Ubuntu Manpage: makedepend - create dependencies in makefiles

NAME

       makedepend - create dependencies in makefiles

SYNOPSIS

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

DESCRIPTION

       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 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

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''.

-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
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. Specifying ``-'' as the file name (i.e., -f-) sends the output to
standard output instead of modifying an existing file.

-include 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.

-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 designate 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.

-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 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
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 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.

BUGS

       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.

AUTHOR

       Todd Brunhoff, Tektronix, Inc. and MIT Project Athena