MSVC Compiler Error C4315 - No Documentation Found

Question

When compiling my app today, I encountered this warning (the code, I think, is irrelevant):

warning C4315: 'MyClass' : 'this' pointer for member 'MyClass::my_data_' may not be aligned 8 as expected by the constructor

I am not able to find any documentation about this warning, in either the online help, my locally-installed help, or via a google search. I did find one link on a MS forum:

No documentation for compiler warning C4315

But no information about the error itself.

Do you have any information about this error? I'm trying to fogure out how to fix it.

Answer 1

I'd look for something (buried in a header?) changing the structure packing from the default.

The warning seems to be saying that whatever type MyClass::my_data_ is expects to be 8-byte aligned, but it's not being placed at that alignment inside MyClass.

Search for #pragma pack(some-number) directives that aren't reset with a #pragma pack().

Using #pragma pack(show) would probably be helpful, too.