Vladimir Prus wrote:
Reece Dunn wrote:
Yes, you're right. However, there's one additional wish -- I'd like an appraoch different macroses for different functions. E.g. for POSIX calls I only encounter -1 returns and NULL returns for error reporting. So I'd like
int tty = check(open(check(ctermid(0)), O_RDRW);
to work. I guess this could be done by providing two overloads for the 'Wrong' function...., but not, the 'Enforcer' template only works for specific type of return value :-(
My errorcheck class (see other posts) has an error policy where you can change the fail test. The default is to test errorcode < 0.
The code you've posted had the check hardcoded, maybe I've missed some other post?
The error_storage::failed() function has the hard-coded check, but the errorcheck class gets the storage (and check) policy as a template, so you can provide your own class to perform a custom check.
A current weakness is that it does not return the value passed to it on assignment, so you cannot use exactly like the above example. I have been updating it to support errno handling, but this (at present) requires something like:
boost::errorcheck< ... > check;
FILE * fp = ::fopen( 0, "r" ); check( fp != 0 ); // assert-like syntax ::fclose( fp );
If you are interested, I'll work on supporting constructs like your example above.
I actually wonder if we need a class. Does it have any advantages over function? E.g:
template<class Checked = default_checker, class T = void> T check(T t) { if (Checker(t)) throw ... return t; }
I suppose it comes down to what you are used to and aesthetics. I have been using MS COM objects heavily that rely on HRESULT error code returns, where the code looks like: HRESULT hr; IHTMLStyle * s = 0; if( FAILED( hr = elem -> get_style( &s ))) goto clean; // use the style object clean: if( elem != 0 ) elem -> Release(); if( s != 0 ) s -> Release(); Which is ugly IMHO, so I use a smart pointer for COM object management and have a com::hresult class for storing the HRESULT, mapping it to a string, etc. The errorcheck class is based on a com::result (throwing version of com::hresult) now defined using errorcheck: typedef boost::errorcheck< hresult > result; I suppose there are applications for both approaches, depending on what style you want, what facilities you want, etc. Regards, Reece _________________________________________________________________ It's fast, it's easy and it's free. Get MSN Messenger today! http://www.msn.co.uk/messenger