#ifdef _JBLEN not portable

[Kaveh R. Ghazi]

 > From: grahams@rcp.co.uk
 > 
 > Hi
 > 
 > The use of "#ifdef _JBLEN" in toplev.h to determine if jmp_buf is
 > defined is not portable. On my x86-linux + glibc-2.0.6 system setjmp.h
 > is included before toplev.h and yet the prototype for
 > set_float_handler() is excluded because _JBLEN is not defined.
 > 
 > This means that files which use set_float_handler() and include both
 > setjmp.h and toplev.h do not always see a prototype for
 > set_float_handler depening on whether setjmp.h defines _JBLEN
 > 
 > This problem occurs anytime a system dependent define (here I am
 > refering to the name and not what its defined as) to conditionalise
 > the inclusion of a prototype.all define is used
 > 
 > Any suggestion onto how to elimate this system dependency. Here are
 > some to start with
 > 
 > 1. include <setjmp.h> in toplev.h so jmpbuf is always defined.
 > 
 >   This probably goes against egcs coding standards
 > 
 > 2. move setjmp stuff to system.h


	Since both toplev.h and system.h are included in almost every
file, choices 1&2 would both end up doing the same thing.  That is,
every C file would get setjmp.h.  Some egcs developers don't like it
when a header only needed in a couple of files gets included
everywhere, so I'd like to shy away from these solutions.




 > 3. include <setjmp.h> indirectly via a egcs specific include files
 >     which also egcs specific define "HAS_SETJMPBUF" or
 >     whatever.
 > 
 > Graham  


	Choice #3 would work, but IMHO its kind of overkill for this
problem and introduces extra of hair. :-)


A lower impact alternative would be to find a macro defined in glibc's
setjmp.h and change the test in toplev.h to check _JBLEN as well as
this new one which you could choose for us.  Eg: 

 > #if defined(_JBLEN) || defined(<SOMETHING_DEFINED_IN_GLIBC_SETJMP_H>)
 > extern void set_float_handler PROTO((jmp_buf));
 > #endif

	Another alternative would be to forgo the prototype argument when
setjmp.h doesn't define _JBLEN.  Eg:

 > #ifdef _JBLEN
 > extern void set_float_handler PROTO((jmp_buf));
 > #else
 > extern void set_float_handler ();
 > #endif

	I much prefer the first solution since it gets us the proto
argument.  The second one just papers over it.

		--Kaveh
--
Kaveh R. Ghazi			Project Manager / Custom Development
ghazi@caip.rutgers.edu		Icon CMT Corp.