makedepend - create dependencies in makefiles
makedepend [ -Dname=def ] [ -Dname ] [
-Iincludedir ] [ -Yincludedir ]
[ -a ] [ -fmakefile ] [ -include file
] [ -oobjsuffix ]
[ -pobjprefix ] [ -sstring ] [
-wwidth ] [ -v ] [ -m ]
[ -- otheroptions -- ] sourcefile ...
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.
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,
SRCS = file1.c file2.c ...
CFLAGS = -O -DHACK -I../foobar -xyz
depend:
makedepend -- $(CFLAGS) -- $(SRCS)
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.
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.
Todd Brunhoff, Tektronix, Inc. and MIT Project Athena