Why do I get this error?

[Luis Pedro Coelho]

Em Domingo, 10 de Novembro de 2002 17:12, Ian Reinhart Geiser escreveu:
> > > /usr/local/src/kdelibs/kabc/plugins/ldap/resourceldap.cpp:98: cannot
> > > convert `QCString()' from type `QCString' to type `char *'
> >
> > Does an explicit cast like
> >   (char*)mHost.local8Bit()
> > or
> >   (const char*)mHost.local8Bit()
> > help?
>
> This must be a gccism... the (char *) fails with the same error, but the
> (const char *) only gives a warning of discarded qualifiers...
>
> What is the lesser of evils?

gcc is right, though. There is only an QCString::operator const char*() const. 
No direct conversion to char*. 

The (const char*) cast helps the compiler find it and call it, but then you 
try to use it as a char* and it warns you that you are discarding const (if 
am looking at the right thing, you are calling ldap_init which takes a char*, 
no const qualifier). This is, in fact, illegal c++ and therefore the warning. 

You can either leave the warning, though it might cause graver problems in 
other gcc versions / other compilers or go the long way around to do it 
correctly:

const_cast<char*>(static_cast<const char*>(mHost.local8Bit())).

Cast to const char* using the user-defined operator and cast away the 
const-ness.

HTH,
-- 
Luis Pedro Coelho

"Technology does not always equal progress."
Douglas Coupland