[C++ PATCH] Fix GC lambda ICE (PR c++/84455)

[Jason Merrill]

OK.

On Mon, Feb 19, 2018 at 1:56 PM, Jakub Jelinek <jakub@redhat.com> wrote:
> Hi!
>
> While cp_parser_lambda_body which is the other finish_lambda_function
> caller next to tsubst_lambda_expr temporarily increments function_depth
> around that call (if not nested) to avoid GC during expand_or_defer_fn from
> finish_lambda_function, tsubst_lambda_expr doesn't, and on the
> lambda-ice14.C we can see the GC in action in that case.
>
> Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
> trunk?
>
> 2018-02-19  Jakub Jelinek  <jakub@redhat.com>
>
>         PR c++/84455
>         * pt.c (tsubst_lambda_expr): If not nested, increment temporarily
>         function_depth to avoid GC during finish_lambda_function.
>
>         * g++.dg/cpp0x/lambda/lambda-ice26.C: New test.
>
> --- gcc/cp/pt.c.jj      2018-02-16 23:37:29.312364263 +0100
> +++ gcc/cp/pt.c 2018-02-19 10:48:00.328184302 +0100
> @@ -17070,6 +17070,10 @@ tsubst_lambda_expr (tree t, tree args, t
>        bool nested = cfun;
>        if (nested)
>         push_function_context ();
> +      else
> +       /* Still increment function_depth so that we don't GC in the
> +          middle of an expression.  */
> +       ++function_depth;
>
>        local_specialization_stack s (lss_copy);
>
> @@ -17084,6 +17088,8 @@ tsubst_lambda_expr (tree t, tree args, t
>
>        if (nested)
>         pop_function_context ();
> +      else
> +       --function_depth;
>
>        /* The capture list was built up in reverse order; fix that now.  */
>        LAMBDA_EXPR_CAPTURE_LIST (r)
> --- gcc/testsuite/g++.dg/cpp0x/lambda/lambda-ice26.C.jj 2018-02-19 10:51:24.838188732 +0100
> +++ gcc/testsuite/g++.dg/cpp0x/lambda/lambda-ice26.C    2018-02-19 10:51:19.690188624 +0100
> @@ -0,0 +1,5 @@
> +// PR c++/84455
> +// { dg-do compile { target c++11 } }
> +// { dg-options "--param ggc-min-heapsize=0" }
> +
> +#include "lambda-ice14.C"
>
>         Jakub