Was this page helpful?
Your feedback about this content is important. Let us know what you think.
Additional feedback?
1500 characters remaining
Compiler Warning (Level 1) C4742
Collapse the table of content
Expand the table of content

Compiler Warning (Level 1) C4742

Error Message

'var' has different alignment in 'file1' and 'file2': number and number

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


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;

Community Additions

© 2015 Microsoft