makedepend - create dependencies in makefiles
makedepend [-Dname=def] [-Dname] [-Iincludedir] [-Yincludedir] [-a]
[-fmakefile] [-oobjsuffix] [-pobjprefix] [-sstring] [-wwidth] [-v] [-m] [--
otheroptions --] sourcefile ...
Makedepend 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".
Include directory. This option tells makedepend to prepend inclu-
dedir to its list of directories to search when it encounters a
#include directive. By default, makedepend only searches the stan-
dard include directories (usually /usr/include and possibly a
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
Filename. This allows you to specify an alternate makefile in which
makedepend can place its output.
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
Object file prefix. The prefix is prepended to the name of the
object file. This is usually used to designate a different direc-
tory for the object file. The default is the empty string.
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 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 com-
piler arguments that might normally be found in a CFLAGS make macro
(see the EXAMPLE section below). All options that makedepend recog-
nizes and appear between the pair of double hyphens are processed
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, direc-
tives 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 mak-
edepend 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 out-
put. 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 exam-
SRCS = file1.c file2.c ...
CFLAGS = -O -DHACK -I../foobar -xyz
makedepend -- $(CFLAGS) -- $(SRCS)
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 appear-
ing 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
encounter's an include file that it has already parsed, it does not parse
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
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
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