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From: "dcb314 at hotmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/65301] New: gcc can't detect some uninit reads in ctor init lists
Date: Tue, 03 Mar 2015 15:55:00 -0000
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X-Bugzilla-Component: c++
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65301

            Bug ID: 65301
           Summary: gcc can't detect some uninit reads in ctor init lists
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dcb314 at hotmail dot com

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.
$