makefile_gnu

Supported GNU make command options

clearmake –C gnu supports most of the single-character and long-form spellings of GNU make command options, as follows:

–b

Considers siblings when determining whether to rebuild or reuse.

– –directory=dir

Change to the specified directory before reading the makefiles.

–d – –debug

Prints debugging information in addition to normal processing messages.

–e – –environment-override

Gives variables taken from the environment precedence over variables from makefiles.

–f file – –file=file – –makefile=file

Reads file as a makefile.

–I dir

Specifies a directory dir to search for included makefiles (this is equivalent to –include-dir.

–i – –ignore-errors

Ignores all errors in commands executed to remake files.

– –include-dir=dir

Specifies a directory in which to search for included makefiles (this is equivalent to –I

–k – –keep-going

Continues as much as possible after an error.

– –no-builtin-variables

Eliminate use of built-in, rule-specific variables.

– –-no-print-directory

Disables printing of the working directory under –w.

–n – –just-print – –dry-run – –-recon

Prints the commands that would be executed, but does not execute them.

–p – –print-data-base

Prints the database (rules and variable values) that results from reading the makefiles, then executes as usual or as otherwise specified.

–q – –question

Question mode. Does not run any commands or print anything. Returns an exit status of 0 if the specified targets are already up to date, or 1 if any remaking is required.

–r – –no-builtin-rules

Eliminates use of the built-in implicit rules.

–s – –silent – –quiet

Silent operation. Does not print the commands as they are executed.

– –warn-undefined-variables

Issues a warning whenever a reference to an undefined variable is found. Null warnings for VPATH and SHELL are suppressed by default; null warnings for these can be displayed using the clearmake options –v or –d.

–w – –print-directory

Prints a message containing the working directory both before and after executing the makefile.

Unsupported GNU make command-line options

The following options are not supported:

• -m
• -C dir
• -h --help
• -j [jobs] --jobs[=jobs]
• -l [load] --load-average[=load] --max-load[=load]
• -o file --old-file=file --assume-old=file
• -R (this is supported as –b)
• -S --no-keep-going --stop
• -t --touch
• -v --version
• -W file --what-if=file --new-file=file --assume-new=file

Supported GNU make features

The following features are enabled with –C gnu (see the GNU make documentation):

• Conditional makefile interpretation; for example,

  ifeq ($(CC),gcc)
          $(CC) -o foo $(objects) $(libs_for_gcc)
  else
          $(CC) -o foo $(objects) $(normal_libs)
  endif

• Conditional expansion:

  $(if condition, then-part [,else-part])
  $(or condition1[,condition2[,condition3...]])
  $(and condition1[,condition2[,condition3...]])
  
  

• Order-only prerequisites:

  targets : normal-prerequisites | order-only-prerequisites
  

  Note: clearmake does not recognize the distinction between normal and order-only prerequisites when they are specified as two different paths that have the same leaf name; for example,

   target1 : dir1/prereq1 | dir2/prereq1

• Creating parameterized functions:

  $(call variable,parameter,parameter,...)
  

  Note: With clearmake, $(call) does not support the recursive definition of a macro, as in this example, where Macro2 is using itself for its definition:

  Var1 = Val1
  Macro1 = $(1) $(2)
  Macro2= $(call  macro1, $(Var1),$(Macro2))  macro "Macro2"
  
  

• Simply expanded variables in which the RHS is expanded once when the assignment is first scanned. For example:

  y := $(x) bar

• The += syntax to append to the value of a variable.
• The ?= macro operator.
• The use of $$ in target names as an equivalent to a literal $.
• Special characters ()<>;!=&|$#:"{}\ (UNIX and Linux) or ()<>;!=&|$#:" (Windows) within macro names
• Escaping special characters in target names by preceding them with a \. Note that the escaping must be consistent within the makefile. For example,

  test: test#footest\#foo:
  echo $@test: test#footest\#foo:
  echo $@

  generates a Don't know how to make error.

• Stripping leading sequences of ./ (UNIX and Linux) or .\ (Windows) from file names, so that (for example) .\file and file are considered the same target
• Variable references using pattern substitution:

  ${VAR:PATTERN_1=PATTERN_2}

• Text-manipulation functions:

  $(subst FROM,TO,TEXT)
  $(patsubst PATTERN,REPLACEMENT,TEXT)
  $(strip STRING)
  $(findstring FIND,IN)
  $(filter PATTERN...,TEXT)
  $(filter-out PATTERN...,TEXT)
  $(sort LIST)
  $(dir NAMES...)
  $(notdir NAMES...)
  $(suffix NAMES...)
  $(basename NAMES...)
  $(addsuffix SUFFIX,NAMES...)
  $(addprefix PREFIX,NAMES...)
  $(join LIST1,LIST2)
  $(word N,TEXT)
  $(words TEXT)
  $(wordlist START, END, TEXT)
  $(firstword NAMES...)
  $(wildcard PATTERN)
  $(foreach VAR,LIST,TEXT)
  $(origin VARIABLE)
  $(shell COMMAND)
  $(value variable)
  $(warning text)
  $(error text)
  $(eval argument)
  

  Note: If $(eval argument) appears on the right-hand side of a macro that is evaluated at run-time, the results are not guaranteed. This is due to the fact that clearmake distinguishes between the parsing phase and the run-time phase. Consequently, the argument cannot be reliably parsed at run-time.
• The VPATH variable for specifying a search path for every dependency.
  Note: clearmake searches only in the current view. For more information, see the makefile_ccase reference page.
• The MAKECMDGOALS variable for specifying the targets given on the command line.
• The vpath statement for specifying a search path for a specified class of names.
• The export statement.
• The unexport directive.
• The .PHONY target declaration.
• All of GNU make's built-in implicit rules.
• Pattern rules. For example:

  %.o : %.c
      COMMANDS
      ...

• Static pattern rules:

  TARGETS ...: TARGET-PATTERN: DEP-PATTERNS ...
      COMMANDS
      ...

• The automatic variables:

  $@  $*  $<  $%  $?  $^  $+ 

  Also, their file name and directory-name variants. For example:

  $(@F)  $(@D)  ...

• Multiline variable definition:

  define VAR
      TEXT
      ...
  endef

• Target-specific variable values:

  target ... : variable-assignment

  or

  target ... : override variable-assignment

• .VARIABLES

  Expands to a list of the names of all global variables defined so far. This includes variables which have empty values, as well as built-in variables, but does not include any variables which are only defined in a target-specific context. Note that any value you assign to this variable will be ignored; it will always return its special value.

• .LIBPATTERNS

  Defines the naming of the libraries that to be searched for, and their order.

• MAKEOVERRIDES

  Refer to GNU make documentation for information about MAKEOVERRIDES.

Unsupported GNU make features

The following features are not supported:

• Wildcards in a dependency specification when any of the dependency names include embedded space characters.
• Automatic remaking of any makefiles that are declared as targets (you must explicitly rebuild them).
• The declarations .DELETE_ON_ERROR, .INTERMEDIATE, .SECONDARY.
• Automatic makefile regeneration and restart if the makefile and included makefile fragments are targets in the makefile itself.
• Automatic deletion of intermediate results of a chain of implicit-rules.
• Special search method for library dependencies written in the form -lNAME. For each directory on the VPATH/vpath list, GNU make searches in DIR/lib .
• When MAKEFILES is defined, GNU make considers its value as a list of names of additional makefiles to be read before the others, as though they were implicitly included.