On Fri, 6 Jun 2014, Rich Felker wrote:
> On Fri, May 23, 2014 at 12:26:18PM -0600, Jeff Law wrote: > > On 05/21/14 21:59, Rich Felker wrote: > > >On Wed, May 21, 2014 at 11:17:53AM +0200, Richard Biener wrote: > > >>On Wed, May 21, 2014 at 3:59 AM, Rich Felker <dal...@libc.org> wrote: > > >>>Bug # 61144 is a regression in 4.9.0 that breaks building of musl libc > > >>>due to aggressive and semantically-incorrect constant folding of weak > > >>>aliases. The attached patch seems to fix the issue. A weak alias > > >>>should never be a candidate for constant folding because it may always > > >>>be replaced by a strong definition from another translation unit. > > >>> > > >>>For details see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61144 > > >>> > > >>>I do not have a copyright assignment on file but this patch should be > > >>>sufficiently trivial not to require it. > > >> > > >>Please add a testcase. Also I wonder why it isn't better to generalize > > > > > >How should a testcase be done? On the PR there's a testcase that shows > > >the problem in the generated code, but no automated check for it. > > >Testing this is actually a bit of a pain unless you're allowed to run > > >the generated program. > > You can run the test program. Have it exit (0) on success, abort () > > on failure if at all possible. Then drop the test source file into > > gcc/testsuite/gcc.c-torture/execute/pr61144.c > > The test needs to be two translation units linked together: one with > a weak definition of the object as 0, and the other with a strong > definition. The test should show the weak value being used rather than > the strong one. But I'm not sure how this should be integrated with > the build process. Please have a look at gcc/testsuite/gcc.dg/special/wkali-2{,a,b}.c. This is a three-TU test for weak aliases, so you should be able to very easily adjust it for this bug. Thanks. Alexander
