Multiplication bug on EDE Crossview for M16C?

Hi to all
recently i noticed a strange behavior debugging a a simple code that i wrote
in C for the Mitsubishi-Renesas microcontroller M16C:

void Function_multiply(void)
{
    unsigned char term1,term2,result;
    term1=6;
    term2=8;

    result= term1 * term2;
}
I expect that result=48 ,with no loss of data,being the 2 terms small
numbers

instead i have result=6 ,same with other small numers

To have result=48 i need to declare the local variable as unsigned int.

I dont think that i s a real bug,but i find strange that some option in the
compiler could generate this unexpecyed situation

Thanks you for your attention
Have a nice weekend

Diego,Milan
Italy

blisca wrote:

> recently i noticed a strange behavior debugging a a simple code that i wrote
> in C for the Mitsubishi-Renesas microcontroller M16C:
> 
> void Function_multiply(void)
> {
>     unsigned char term1,term2,result;
>     term1=6;
>     term2=8;
> 
>     result= term1 * term2;
> }
> I expect that result=48 ,with no loss of data,being the 2 terms small
> numbers
> 
> instead i have result=6 ,same with other small numers
> 
> To have result=48 i need to declare the local variable as unsigned int.
> 
> I dont think that i s a real bug,but i find strange that some option in the
> compiler could generate this unexpecyed situation

If this is the exact code that you were using, how did you verify the 
result ?

As stated, the function has no side effects, and the result value is 
ignored, so the compiler is free to optimize (part of) the function body 
away. If you use a debugger to look at the result, your results may not 
be reliable.

On Sat, 09 Feb 2008 08:44:33 -0000, Arlet Ottens <usenet+5@c-scape.nl>  =

wrote:

> blisca wrote:
>
>> recently i noticed a strange behavior debugging a a simple code that =
i  =

>> wrote
>> in C for the Mitsubishi-Renesas microcontroller M16C:
>>  void Function_multiply(void)
>> {
>>     unsigned char term1,term2,result;
>>     term1=3D6;
>>     term2=3D8;
>>      result=3D term1 * term2;
>> }
>> I expect that result=3D48 ,with no loss of data,being the 2 terms sma=
ll
>> numbers
>>  instead i have result=3D6 ,same with other small numers
>>  To have result=3D48 i need to declare the local variable as unsigned=
 int.
>>  I dont think that i s a real bug,but i find strange that some option=
  =

>> in the
>> compiler could generate this unexpecyed situation
>
> If this is the exact code that you were using, how did you verify the =
 =

> result ?
> As stated, the function has no side effects, and the result value is  =

> ignored, so the compiler is free to optimize (part of) the function bo=
dy  =

> away. If you use a debugger to look at the result, your results may no=
t  =

> be reliable.
>

It would be very helpful to see what assembly is produced, if the assemb=
ly
is correct then the compiler is fine and its probably a debugger fault. =
  =

Interesting
tho.

"Arlet Ottens" <usenet+5@c-scape.nl> ha scritto nel messaggio
news:47ad67f2$0$85785$e4fe514c@news.xs4all.nl...
> blisca wrote:
>
> > recently i noticed a strange behavior debugging a a simple code that i
wrote
> > in C for the Mitsubishi-Renesas microcontroller M16C:
> >
> > void Function_multiply(void)
> > {
> >     unsigned char term1,term2,result;
> >     term1=6;
> >     term2=8;
> >
> >     result= term1 * term2;
> > }
> > I expect that result=48 ,with no loss of data,being the 2 terms small
> > numbers
> >
> > instead i have result=6 ,same with other small numers
> >
> > To have result=48 i need to declare the local variable as unsigned int.
> >
> > I dont think that i s a real bug,but i find strange that some option in
the
> > compiler could generate this unexpecyed situation
>
> If this is the exact code that you were using, how did you verify the
> result ?
>
> As stated, the function has no side effects, and the result value is
> ignored, so the compiler is free to optimize (part of) the function body
> away. If you use a debugger to look at the result, your results may not
> be reliable.
>
thanks for helping me
No,this is not the exact code,in fact i use the result and it leads me to a
bigger error
let me know your hints

Diego

"Dave" <dave@dave.com> ha scritto nel messaggio
news:op.t585lgzy22usyq@edl_laptop1.belkin...
On Sat, 09 Feb 2008 08:44:33 -0000, Arlet Ottens <usenet+5@c-scape.nl>
wrote:

> blisca wrote:
>
>> recently i noticed a strange behavior debugging a a simple code that i
>> wrote
>> in C for the Mitsubishi-Renesas microcontroller M16C:
>>  void Function_multiply(void)
>> {
>>     unsigned char term1,term2,result;
>>     term1=6;
>>     term2=8;
>>      result= term1 * term2;
>> }
>> I expect that result=48 ,with no loss of data,being the 2 terms small
>> numbers
>>  instead i have result=6 ,same with other small numers
>>  To have result=48 i need to declare the local variable as unsigned int.
>>  I dont think that i s a real bug,but i find strange that some option
>> in the
>> compiler could generate this unexpecyed situation
>
> If this is the exact code that you were using, how did you verify the
> result ?
> As stated, the function has no side effects, and the result value is
> ignored, so the compiler is free to optimize (part of) the function body
> away. If you use a debugger to look at the result, your results may not
> be reliable.
>

It would be very helpful to see what assembly is produced, if the assembly
is correct then the compiler is fine and its probably a debugger fault.
Interesting
tho.

ok,but i have it at work so i have to wait til next week to copy the section
relative to the problem
many thanks to you

have you all a nice weekend