Re: compile error about destructor

From:
"Ben Voigt [C++ MVP]" <rbv@nospam.nospam>
Newsgroups:
microsoft.public.vc.language
Date:
Wed, 6 Feb 2008 09:48:37 -0600
Message-ID:
<uQSdudNaIHA.5768@TK2MSFTNGP03.phx.gbl>
George wrote:

Thanks Ben,

1.

With /EHa, SEH and C++ exceptions may be mixed, but not in the same


I agree and this is what we proved in his thread before.

2.

function. Separate the __try block body into a separate function.


What do you mean separate the __try block into another function? We


George, why do you always misquote people? I did not say "separate the
__try block into another function", but "Separate the __try block body into
a separate function."

For example, this can't work:

void f(void)
{
    __try {
        this_could_fail();
        auto_ptr<T> temp = new T();
        temp->something_likely_to_fail();
    }
    __finally {
    }
}

The problem is the mixing of C++ destructors with SEH, because both need
unwinding. Whether the destructor for temp should be called depends on
whether the constructor completed. So we make the body of the __try block a
separate function:

void fhelper(void)
{
        this_could_fail();
        auto_ptr<T> temp = new T();
        temp->something_likely_to_fail();
}

void f2(void)
{
    __try {
        fhelper();
    }
    __finally {
    }
}

Now the local inside fhelper can be properly unwound when a structured
exception is thrown, because they exist in a unique stack frame that the
compiler support for SEH knows how to deal with.

always provide try/catch or __try/__except into the same function. I
am confused. Could ytou provide some pseudo code to show your points
please?

regards,
Geprge

"Ben Voigt [C++ MVP]" wrote:

Igor Tandetnik wrote:

"George" <George@discussions.microsoft.com> wrote in message
news:625FF32F-F1B8-4989-B476-8272396CA81A@microsoft.com

I compile with /EHa, and not /EHsc, and this is why I have
confusion there is such error.


Double-check your project settings (perhaps you have a file-level
override). The documentation claims C2712 error should not be
produced under /EHa.


With /EHa, SEH and C++ exceptions may be mixed, but not in the same
function. Separate the __try block body into a separate function.

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