http://llvm.org/bugs/show_bug.cgi?id=16238
Bug ID: 16238
Summary: Modifying a deque from emplace_back produces incorrect
results
Product: libc++
Version: unspecified
Hardware: PC
OS: All
Status: NEW
Severity: normal
Priority: P
Component: All Bugs
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
>From my skimming into the standard, nothing specifically seems to prohibit
modifying a `std::deque` from inside `emplace_back`. Take this snippet for
example:
#include <iostream>
#include <deque>
#include <string>
using namespace std;
struct foo
{
string m_marker;
foo(deque<foo>& into, const string& marker, bool createInner = true)
: m_marker(marker)
{
if (createInner)
{
cout << "Marker is " << m_marker << endl;
into.emplace_back(into, "my other marker", false);
cout << "Marker is now " << m_marker << endl;
}
}
};
int main()
{
deque<foo> foos;
foos.emplace_back(foos, "my initial marker");
cout << "There are " << foos.size() << " items in the deque:" << endl;
for (foo& f : foos)
cout << f.m_marker << endl;
}
(listing also at http://stackoverflow.com/q/16955265/)
I would expect this as the result:
> Marker is my initial marker
> Marker is now my initial marker
> There are 2 items in the deque:
> my initial marker
> my other marker
However, this is what I get:
> Marker is my initial marker
> Marker is now my other marker
> There are 2 items in the deque:
> my other marker
>
It looks like calling `emplace_back` from within a constructor itself called
with `emplace_back` causes the deque to overwrite the first item with the
second.
I couldn't find anything that specifically prohibits modifying the container
from `emplace` methods in N3337, although I can see why this could be a
problem.
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