compiler-warning-level-1-c4742.md

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Learn more about: Compiler Warning (Level 1) C4742	Compiler Warning (Level 1) C4742	07/22/2020	C4742	C4742	e520881d-1eeb-48b1-9df0-8017ee8ba076

Compiler Warning (Level 1) C4742

'variable' has different alignment in 'file1' and 'file2': number1 and number2

An external variable that was referenced or defined in two files has different alignment in those files.

Remarks

This warning is emitted when compiler finds that alignof for the variable in file1 differs from alignof for the variable in file2. This can be caused by using incompatible types when declaring variable in different files, or by using non-matching #pragma pack in different files.

To resolve this warning, either use the same type definition or use different names for the variables.

For more information, see pack and alignof operator.

Example

This is the first file that defines the type.

// C4742a.c
// compile with: /c
struct X {
   char x, y, z, w;
} global;

The following sample generates C4742.

// C4742b.c
// compile with: C4742a.c /W1 /GL
// C4742 expected
extern struct X {
   int a;
} global;

int main() {
   global.a = 0;
}