Re: [boost] D-style scope guards?

Subject: Re: [boost] D-style scope guards?
From: Yakov Galka (ybungalobill_at_[hidden])
Date: 2010-09-19 05:37:14

On Sun, Sep 19, 2010 at 08:59, Ulrich Eckhardt <doomster_at_[hidden]> wrote:

> On Friday 17 September 2010 19:56:30 John Bytheway wrote:
> > [...]
> >
> > That won't work in general; std::uncaught_exception might return true
> > because of another pending exception that's going on 'outside' of foo()
> > (e.g. if foo() is called from a destructor).
>

Thank you for the info about std::uncaught_exception. I've never actually
used it.

You could check the function in the constructor of the underlying C++
> object,
> too, in order to detect transitions.
>

Checking in the constructor won't detect transitions. If foo() is called
from a destructor during stack unwinding, then std::uncaught_exception()
will return true twice, even if foo() terminated by yet another exception.
Well, this could work if std::uncaught_exception had returned the number of
pending exceptions. Could be a useful addition to the standard.

On Sun, Sep 19, 2010 at 10:40, Martin Christiansson <
martin.christiansson_at_[hidden]> wrote:

> I've been thinking about a better solution. I need to call a lot of
> C-functions that use return value and errno for error reporting. Writing a
> lot of code around each call is a bit clumsy so I tried to create a guard
> macro instead that puts all relevant data into an exception if the "C
> function" returned an error.
>

If you're to make it a library, it's better to generalize for other APIs.
E.g. use GetLastError() instead of errno for Windows API.

#define RETVALGUARD(COND, FUNC, ...)
>    \
>        conditional_throw_legacy_exception(COND,
>    \
>                                           boost::bind(FUNC, __VA_ARGS__)(),
>    \
>                                           static_cast<const
> char*>(__FILE__),  \
>                                           __LINE__,
>    \
>                                           static_cast<const char*>(# FUNC))
>

Excuse me if I'm wrong again, but why use boost::bind? Why
(FUNC)(__VA_ARGS__) won't work?