Re: Parameter Modes, In In Out and Out

[Laurent Guerby <guerby@acm.org>]

Robert Dewar <robert_dewar@my-deja.com> writes:
> Laurent Guerby <guerby@acm.org> wrote:
> > if your compiler uses by copy passing
> > for integer, you'll probably get a program_error, because the
> > generated code for exiting P will set X with an unitialized
> > stack value (the place reserved for the Y value).
> 
> All compilers MUST pass integers by copy, there is no choice.

Yes (unless an appropriate pragma is used to overide the mandated Ada
passing convention). My wording was sloppy, I meant to talk at the
generated code level, not at the Ada copy out semantic here.

The idea is that for my example code, the compiler could have done
many things, and you'll get the user program_error if and only if the
compiler did copy out the parameter at the code level. Other valid
behaviours are (I believe) to remove the call, not to copy out,
friendly raise some exception at procedure exit, etc... (hence the
"probably").

-- 
Laurent Guerby <guerby@acm.org>