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

[David Froble]

bcjitu at gmail.com wrote:
> 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
> 

But what if the warning is legitimate?  Sounds more like a language 
issue, and it should be fixed, not ignored.