On Thu, Jun 27, 2019 at 10:18 AM Alexandre Oliva <[email protected]> wrote:
>
> The only preexisting use of GIMPLE_EH_ELSE, for transactional memory
> commits, did not allow exceptions to escape from the ELSE path. The
> trick it uses to allow the ELSE path to see the propagating exception
> does not work very well if the exception cleanup raises further
> exceptions: the ELSE block is configured to handle exceptions in
> itself. This confuses the heck out of CFG and EH cleanups.
>
> Basing the lowering context for the ELSE block on outer_state, rather
> than this_state, gets us the expected enclosing handler.
>
> Regstrapped on x86_64-linux-gnu. Ok to install?
Testcase?
>
> for gcc/ChangeLog
>
> * tree-eh.c (honor_protect_cleanup_actions): Use outer_
> rather than this_state as the lowering context for the ELSE
> seq in a GIMPLE_EH_ELSE.
> ---
> gcc/tree-eh.c | 13 ++++++++-----
> 1 file changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/gcc/tree-eh.c b/gcc/tree-eh.c
> index 23c56b5661a1..4de09d1bf7b5 100644
> --- a/gcc/tree-eh.c
> +++ b/gcc/tree-eh.c
> @@ -1001,11 +1001,14 @@ honor_protect_cleanup_actions (struct leh_state
> *outer_state,
> gimple_try_set_cleanup (tf->top_p, gimple_eh_else_n_body (eh_else));
> finally = gimple_eh_else_e_body (eh_else);
>
> - /* Let the ELSE see the exception that's being processed. */
> - eh_region save_ehp = this_state->ehp_region;
> - this_state->ehp_region = this_state->cur_region;
> - lower_eh_constructs_1 (this_state, &finally);
> - this_state->ehp_region = save_ehp;
> + /* Let the ELSE see the exception that's being processed, but
> + since the cleanup is outside the try block, process it with
> + outer_state, otherwise it may be used as a cleanup for
> + itself, and Bad Things (TM) ensue. */
> + eh_region save_ehp = outer_state->ehp_region;
> + outer_state->ehp_region = this_state->cur_region;
> + lower_eh_constructs_1 (outer_state, &finally);
> + outer_state->ehp_region = save_ehp;
> }
> else
> {
>
> --
> Alexandre Oliva, freedom fighter he/him https://FSFLA.org/blogs/lxo
> Be the change, be Free! FSF Latin America board member
> GNU Toolchain Engineer Free Software Evangelist
> Hay que enGNUrecerse, pero sin perder la terGNUra jamás - Che GNUevara
