Make/Implicit-Variables
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10.3 Variables Used by Implicit Rules
The recipes in built-in implicit rules make liberal use of certain
predefined variables. You can alter the values of 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 ‘--no-builtin-variables
’ option.
For example, the recipe 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
programs (like 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
with spaces.
The following tables describe of some of the more commonly-used predefined
variables. This list is not exhaustive, and the default values shown here may
not be what make
selects for your environment. To see the
complete list of predefined variables for your instance of GNU make
you
can run ‘make -p
’ in a directory with no makefiles.
Here is a table of some of the more common variables used as names of programs in built-in rules:
AR
Archive-maintaining program; default ‘
ar
’.AS
Program for compiling assembly files; default ‘
as
’.CC
Program for compiling C programs; default ‘
cc
’.CXX
Program for compiling C++ programs; default ‘
g++
’.CPP
Program for running the C preprocessor, with results to standard output; default ‘
$(CC) -E
’.FC
Program for compiling or preprocessing Fortran and Ratfor programs; default ‘
f77
’.M2C
Program to use to compile Modula-2 source code; default ‘
m2c
’.PC
Program for compiling Pascal programs; default ‘
pc
’.CO
Program for extracting a file from RCS; default ‘
co
’.GET
Program for extracting a file from SCCS; default ‘
get
’.LEX
Program to use to turn Lex grammars into source code; default ‘
lex
’.YACC
Program to use to turn Yacc grammars into source code; default ‘
yacc
’.LINT
Program to use to run lint on source code; default ‘
lint
’.MAKEINFO
Program to convert a Texinfo source file into an Info file; default ‘
makeinfo
’.TEX
Program to make TeX DVI files from TeX source; default ‘
tex
’.TEXI2DVI
Program to make TeX DVI files from Texinfo source; default ‘
texi2dvi
’.WEAVE
Program to translate Web into TeX; default ‘
weave
’.CWEAVE
Program to translate C Web into TeX; default ‘
cweave
’.TANGLE
Program to translate Web into Pascal; default ‘
tangle
’.CTANGLE
Program to translate C Web into C; default ‘
ctangle
’.RM
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.
ARFLAGS
Flags to give the archive-maintaining program; default ‘
rv
’.ASFLAGS
Extra flags to give to the assembler (when explicitly invoked on a ‘
.s
’ or ‘.S
’ file).CFLAGS
Extra flags to give to the C compiler.
CXXFLAGS
Extra flags to give to the C++ compiler.
COFLAGS
Extra flags to give to the RCS
co
program.CPPFLAGS
Extra flags to give to the C preprocessor and programs that use it (the C and Fortran compilers).
FFLAGS
Extra flags to give to the Fortran compiler.
GFLAGS
Extra flags to give to the SCCS
get
program.LDFLAGS
Extra flags to give to compilers when they are supposed to invoke the linker, ‘
ld
’, such as-L
. Libraries (-lfoo
) should be added to theLDLIBS
variable instead.LDLIBS
Library flags or names given to compilers when they are supposed to invoke the linker, ‘
ld
’.LOADLIBES
is a deprecated (but still supported) alternative toLDLIBS
. Non-library linker flags, such as-L
, should go in theLDFLAGS
variable.LFLAGS
Extra flags to give to Lex.
YFLAGS
Extra flags to give to Yacc.
PFLAGS
Extra flags to give to the Pascal compiler.
RFLAGS
Extra flags to give to the Fortran compiler for Ratfor programs.
LINTFLAGS
Extra flags to give to lint.
Next: Chained Rules, Previous: Catalogue of Rules, Up: Implicit Rules [Contents][Index]