Re: Bug in gcc: assignment to non-lvalue

[Michiel de Bondt <debondt at math dot ru dot nl>]

Using strings to show my point was not a good idea. You can add a field 
"int number" to the struct and perform similar operations (with = 
instead of strcpy).

But even with strings, gcc should give an error like: "strcpy(const 
char*, const char*) does not exists". In case of a "typedef char 
string100[100]", gcc behaves correctly by ringing alarm bells. So it 
seems to be the . operator that behaves incorrectly.

If you replace /*&*/ by & in the SuperArray class, the program becomes 
correct (in my opinion), but also the effect of the program becomes 
different.

Regards, Michiel


Andrew Pinski schreef:
> On 9/20/07, Michiel de Bondt <debondt@math.ru.nl> wrote:
>   
> > struct string100 { char value[100]; };
> >     
>
>   
> >   strcpy (a[0].value, "Non-lvalue assignment."); // illegal
> >     
>
> So you basically have:
> a.operator[](0).value
>
> Where value ia an array, I cannot remember the specific rules here but
> value decays to &value[0] which is considered a rvalue but value[0] is
> a lvalue even if a.operator[](0) is an rvalue.
> So I think GCC is correct in accepting this code.
>
> Thanks,
> Andrew Pinski
>