Compiler Warning (level 1) C4269


The new home for Visual Studio documentation is Visual Studio 2017 Documentation on

The latest version of this topic can be found at Compiler Warning (level 1) C4269.

identifier' : 'const' automatic data initialized with compiler generated default constructor produces unreliable results

A const automatic instance of a non-trivial class is initialized with a compiler-generated default constructor.

// C4269.cpp  
// compile with: /c /LD /W1  
class X {  
   int m_data;  
void g() {  
   const X x1;   // C4269  

Since this instance of the class is generated on the stack, the initial value of m_data can be anything. Also, since it is a const instance, the value of m_data can never be changed.