[patch] Fix segfault during inlining of thunk

[Richard Biener]

On Wed, Jan 23, 2019 at 10:48 AM Eric Botcazou <ebotcazou@adacore.com> wrote:
>
> Hi,
>
> this is a regression present in Ada on the mainline since we switched to using
> the internal support for thunks: expand_thunk segfaults during inlining when
> trying to access the DECL_RESULT of the special alias built to make the call
> from the thunk local, if the DECL_RESULT of the thunk is DECL_BY_REFERENCE.
>
> It turns out that neither the C++ nor the Ada front-end builds the DECL_RESULT
> of this special alias (the C++ front-end apparently doesn't even build that of
> the thunk itself so expand_thunk has code to patch this up).  Moreover it's a
> bit strange to first try:
>
>    restmp = gimple_fold_indirect_ref (resdecl);
>
> i.e. build the dereference using the type of resdecl and then use the type of
> the DECL_RESULT of the alias if this failed.  So the attached fix changes this
> to using the type of resdecl in the latter case too.
>
> Bootstrapped/regtested on x86_64-suse-linux, OK for the mainline?

OK.

I guess the original (cut&paste?) error was to look at DECL_RESULT (alias)
instead of DECL_RESULT (thunk_fndecl) which would have made this
consistent as well.

Richard.

>
> 2019-01-22  Eric Botcazou  <ebotcazou@adacore.com>
>
>         * cgraphunit.c (cgraph_node::expand_thunk): When expanding a GIMPLE
>         thunk that returns by reference, use the type of the return object
>         of the thunk instead of that of the alias to build the dereference.
>
>
> 2019-01-23  Eric Botcazou  <ebotcazou@adacore.com>
>
>         * gnat.dg/specs/opt4.ads: New test.
>
> --
> Eric Botcazou