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From: "glisse at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/58950] New: [4.9 Regression] Missing "statement has no effect"
Date: Thu, 31 Oct 2013 23:11:00 -0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: c++
X-Bugzilla-Version: 4.9.0
X-Bugzilla-Keywords: diagnostic
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58950

            Bug ID: 58950
           Summary: [4.9 Regression] Missing "statement has no effect"
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Keywords: diagnostic
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: glisse at gcc dot gnu.org

void f(){
  int i __attribute__((vector_size(2*sizeof(int)))) = { 2, 3 };
  __builtin_shuffle (i, i);
}

g++-4.8:
x.c:3:3: warning: statement has no effect [-Wunused-value]

gcc-4.9:
x.c:3:3: warning: value computed is not used [-Wunused-value]

g++-4.9: nothing :-(
We do warn for i+i, but not for (i+i) (again this is missing only in C++).