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Re: [PATCH, 4.6 regression]. New error: case label does not reduce

First, if there isn't a bug in Bugzilla for this problem please file one 
so it's properly tracked if it takes a while to work out how to solve it.  
As I understand it from your testcases, it's a matter of certain code that 
is not valid ISO C but you would like to be accepted unless -pedantic, by 
analogy with other such code that is accepted.

On Thu, 16 Feb 2012, Christian Bruel wrote:

> What I'm unsure is why we couldn't have a TREE_NO_WARNING on a
> !CAN_HAVE_LOCATION_P. This seems necessary on some cases without using a

Richard explained this.

What is the code adding TREE_NO_WARNING in the first place (before 
folding) for your testcase?

It may sometimes be safe to copy constants with copy_node to put 
TREE_NO_WARNING on the copies.  But you'd still need to be careful because 
there are some tree-node-equality comparisons for constants, against 
truthvalue_true_node and truthvalue_false_node at least, so those might 
need to be relaxed a bit to allow any non-overflowed integer-type integer 
constant with the right value.

Joseph S. Myers

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