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 11/24/2017 04:59 PM, Jakub Jelinek wrote:
> Hi!
> 
> The testcase below has a useless break; that causes a bogus -Wreturn-type
> warning.  The C++ FE already has code to avoid adding a BREAK_STMT
> after a return or similar sequence that is known not to return.
> The following patch extends block_may_fallthrough to also return false
> for SWITCH_STMTs that can't fall through.
> 
> Those are ones with non-empty body where the whole body can't fallthrough,
> additionally they need to have a default: case label (or cover the whole
> range of values, but that is not what this patch can compute, that would
> be too big duplication of the gimplification processing) and no BREAK_STMT.
> 
> For the default: case label we need to look in all SWITCH_BODY children
> except for nested SWITCH_STMTs, for BREAK_STMTs also not in
> {FOR,DO,WHILE}_BODY.
> 
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
> 
> 2017-11-24  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR sanitizer/81275
> 	* cp-objcp-common.c (struct find_default_and_break_s): New type.
> 	(find_default_and_break): New function.
> 	(cxx_block_may_fallthru): Return false for SWITCH_STMT which
> 	contains no BREAK_STMTs and contains a default: CASE_LABEL_EXPR.
> 
> 	* g++.dg/warn/pr81275.C: New test.

ok


-- 
Nathan Sidwell