(make.info.gz) Makefile Basics

Info Catalog

(make.info.gz) Makefile Conventions

(make.info.gz) Utilities in Makefiles

 
 14.1 General Conventions for Makefiles
 ======================================
 
 Every Makefile should contain this line:
 
      SHELL = /bin/sh
 
 to avoid trouble on systems where the `SHELL' variable might be
 inherited from the environment.  (This is never a problem with GNU
 `make'.)
 
    Different `make' programs have incompatible suffix lists and
 implicit rules, and this sometimes creates confusion or misbehavior.  So
 it is a good idea to set the suffix list explicitly using only the
 suffixes you need in the particular Makefile, like this:
 
      .SUFFIXES:
      .SUFFIXES: .c .o
 
 The first line clears out the suffix list, the second introduces all
 suffixes which may be subject to implicit rules in this Makefile.
 
    Don't assume that `.' is in the path for command execution.  When
 you need to run programs that are a part of your package during the
 make, please make sure that it uses `./' if the program is built as
 part of the make or `$(srcdir)/' if the file is an unchanging part of
 the source code.  Without one of these prefixes, the current search
 path is used.
 
    The distinction between `./' (the "build directory") and
 `$(srcdir)/' (the "source directory") is important because users can
 build in a separate directory using the `--srcdir' option to
 `configure'.  A rule of the form:
 
      foo.1 : foo.man sedscript
              sed -e sedscript foo.man > foo.1
 
 will fail when the build directory is not the source directory, because
 `foo.man' and `sedscript' are in the source directory.
 
    When using GNU `make', relying on `VPATH' to find the source file
 will work in the case where there is a single dependency file, since
 the `make' automatic variable `$<' will represent the source file
 wherever it is.  (Many versions of `make' set `$<' only in implicit
 rules.)  A Makefile target like
 
      foo.o : bar.c
              $(CC) -I. -I$(srcdir) $(CFLAGS) -c bar.c -o foo.o
 
 should instead be written as
 
      foo.o : bar.c
              $(CC) -I. -I$(srcdir) $(CFLAGS) -c $< -o $@
 
 in order to allow `VPATH' to work correctly.  When the target has
 multiple dependencies, using an explicit `$(srcdir)' is the easiest way
 to make the rule work well.  For example, the target above for `foo.1'
 is best written as:
 
      foo.1 : foo.man sedscript
              sed -e $(srcdir)/sedscript $(srcdir)/foo.man > $@
 
    GNU distributions usually contain some files which are not source
 files--for example, Info files, and the output from Autoconf, Automake,
 Bison or Flex.  Since these files normally appear in the source
 directory, they should always appear in the source directory, not in the
 build directory.  So Makefile rules to update them should put the
 updated files in the source directory.
 
    However, if a file does not appear in the distribution, then the
 Makefile should not put it in the source directory, because building a
 program in ordinary circumstances should not modify the source directory
 in any way.
 
    Try to make the build and installation targets, at least (and all
 their subtargets) work correctly with a parallel `make'.
 

Info Catalog

(make.info.gz) Makefile Conventions

(make.info.gz) Utilities in Makefiles