source file
> where several global arrays are defined like
> 
> Array<double,1>  T(initial_Array_size);
> 
> In the other source files these are declared like
> 
> extern Array<double,1>  T;
> 
> Everything worked fine until we installed a new version
> of egcs:  gcc version egcs-2.91.66 19990314/Linux (egcs-1.1.2 release)
> Every source file still compiles fine, but during linking I get
> several of the following error messages:
> 
> io.o: warning: multiple common of `blitz::MemoryBlockReference<double>::nullBlock_'
> annealing.o: warning: previous common is here
> io.o: warning: multiple common of `__sn_Q25blitzt20MemoryBlockReference1Zd.nullBlock_'
> annealing.o: warning: previous common is here
> init.o: warning: multiple common of `blitz::MemoryBlock<double> type_info node'
> annealing.o: warning: previous common is here
> 
> What's going wrong?
> Am I making a stupid C++ error so that the templates get instantiated
> multiple times, or is this a known problem with this version of egcs?

Here's the situation: blitz::Array inherits from a class
blitz::memoryBlockReference<T>.  That class requires that
a global static object 
   blitz::MemoryBlock<T> MemoryBlockReference<T>::nullBlock_;
be instantiated.
It looks like gcc is instantiating this object multiple times, then
the linker is warning you about these duplicate instances.

I don't think these warnings are anything to worry about.
You might check if there is a flag to suppress them.

Also, if anyone has suggestions for dealing with static global template
instances, please let me know.

Cheers,
Todd
-- 
Todd Veldhuizen               tve...@ac...
Indiana Univ. Comp. Sci.      http://extreme.indiana.edu/~tveldhui/

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