Header file checker
iwyu is a tool for deciding which #includes are needed, or not.
Including the right files, and no more, can speed up builds.
It also helps to show the dependencies of a file.
iwyu uses clang to create an AST for the code.
A sample call and its output.
iwyu -I. -Xiwyu --no_comments -Xiwyu --pch_in_code -Xiwyu --mapping_file=neomutt.imp thread.c
thread.c should remove these lines:
- #include "globals.h"
The full include-list for thread.c:
#include "config.h"
#include "thread.h"
#include <limits.h>
#include <stdlib.h>
#include <time.h>
#include "body.h"
#include "header.h"
#include "mutt/mutt.h"
#include "sort.h"
Common options used are:
| Option | Description | Notes |
|---|---|---|
-I. |
Add an include dir .
|
Passed to clang |
-DSYMBOL |
Define a SYMBOL | Passed to clang |
-Xiwyu --no_comments |
Don’t add notes to the output | IWYU option |
-Xiwyu --pch_in_code |
The file has an important header first | IWYU option |
-Xiwyu --mapping_file=FILE |
Use this lookup file | IWYU option |
It’s hard for iwyu to work out which header files the developers think are important. For example, in NeoMutt, you can replace lots of library headers:
#include "mutt/message.h"
#include "mutt/address.h"
#include "mutt/rfc2047.h"
#include "mutt/mapping.h"
#include "mutt/hash.h"
with one helper header
#include "mutt/mutt.h"
The mapping file also provides fixes for some header files in glibc that cause confusion. It looks like this:
# Include one library header rather than the individual headers.
{ include: [ '@"mutt/.*"', private, '"mutt/mutt.h"', public ] },
{ include: [ '@"conn/.*"', private, '"conn/conn.h"', public ] },
