Bug 217200

Summary:	std::make_shared does not perform zero initialization
Product:	Base System	Reporter:	Dimitry Andric <dim>
Component:	misc	Assignee:	freebsd-bugs (Nobody) <bugs>
Status:	Closed FIXED
Severity:	Affects Some People
Priority:	---
Version:	10.3-STABLE
Hardware:	Any
OS:	Any
URL:	https://bugs.llvm.org/show_bug.cgi?id=32002

Description Dimitry Andric freebsd_committer

2017-02-18 13:59:33 UTC

From https://bugs.llvm.org/show_bug.cgi?id=32002:

On FreeBSD 10.3, the following program displays "123", but "0" is expected:

#include <memory>
#include <iostream>

int main()
{
    std::make_shared<int>(123);
    std::cout << *std::make_shared<int>();
    return 0;
}

The second std::make_shared reuses the piece of memory of the first one. But it should initialize it to zero, as if "new (ptr) int()" is called, where ptr is the address of allocated memory.

Comment 1 commit-hook freebsd_committer

2017-02-18 14:44:50 UTC

A commit references this bug:

Author: dim
Date: Sat Feb 18 14:44:14 UTC 2017
New revision: 313916
URL: https://svnweb.freebsd.org/changeset/base/313916

Log:
  Pull in r242377 from upstream libc++ trunk (by Marshall Clow):

    Make sure that __libcpp_compressed_pair_imp default-constructs its'
    members, rather than value-initializing them. Fixes PR#24137

  This ensures std::make_shared<>'s default constructor properly
  initializes to zero.

  Direct commit to stable/9 and stable/10, since stable/11 and head
  already have a newer version of libc++, including this fix.

  Reported by:	martin.beran@kernun.cz
  PR:		217200

Changes:
  stable/10/contrib/libc++/include/memory
  stable/9/contrib/libc++/include/memory