Re: [xml] An xmlXPathTypeVal is never equal to XML_NAMESPACE_DECL

On Wed, Sep 26, 2012 at 3:21 AM, Daniel Veillard <veillard redhat com> wrote:
On Tue, Sep 25, 2012 at 04:21:34PM +0100, Hans Wennborg wrote:

We're using libxml2 in Chromium, and I just noticed that recent
versions of Clang have started warning about the following code:

warning: comparison of constant 18 with expression of type
'xmlXPathTypeVal' is always false
                        if (type == XML_NAMESPACE_DECL)
                            ~~~~ ^  ~~~~~~~~~~~~~~~~~~

In the latest version of xpath.c, the code is still there, but on line 12402.

Looking at the code, 'type' is a variable of type 'xmlXPathTypeVal',
whereas XML_NAMESPACE_DECL is an enumerator in 'xmlElementType'.

Clang warns because the 'xmlXPathTypeVal' type is not wide enough to
hold the value of XML_NAMESPACE_DECL, and therefore the comparison
will never be true.

I've tried to figure out what a good fix would be here, but I don't
know the code well enough. It would be great if someone could advice
on the best way to fix this.

  You need a bit more context, the code fragment is:

                    } else if (cur->type == type) {
                        if (type == XML_NAMESPACE_DECL)
                    } else if

 So yes the comparison is done to the wrong type ... but the line
before we checked that type and cur->type have the same value !

We can change the test to:

                        if (cur->type == XML_NAMESPACE_DECL)

this will silent Clang, but the semantic should be exactly the same
(as far as I know equality is transitive even in C :-)
I'm  pushing the change,

Yup, that should fix it! Thanks very much.

 - Hans

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