X Version 11 (Release 5)

makedepend(XS)

makedepend -- create dependencies in makefiles

Syntax

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, 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(CP) 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

makedepend will ignore any option that it does not understand so that you may use the same arguments that you would for cc(CP).

-Dname=def: Define. This places a definition for name in makedepend's symbol table.
-Dname: Define. This places a definition for name in makedepend's symbol table. 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" by using -o.b or ":obj" by using -o:obj and so forth.
-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 specify 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 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 other "dependency generators." 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 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.

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 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.