MAKEDEPEND(1) MachTen Programmer’s Manual MAKEDEPEND(1)

NAME
makedepend - create dependencies in makefiles

SYNOPSIS
makedepend [ -Dname=def ] [ -Dname ] [ -Iincludedir ] [
-Yincludedir ] [ -a ] [ -fmakefile ] [ -oobjsuffix ] [
-pobjprefix ] [ -sstring ] [ -wwidth ] [ -v ] [ -m ] [ --
otheroptions -- ] sourcefile ...

DESCRIPTION
Makedepend reads each sourcefile in sequence and parses it
like a C-preprocessor, processing all #include, #define,
#undef, #ifdef, #ifndef, #endif, #if 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 indi-
rectly, 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 recom-
piled 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 every-
thing 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 pars-
ing 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,
SRCS = file1.c file2.c ...
CFLAGS = -O -DHACK -I../foobar -xyz
depend:
makedepend -- $(CFLAGS) -- $(SRCS)

OPTIONS
Makedepend will ignore any option that it does not under-
stand 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 makede-
pend’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 possi-
bly 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 stan-
dard 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.

-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 des-
ignate 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 on
standard output.

-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 follow-
ing 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 nor-
mally.

ALGORITHM
The approach used in this program enables it to run an
order of magnitude faster than any other "dependency gen-
erator" I have ever seen. Central to this performance are
two assumptions: that all files compiled by a single make-
file 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, main-
taining 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 prepro-
cessor takes. But on subsequent files, if it encounter’s
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.