The header stop point must appear at file scope. It must not be within an unclosed scope established by a header file. For example, a PCH file is not created in this case:

// xxx.h
class A
{
    // xxx.c
    #include "xxx.h"
    int i;
}; 

The header stop point must not be inside a declaration that is started within a header file. Also, in C++, it must not be part of a declaration list of a linkage specification. For example, in the following case the header stop point is int, but because it is not the start of a new declaration, no PCH file is created:

// yyy.h
static
// yyy.c
#include "yyy.h"
int i; 

The header stop point must not be inside a #if block or a #define that is started within a header file.

The processing that precedes the header stop point must not have produced any errors.

No references to predefined macros __DATE__ or __TIME__ must appear.

No instances of the #line preprocessing directive must appear.

#pragma no_pch must not appear.

The code preceding the header stop point must have introduced a sufficient number of declarations to justify the overhead associated with precompiled headers.