Given the following source code

class K
{
public:
    K * copy();
};

class FunctionExpr
{
public:
    FunctionExpr( const FunctionExpr & );

private:
    K * args;
};

FunctionExpr::FunctionExpr(const FunctionExpr& expr)
        : args(expr.args ? args->copy() : 0)
{
}

then trunk gcc can't detect the read of uninit memory for args->copy.

$ ~/gcc/results/bin/gcc -c -g -O2 -Wall -Wextra -pedantic bug189.cc
$

Here is clang doing the right thing:

$ ~/llvm/results/bin/clang++ -c -g -O2 -Wall -Wextra -pedantic bug189.cc
bug189.cc:18:28: warning: field 'args' is uninitialized when used here
      [-Wuninitialized]
        : args(expr.args ? args->copy() : 0)
                           ^
1 warning generated.
$