confusion about string.erase( --string.end() )

Ian Lance Taylor iant@google.com
Tue Nov 22 18:18:00 GMT 2011


Pawel Sikora <pluto@agmk.net> writes:

> afaics the gcc-4.6 accepts following code:
>
> #include <string>
> int main()
> {
>         std::string line( "blabla" );
>         line.erase( --line.end() );
> }
>
> but other compilers reject such code:
>
> msvc8  : error C2105: '--' needs l-value
> comeau : error: expression must be a modifiable lvalue
>
> is it a bug in g++?

I don't think this is a bug.  std::string::end is required to return a
std::string::iterator.  The type of std::string::iterator is
implementation defined.  It so happens that the g++ implementation of
std::string::iterator has an operator-- method.  Apparently this is not
true of the implementations used by MSVC or Comeau.  So it's not a bug,
it's just an implementation difference permitted by the standard.

Ian



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