Re: std::copy unsafe error
On Tue, 24 Jun 2014 15:04:35 -0500, Christopher Pisz
<nospam@notanaddress.com> wrote:
On 6/24/2014 12:14 PM, Victor Bazarov wrote:
On 6/24/2014 12:41 PM, Christopher Pisz wrote:
I am getting an error from std::copy_impl about this being unsafe. Is
there an alternative I can use? Or am I using it incorrectly here? I am
not sure why this would be "unsafe."
void Foo(const std::wstring & text)
{
// Double NULL required at end
wchar_t * buffer = new wchar_t[fullyQualifiedPath.size() + 2];
std::copy(fullyQualifiedPath.begin(), fullyQualifiedPath.end(),
buffer);
buffer[fullyQualifiedPath.size() ] = L'\0';
buffer[fullyQualifiedPath.size() + 1] = L'\0';
// SNIP
}
Not enough information. How is 'fullyQualifiedPath' declared? Also,
consider that you actually don't need to do the .size()] = 0 if you
zero-initialize it using the parentheses:
... buffer = new ... + 2]();
What's "std::copy_impl" and how are you "getting an error" from it about
your code "being unsafe"? Be more verbose. Is this a compiler error?
Then provide the compiler output. Is it a run-time error? Then provide
the output of your program.
Is this your first day in c.l.c++?
V
Full listing:
#include <string>
#include <algorithm>
void Foo(const std::wstring & text)
{
// Double NULL required at end
wchar_t * buffer = new wchar_t[text.size() + 2];
std::copy(text.begin(), text.end(), buffer);
buffer[text.size() ] = L'\0';
buffer[text.size() + 1] = L'\0';
// SNIP
}
int main()
{
std::wstring text = L"blahdedeblahblah";
return 0;
}
MSVC11.0 gives compiler error:
Error 1 error C4996: 'std::_Copy_impl': Function call with parameters
that may be unsafe - this call relies on the caller to check that the
passed values are correct. To disable this warning, use
-D_SCL_SECURE_NO_WARNINGS. See documentation on how to use Visual C++
'Checked Iterators' c:\program files (x86)\microsoft visual studio
11.0\vc\include\xutility 2176 Test
I am asking why the compiler believes it to be unsafe, if it is indeed
unsafe, or if there an alternative way I should be using.
I imagine std::copy_impl is microsoft's implementation of std::copy, but
who knows.
Your use of MSVC11.0 is somewhat ambiguous to me. Do you mean Visual
Studio 2012? This is internally versioned 11.0 but the compiler itself
is version 17.00.x.x.
I compiled your sample in Visual Studio 2010, compiler version
16.00.40219.01 and it generates a WARNING, not an error. Perhaps you
have turned on /WX "Treat Warnings as errors"? But VS2010 emits error
C2220 if that's the case and C4996 remains a warning. Did you omit
that line from your post?
In VS2010 this C4996 warning is not emitted in Release mode builds of
your example and this behavior is documented in MSDN.
This is Microsoft's way of trying to catch/help newbs who might
otherwise build buffer overflows into their code. What this warning
means is the compiler will check your iterators in debug mode to make
sure they don't overrun the buffer you have allocated. If you are
confident your code is correct you can suppress this warning by
writing #define _SCL_SECURE_NO_WARNINGS and your code will still check
the iterators for overflows in Debug mode and you will get undefined
behavior when executing in release mode in the event of an overflow.