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Re: [RFC PATCH] -Wmemset-transposed-args (PR middle-end/61294)

On 07/08/2014 12:38 PM, Carlos O'Donell wrote:
What rationale would you give for not warning on 1-1?

Because it's not likely to be a case of argument transposition; it's more likely to be an expression that just happens to evaluate to 0, which is fine as a length argument to memset.

On 07/08/2014 01:31 PM, Jakub Jelinek wrote:
On Tue, Jul 08, 2014 at 03:24:52PM -0400, Jason Merrill wrote:
I don't think we want to warn about e.g. 1-1, only about literal 0.

Well, at least literal 0 and '\0'.

Right, I consider '\0' to be a literal 0.

But in the C++ FE there isn't something like that.  Do you think we
shouldn't warn even if e.g. the last argument is a template parameter
that turns out to be 0, so warn only during parsing and check for literal
0 and not warn again during instantiation?

Yes, that's what I think.

Any suggestions how to find out
if it was literal 0 or something that folded to 0 in the C++ FE?

I suppose we could use an INTEGER_CST distinct from the one in TYPE_CACHED_VALUES for raw 0, with a TREE_LANG_FLAG set.


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