[Info-vax] c 7.3 - Why MAYLOSEDATA3 for long pointer math?

[bcjitu at gmail.com]

On Friday, 13 March 2015 13:19:57 UTC+5:30, bcj... at gmail.com  wrote:
> On Monday, 21 July 2014 17:46:39 UTC+5:30, John E. Malmberg  wrote:
> > Hello All,
> > 
> > Can someone explain why the C compiler is generating this warning, and 
> > how to change the code so that the C compiler is happy with out 
> > suppressing the warning message?
> > 
> > All it is doing is subtracting two long pointers and putting the result 
> > in either a unsigned or signed 64 bit value.
> > 
> > LION> cc/point=long/noopt/noobject test64.c
> > 
> >     c = b - a;
> > .......^
> > %CC-W-MAYLOSEDATA3, In this statement, "b-a" has a larger data size than 
> > int.  Assignment can result in data loss.
> > at line number 11 in file VMS_ROOT:[ld_tools]test64.c;10
> > 
> >     d = b - a;
> > .......^
> > %CC-W-MAYLOSEDATA3, In this statement, "b-a" has a larger data size than 
> > int.  Assignment can result in data loss.
> > at line number 12 in file VMS_ROOT:[ld_tools]test64.c;10
> > 
> > 
> > LION> type test64.c
> > #include <types.h>
> > 
> > unsigned __int64 foo(void) {
> > 
> >     char * a = "foo1";
> >     char * b;
> >     unsigned __int64 c;
> >     __int64 d;
> > 
> >     b = &a[2];
> >     c = b - a;
> >     d = b - a;
> > 
> >     return c;
> > }
> > 
> > HP C V7.3-020 on OpenVMS IA64 V8.4
> > HP C V7.3-010 on OpenVMS Alpha V8.4
> > 
> > Regards,
> > -John
> > wb8tyw at qsl.network
> > Personal Opinion Only
> 
> Hi,
> 
> You may disable this warning by adding following line while compiling:
> 
> /WARNINGS = DISABLE = ("MAYLOSEDATA3") NL:
> 
> Regards,
> Jitendra Singh