compiler-warning-c4957.md

description	title	ms.date	f1_keywords	helpviewer_keywords	ms.assetid
Learn more about: Compiler Warning C4957	Compiler Warning C4957	11/04/2016	C4957	C4957	a18c52d4-23e2-44f1-b4b5-f7fa5a7f3987

Compiler Warning C4957

'cast' : explicit cast from 'cast_from' to 'cast_to' is not verifiable

Remarks

A cast will result in an unverifiable image.

Some casts are safe (for example, a static_cast that triggers user-defined conversions and a const_cast). A safe_cast is guaranteed to produce verifiable code.

For more information, see Pure and Verifiable Code (C++/CLI).

The /clr:safe compiler option is deprecated in Visual Studio 2015 and unsupported in Visual Studio 2017.

This warning is issued as an error and can be disabled with the warning pragma or the /wd compiler option.

Example

The following sample generates C4957:

// C4957.cpp
// compile with: /clr:safe
// #pragma warning( disable : 4957 )
using namespace System;
int main() {
   Object ^ o = "Hello, World!";
   String ^ s = static_cast<String^>(o);   // C4957
   String ^ s2 = safe_cast<String^>(o);   // OK
}