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Re: breakpoints in constructors

On Thu, Apr 24, 2003 at 06:02:24PM -0400, Paul Koning wrote:
> >>>>> "Daniel" == Daniel Jacobowitz <drow at mvista dot com> writes:
>  Daniel> On Fri, Apr 18, 2003 at 01:04:46PM -0700, David Carlton
>  Daniel> wrote:
>  >> I might have some time over the next few weeks (/months) to work
>  >> on the "breakpoints in constructors" issue.  Daniel: clearly
>  >> you've thought about this already, so if you happen to have time
>  >> to do a bit of a brain dump on the issue at some point, I'd
>  >> appreciate it.
>  Daniel> Sure.  First of all, a rough overview of the problem; might
>  Daniel> as well keep everything in one place.
>  Daniel> With the new GCC 3.x multi-vendor C++ ABI, constructors are
>  Daniel> implemented as multiple functions: C1, the complete object
>  Daniel> constructor [in-charge] C2, the base object constructor
>  Daniel> [not-in-charge] C3, the allocating constructor [not currently
>  Daniel> used]
>  Daniel> Similarly for destructors - most of the rest of this message
>  Daniel> applies to destructors too.  The base constructor is
>  Daniel> generally called for the base objects of a derived class,
>  Daniel> esp. with virtual inheritance; it's been a while since I
>  Daniel> looked at exactly when.
>  Daniel> GCC has chosen to implement this by duplicating the function,
>  Daniel> including any user-provided code and any compiler-added code.
>  Daniel> A better implementation would have one copy and labels for
>  Daniel> multiple entry points, on systems where that is supported;
>  Daniel> that's temporarily tabled pending a better description of the
>  Daniel> GCC tree structure to describe multiple entry points.
> Maybe this is off base, but Fortran has always had multiple entry
> points, and GCC supports Fortran (g77), so presumably there is a way
> to represent this in the tree structure already.

I believe that by the time Fortran hands off, we're not in trees any
more - that's been a longstanding complaint about g77, it RTLs too
easy.  But I might be mistaken about that.

Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer

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