Info Catalog make: Utilities in Makefiles make: Makefile Conventions make: DESTDIR

make: Command Variables

 
 16.3 Variables for Specifying Commands
 ======================================
 
 Makefiles should provide variables for overriding certain commands,
 options, and so on.
 
    In particular, you should run most utility programs via variables.
 Thus, if you use Bison, have a variable named 'BISON' whose default
 value is set with 'BISON = bison', and refer to it with '$(BISON)'
 whenever you need to use Bison.
 
    File management utilities such as 'ln', 'rm', 'mv', and so on, need
 not be referred to through variables in this way, since users don't need
 to replace them with other programs.
 
    Each program-name variable should come with an options variable that
 is used to supply options to the program.  Append 'FLAGS' to the
 program-name variable name to get the options variable name--for
 example, 'BISONFLAGS'.  (The names 'CFLAGS' for the C compiler, 'YFLAGS'
 for yacc, and 'LFLAGS' for lex, are exceptions to this rule, but we keep
 them because they are standard.)  Use 'CPPFLAGS' in any compilation
 command that runs the preprocessor, and use 'LDFLAGS' in any compilation
 command that does linking as well as in any direct use of 'ld'.
 
    If there are C compiler options that _must_ be used for proper
 compilation of certain files, do not include them in 'CFLAGS'.  Users
 expect to be able to specify 'CFLAGS' freely themselves.  Instead,
 arrange to pass the necessary options to the C compiler independently of
 'CFLAGS', by writing them explicitly in the compilation commands or by
 defining an implicit rule, like this:
 
      CFLAGS = -g
      ALL_CFLAGS = -I. $(CFLAGS)
      .c.o:
              $(CC) -c $(CPPFLAGS) $(ALL_CFLAGS) $<
 
    Do include the '-g' option in 'CFLAGS', because that is not
 _required_ for proper compilation.  You can consider it a default that
 is only recommended.  If the package is set up so that it is compiled
 with GCC by default, then you might as well include '-O' in the default
 value of 'CFLAGS' as well.
 
    Put 'CFLAGS' last in the compilation command, after other variables
 containing compiler options, so the user can use 'CFLAGS' to override
 the others.
 
    'CFLAGS' should be used in every invocation of the C compiler, both
 those which do compilation and those which do linking.
 
    Every Makefile should define the variable 'INSTALL', which is the
 basic command for installing a file into the system.
 
    Every Makefile should also define the variables 'INSTALL_PROGRAM' and
 'INSTALL_DATA'.  (The default for 'INSTALL_PROGRAM' should be
 '$(INSTALL)'; the default for 'INSTALL_DATA' should be '${INSTALL} -m
 644'.)  Then it should use those variables as the commands for actual
 installation, for executables and non-executables respectively.  Minimal
 use of these variables is as follows:
 
      $(INSTALL_PROGRAM) foo $(bindir)/foo
      $(INSTALL_DATA) libfoo.a $(libdir)/libfoo.a
 
    However, it is preferable to support a 'DESTDIR' prefix on the target
 files, as explained in the next section.
 
    It is acceptable, but not required, to install multiple files in one
 command, with the final argument being a directory, as in:
 
      $(INSTALL_PROGRAM) foo bar baz $(bindir)
 

Info Catalog make: Utilities in Makefiles make: Makefile Conventions make: DESTDIR