The
makedepend
program reads each
sourcefile
in sequence and parses it like a C-preprocessor,
processing all
#include,#define,#undef,#ifdef,#ifndef,#endif,#if,#elif
and
#else
directives so that it can correctly tell which
#include,
directives would be used in a compilation.
Any
#include,
directives can reference files having other
#include
directives, and parsing will occur in these files as well.
Every file that a
sourcefile
includes,
directly or indirectly,
is what
makedepend
calls a dependency.
These dependencies are then written to a
makefile
in such a way that
make(1)
will know which object files must be recompiled when a dependency has changed.
By default,
makedepend
places its output in the file named
makefile
if it exists, otherwise
Makefile.
An alternate makefile may be specified with the
-f
option.
It first searches the makefile for
the line
# DO NOT DELETE THIS LINE -- make depend depends on it.
or one provided with the
-s
option,
as a delimiter for the dependency output.
If it finds it, it will delete everything
following this to the end of the makefile
and put the output after this line.
If it doesn't find it, the program
will append the string to the end of the makefile
and place the output following that.
For each
sourcefile
appearing on the command line,
makedepend
puts lines in the makefile of the form
sourcefile.o: dfile ...
Where sourcefile.o is the name from the command
line with its suffix replaced with ``.o'',
and dfile is a dependency discovered in a
#include
directive while parsing
sourcefile
or one of the files it included.
EXAMPLE
Normally,
makedepend
will be used in a makefile target so that typing ``make depend'' will
bring the dependencies up to date for the makefile.
For example,
The program
will ignore any option that it does not understand so that you may use
the same arguments that you would for
cc(1).
-Dname=def or -Dname
Define.
This places a definition for
name
in
makedepend's
symbol table.
Without
=def
the symbol becomes defined as ``1''.
-Iincludedir
Include directory.
This option tells
makedepend
to prepend
includedir
to its list of directories to search when it encounters
a
#include
directive.
By default,
makedepend
only searches the standard include directories (usually /usr/include
and possibly a compiler-dependent directory).
-Yincludedir
Replace all of the standard include directories with the single specified
include directory; you can omit the
includedir
to simply prevent searching the standard include directories.
-a
Append the dependencies to the end of the file instead of replacing them.
-fmakefile
Filename.
This allows you to specify an alternate makefile in which
makedepend
can place its output.
Specifying ``-'' as the file name (i.e., -f-) sends the
output to standard output instead of modifying an existing file.
-include file
Process file as input, and include all the resulting output
before processing the regular input file. This has the same
affect as if the specified file is an include statement that
appears before the very first line of the regular input file.
-oobjsuffix
Object file suffix.
Some systems may have object files whose suffix is something other
than ``.o''.
This option allows you to specify another suffix, such as
``.b'' with
-o.b
or ``:obj''
with
-o:obj
and so forth.
-pobjprefix
Object file prefix.
The prefix is prepended to the name of the object file. This is
usually used to designate a different directory for the object file.
The default is the empty string.
-sstring
Starting string delimiter.
This option permits you to specify
a different string for
makedepend
to look for in the makefile.
-wwidth
Line width.
Normally,
makedepend
will ensure that every output line that it writes will be no wider than
78 characters for the sake of readability.
This option enables you to change this width.
-v
Verbose operation.
This option causes
makedepend
to emit the list of files included by each input file.
-m
Warn about multiple inclusion.
This option causes
makedepend
to produce a warning if any input file includes another file more than
once. In previous versions of
makedepend
this was the default behavior; the default has been changed to better
match the behavior of the C compiler, which does not consider multiple
inclusion to be an error. This option is provided for backward
compatibility, and to aid in debugging problems related to multiple
inclusion.
-- options --
If
makedepend
encounters a double hyphen (--) in the argument list,
then any unrecognized argument following it
will be silently ignored; a second double hyphen terminates this
special treatment.
In this way,
makedepend
can be made to safely ignore esoteric compiler arguments that might
normally be found in a CFLAGS
make
macro (see the
EXAMPLE
section above).
All options that
makedepend
recognizes and appear between the pair of double hyphens
are processed normally.
ALGORITHM
The approach used in this program enables it to run an order of magnitude
faster than any other ``dependency generator'' I have ever seen.
Central to this performance are two assumptions:
that all files compiled by a single
makefile will be compiled with roughly the same
-I
and
-D
options;
and that most files in a single directory will include largely the
same files.
Given these assumptions,
makedepend
expects to be called once for each makefile, with
all source files that are maintained by the
makefile appearing on the command line.
It parses each source and include
file exactly once, maintaining an internal symbol table
for each.
Thus, the first file on the command line will take an amount of time
proportional to the amount of time that a normal C preprocessor takes.
But on subsequent files, if it encounters an include file
that it has already parsed, it does not parse it again.
For example,
imagine you are compiling two files,
file1.c
and
file2.c,
they each include the header file
header.h,
and the file
header.h
in turn includes the files
def1.h
and
def2.h.
When you run the command
makedepend file1.c file2.c
makedepend
will parse
file1.c
and consequently,
header.h
and then
def1.h
and
def2.h.
It then decides that the dependencies for this file are
file1.o: header.h def1.h def2.h
But when the program parses
file2.c
and discovers that it, too, includes
header.h,
it does not parse the file,
but simply adds
header.h,def1.h
and
def2.h
to the list of dependencies for
file2.o.
makedepend
parses, but does not currently evaluate, the SVR4 #predicate(token-list)
preprocessor expression; such expressions are simply assumed to be true.
This may cause the wrong
#include
directives to be evaluated.
Imagine you are parsing two files,
say
file1.c
and
file2.c,
each includes the file
def.h.
The list of files that
def.h
includes might truly be different when
def.h
is included by
file1.c
than when it is included by
file2.c.
But once
makedepend
arrives at a list of dependencies for a file,
it is cast in concrete.
AUTHOR
Todd Brunhoff, Tektronix, Inc. and MIT Project Athena
