[boost] feed_args.hpp bug (and patch)

From: Paul Hamilton (paul_at_[hidden])
Date: 2003-08-20 22:21:37

I have found a bug in boost/format/feed_args.hpp.

The simple declaration of a static variable in a header like this:

static int x;

Is "allowed" in GCC, but in darwin, when you try to compile this code 
into a "dll" (dynamic-linking), then link using ld, ld will complain 
about "common symbols not allowed with MH_DYLIB output format". This 
may also be the general case with all platforms, but I haven't been 
able to test this.

The correct solution for the above case is, in all headers use:

extern int x;

And in a single place in the implementation:

int x = 0;

Of course the code in feed_args.hpp doesn't even really NEED a global 
variable, so as a solution (rather than try to introduce the above 
complicated change just for one platform), I propose that we change the 
code:

        static const std::basic_string<Ch, Tr> emptyStr;

To:

        const std::basic_string<Ch, Tr> emptyStr = "";

Which basically does exactly the same thing.

Here is my patch to feed_args.hpp:

------------------------  feed_args.hpp.patch ------------------------
*** feed_args.hpp	Wed Aug 20 18:50:10 2003
--- feed_args.hpp.org	Wed Aug 20 18:50:12 2003
***************
*** 34,42 ****

     template<class Tr, class Ch> inline
     void empty_buf(BOOST_IO_STD basic_ostringstream<Ch,Tr> & os) {
!   	// PTH 20/8/2003 - need this to NOT be a static for certain 
compilers.
!   	// we also don't really need this to be a global variable.
! 	const std::basic_string<Ch, Tr> emptyStr = "";
       os.str(emptyStr);
     }

--- 34,40 ----

     template<class Tr, class Ch> inline
     void empty_buf(BOOST_IO_STD basic_ostringstream<Ch,Tr> & os) {
! 	static const std::basic_string<Ch, Tr> emptyStr;
       os.str(emptyStr);
     }
------------------------  feed_args.hpp.patch ------------------------

---------------------
Paul Hamilton
pHamtec P/L - Software Makers
http://www.phamtec.com/
mailto:paul_at_[hidden]

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