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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.

SEE ALSO
     cc(1), make(1)

BUGS
     makedepend parses, but does not currently evaluate, the SVR4
     #predicate(token-list) preprocessor expression; such expres-
     sions 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 mak-
     edepend arrives at a list of dependencies for a file, it  is
     cast in concrete.

AUTHOR
     Todd Brunhoff, Tektronix, Inc. and MIT Project Athena

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