[gambit-list] Re: configure must use -fwrapv as a gcc option for building gambit

feeley at iro.umontreal.ca feeley at iro.umontreal.ca
Fri Jun 3 15:58:29 EDT 2005


Quoting Bradley Lucier <lucier at math.purdue.edu>:

> Here's the documentation for -fwrapv in gcc-4.0 in
> 
> http://gcc.gnu.org/onlinedocs/gcc-4.0.0/gcc/Code-Gen-Options.html#Code- 
> Gen-Options
> 
> -fwrapv
>      This option instructs the compiler to assume that signed arithmetic  
> overflow of addition, subtraction and multiplication wraps around using  
> twos-complement representation. This flag enables some optimizations  
> and disables other. This option is enabled by default for the Java  
> front-end, as required by the Java language specification.
> 
> 
> Since we assume this of all processors, we need to enable this flag.
> 
> Brad
> 

You mean by default gcc will not wrap?  This sounds bogus because it would 
cause major backward compatibility problems.  What happens if you don't 
specify the flag?

Marc




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