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 pars-
ing 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 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 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,
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
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 direc-
tories (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.

-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 desig-
nate 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 mak-
edepend 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 com-
patibility, 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, mak-
edepend 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 assump-
tions: 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 main-
tained by the makefile appearing on the command line. It
parses each source and include file exactly once, maintain-
ing 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 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 dependen-
cies 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 sim-
ply adds header.h, def1.h and def2.h to the list of depen-
dencies for file2.o.