Re: [C++ PATCH] Avoid -Wreturn-type warnings if a switch has default label, no breaks inside of it, but is followed by a break (PR sanitizer/81275)

[Nathan Sidwell <nathan@acm.org>]

On 11/25/2017 04:01 AM, Jakub Jelinek wrote:

> /* Set if the body of a switch stmt contains a default: case label
>     and does not contain any break; stmts, thus if SWITCH_STMT_BODY
>     is not empty and doesn't fallthru, then the whole switch stmt
>     can't.  */
> #define SWITCH_STMT_CANT_FALLTHRU_P(NODE) \
>    TREE_LANG_FLAG_0 (SWITCH_STMT_CHECK (NODE))
> 
> Seems the C++ FE already has switch_stack, so we could just add there
> a has_default_p, has_break_stmt_p and inside_loop_p flags and both
> inside of templates and outside in finish_case_label, in
> finish_break_stmt if actually adding BREAK_STMT and when entering
> a body of a FOR/DO/WHILE loop tweak those flags.  Seems switch_stack
> is also maintained during pt.c, but we should compute it both during
> parsing and during pt.c (start with the bit clear on a new SWITCH_STMT).
> 
> Thoughts on this?

Sigh, should have read further.  Yes, I'm all for setting such a flag 
during construction.  (I presume doing so is essentially free)

nathan

-- 
Nathan Sidwell