On 2015-09-02 17:14:12 -0700, Peter Geoghegan wrote:
> On Wed, Sep 2, 2015 at 12:24 PM, Peter Geoghegan <pg@heroku.com> wrote:
> > On Wed, Sep 2, 2015 at 7:12 AM, Andres Freund <andres@anarazel.de> wrote:
> >> On 2015-07-19 16:34:52 -0700, Peter Geoghegan wrote:
> >> Hm. Is a compiler test actually test anything reliably here? Won't this
> >> just throw a warning during compile time about an unknown function?
> >
> > I'll need to look into that.
>
> My error here was not considering why the existing __builtin_bswap32()
> test worked alright with AC_COMPILE_IFELSE(), while my test needed
> AC_LINK_IFELSE(). I'll be sure to make a point of manually testing
> failure (not just success) when writing compiler tests in the future.
>
> AC_LINK_IFELSE() appears to work fine following a straight
> substitution. When I get around to revising this patch in a while,
> that fix will be included.
Be sure to also test with optimizations enabled - often tests can get
optimized away if you don't force the result to be used (or volatile) :/