[Bug c++/21124] New: [4.1 regression] bogus "may be used uninitialized" warning

[reichelt at gcc dot gnu dot org]

On mainline I get some bogus warnings about uninitialized variables.
Just compile the following with "g++ -O -Wall":

==================================================
#include<valarray>

void foo(int i, std::valarray<int>& v)
{
    v += i*v;
}

void bar()
{
    std::valarray<int> v;

    for (int j=0; j<2; ++j)
        foo(0, v);
}
==================================================

The warning message is:

bug.cc: In function 'void bar()':
bug.cc:13: warning: 'i' may be used uninitialized in this function

A reduced version is here (compile with "-O -Wall"):

==================================================
struct A
{
    void foo() const;
};

struct B
{
    const int& i;
    const A& a;

    B(const int& __i, const A& __a) : i(__i), a(__a) {}
    static void bar(const B& b) { b.a.foo(); }
};

void baz()
{
    A a;

    for (int j=0; j<2; ++j)
        B::bar(B(0,a));
}
==================================================

The warning message for this case is even weirder (anonymous seems to refer
to the constant 0):

bug.cc: In function 'void baz()':
bug.cc:20: warning: '<anonymous>' may be used uninitialized in this function

Code like this compiled with -Werror will be rejected, so I'll rate
this as a rejects-valid bug.
The 4.0 branch is not affected.

-- 
           Summary: [4.1 regression] bogus "may be used uninitialized"
                    warning
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Keywords: rejects-valid, monitored
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: reichelt at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21124