compiler-warning-level-4-c4221.md

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Learn more about: Compiler Warning (level 4) C4221	Compiler Warning (level 4) C4221	11/04/2016	C4221	C4221	8532bd68-54dc-4526-8597-f61dcb0a0129

Compiler Warning (level 4) C4221

nonstandard extension used : 'identifier' : cannot be initialized using address of automatic variable

With the default Microsoft extensions (/Ze), you can initialize an aggregate type (array, struct, or union) with the address of a local (automatic) variable.

Example

// C4221.c
// compile with: /W4
struct S
{
   int *i;
};

void func()
{
   int j;
   struct S s1 = { &j };   // C4221
}

int main()
{
}

Such initializations are invalid under ANSI compatibility (/Za).