10.3 Variables Used by Implicit Rules
The commands in built-in implicit rules make liberal use of certain
predefined variables. You can alter these variables in the makefile,
with arguments to
make, or in the environment to alter how the
implicit rules work without redefining the rules themselves. You can
cancel all variables used by implicit rules with the `-R' or
For example, the command used to compile a C source file actually says
`$(CC) -c $(CFLAGS) $(CPPFLAGS)'. The default values of the variables
used are `cc' and nothing, resulting in the command `cc -c'. By
redefining `CC' to `ncc', you could cause `ncc' to be
used for all C compilations performed by the implicit rule. By redefining
`CFLAGS' to be `-g', you could pass the `-g' option to
each compilation. All implicit rules that do C compilation use
`$(CC)' to get the program name for the compiler and all
include `$(CFLAGS)' among the arguments given to the compiler.
The variables used in implicit rules fall into two classes: those that are
names of programs (like
CC) and those that contain arguments for the
CFLAGS). (The "name of a program" may also contain
some command arguments, but it must start with an actual executable program
name.) If a variable value contains more than one argument, separate them
Here is a table of variables used as names of programs in built-in rules:
Archive-maintaining program; default `ar'.
Program for doing assembly; default `as'.
Program for compiling C programs; default `cc'.
Program for compiling C++ programs; default `g++'.
Program for extracting a file from RCS; default `co'.
Program for running the C preprocessor, with results to standard output;
default `$(CC) -E'.
Program for compiling or preprocessing Fortran and Ratfor programs;
Program for extracting a file from SCCS; default `get'.
Program to use to turn Lex grammars into C programs or Ratfor programs;
Program for compiling Pascal programs; default `pc'.
Program to use to turn Yacc grammars into C programs; default `yacc'.
Program to use to turn Yacc grammars into Ratfor
programs; default `yacc -r'.
Program to convert a Texinfo source file into an Info file; default
Program to make TeX DVI files from TeX source;
Program to make TeX DVI files from Texinfo source;
Program to translate Web into TeX; default `weave'.
Program to translate C Web into TeX; default `cweave'.
Program to translate Web into Pascal; default `tangle'.
Program to translate C Web into C; default `ctangle'.
Command to remove a file; default `rm -f'.
Here is a table of variables whose values are additional arguments for the
programs above. The default values for all of these is the empty
string, unless otherwise noted.
Flags to give the archive-maintaining program; default `rv'.
Extra flags to give to the assembler (when explicitly
invoked on a `.s' or `.S' file).
Extra flags to give to the C compiler.
Extra flags to give to the C++ compiler.
Extra flags to give to the RCS
Extra flags to give to the C preprocessor and programs
that use it (the C and Fortran compilers).
Extra flags to give to the Fortran compiler.
Extra flags to give to the SCCS
Extra flags to give to compilers when they are
supposed to invoke the linker, `ld'.
Extra flags to give to Lex.
Extra flags to give to the Pascal compiler.
Extra flags to give to the Fortran compiler for Ratfor programs.
Extra flags to give to Yacc.