makedepend - create dependencies in makefiles
makedepend [ -Dname=def ] [ -Dname ] [ -Iincludedir ] [ -Yincludedir ]
[ -a ] [ -fmakefile ] [ -include file ] [ -oobjsuffix ] [ -pobjprefix ]
[ -sstring ] [ -wwidth ] [ -v ] [ -m ] [ -- otheroptions -- ]
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
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
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
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’’.
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
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
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.
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.
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.
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.
Starting string delimiter. This option permits you to specify a
different string for makedepend to look for in the makefile.
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
-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
-- 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
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