ARM Compiler toolchain v4.1 for µVision Using the Compiler

Compiler Features
4.23 PreCompiled Header (PCH) file processing and the header stop point
The PCH file contains a snapshot of all the code that precedes a header stop point. Typically,
the header stop point is the first token in the primary source file that does not belong to a
preprocessing directive. In the following example, the header stop point is int and the PCH file
contains a snapshot that reflects the inclusion of xxx.h and yyy.h:
#include "xxx.h"
#include "yyy.h"
int i;
The header stop point can be manually specified with #pragma hdrstop. If used, this pragma must
be placed before the first token that does not belong to a preprocessing directive. In this
example, it must be placed before int, as follows:
#include "xxx.h"
#include "yyy.h"
#pragma hdrstop
int i;
If a #if block encloses the first non-preprocessor token or #pragma hdrstop, the header stop point
is the outermost enclosing #if. For example:
#include "xxx.h"
#ifndef YYY_H
#define YYY_H 1
#include "yyy.h"
#endif
#if TEST /* Header stop point lies immediately before #if TEST */
int i;
#endif
In this example, the first token that does not belong to a preprocessing directive is int, but the
header stop point is the start of the #if block containing it. The PCH file reflects the inclusion
of xxx.h and, conditionally, the definition of YYY_H and inclusion of yyy.h. It does not contain the
state produced by #if TEST.
4.23.1 See also
Tasks
• Selectively applying PreCompiled Header (PCH) file processing on page 4-37
• Selectively applying PreCompiled Header (PCH) file processing on page 4-37
• Suppressing PreCompiled Header (PCH) file processing on page 4-38.
Concepts
• PreCompiled Header (PCH) files on page 4-29
• Automatic PreCompiled Header (PCH) file processing on page 4-30
• PreCompiled Header (PCH) file creation requirements on page 4-32
• PreCompiled Header (PCH) file creation requirements on page 4-32
• Performance issues with PreCompiled Header (PCH) files on page 4-40.
Reference
Compiler Reference:
• #pragma hdrstop on page 5-52
• --pch on page 3-75
• --pch_dir=dir on page 3-75.
ARM DUI 0375C Copyright © 2007-2008, 2011 ARM. All rights reserved. 4-31
ID061811
Non-Confidential