MAKEDEPEND(1) MAKEDEPEND(1)
NAME
makedepend - create dependencies in makefiles
SYNOPSIS
makedepend [ -Dname=def ] [ -Dname ] [ -Iincludedir ] [ -fmakefile ] [
-oobjsuffix ] [ -sstring ] [ -wwidth ] [ - - 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, 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.
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 exam-
ple,
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 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 /usr/include.
-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.
-sstring
Starting string delimiter. This option permits you to specify a dif-
ferent 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.
- - 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 argu-
ments 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 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
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.
SEE ALSO
cc(1), make(1)
BUGS
If you do not have the source for cpp, the Berkeley C preprocessor, then
makedepend will be compiled in such a way that all #if directives will
evaluate to "true" regardless of their actual value. This may cause the
wrong #include directives to be evaluated. Makedepend should simply have
its own parser written for #if expressions.
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 dif-
ferent 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.
AUTHOR
Todd Brunhoff, Tektronix, Inc. and MIT Project Athena