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Diffstat (limited to 'src')
| -rw-r--r-- | src/development/make.md | 96 |
1 files changed, 95 insertions, 1 deletions
diff --git a/src/development/make.md b/src/development/make.md index fdef47e..38da4fa 100644 --- a/src/development/make.md +++ b/src/development/make.md @@ -13,7 +13,7 @@ target .. : prerequisite .. > Use `make -p` to print all rules and variables (implicitly + explicitly defined). -## Pattern rules & Automatic variables +## Pattern rules & variables ### Pattern rules A pattern rule contains the `%` char (exactly one of them) and look like this example: ```make @@ -72,6 +72,22 @@ Running above `Makefile` gives: Variables related to filesystem paths: - `$(CURDIR)`: Path of current working dir after using `make -C path` +### Multi-line variables +```make +define my_var +@echo foo +@echo bar +endef + +all: + $(my_var) +``` +Running above `Makefile` gives: +```text +foo +bar +``` + ## Arguments Arguments specified on the command line *override* ordinary variable @@ -130,6 +146,7 @@ out := $(filter-out %.b %.c, $(in)) Resolve each file name as absolute path (don't resolve symlinks). ```make $(abspath fname1 fname2 ..) +``` ### `realpath` Resolve each file name as canonical path. @@ -137,6 +154,53 @@ Resolve each file name as canonical path. $(realpath fname1 fname2 ..) ``` +### `call` ([ref][make-call]) +Invoke parametrized function, which is an expression saved in a variable. +```make +swap = $(2) $(1) + +all: + @echo "call swap first second -> $(call swap,first,second)" +``` +Outputs: +```text +call swap first second -> second first +``` + +### `eval` ([ref][make-eval]) +Allows to define new makefile constructs by evaluating the result of a variable +or function. +```make +define new_rule +$(1): + @echo "$(1) -> $(2)" +endef + +default: rule1 rule2 + +$(eval $(call new_rule,rule1,foo)) +$(eval $(call new_rule,rule2,bar)) +``` +Outputs: +```text +rule1 -> foo +rule2 -> bar +``` + +### foreach ([ref][make-foreach]) +Repeat a piece of text for a list of values, given the syntax `$(foreach +var,list,text)`. +```make +myfn = x$(1)x + +default: + @echo $(foreach V,foo bar baz,$(call myfn,$(V))) +``` +Outputs: +```text +xfoox xbarx xbazx +``` + ## Examples ### Config based settings @@ -172,5 +236,35 @@ conf-y: default foo bar libs-y: libdef libfoo libbar ``` +### Using `foreach / eval / call` to generate new rules +```make +define new_rule +$(1): + @echo "$(1) -> $(2)" +endef + +arg-rule1 = foo +arg-rule2 = bar + +RULES = rule1 rule2 + +all: $(RULES) + +$(foreach R,$(RULES),$(eval $(call new_rule,$(R),$(arg-$(R))))) + +# equivalent to +# $(eval $(call new_rule,rule1,foo)) +# $(eval $(call new_rule,rule2,bar)) +``` +Outputs: +```text +rule1 -> foo +rule2 -> bar +``` +> Use `make -R -p` to print the make database including the rules. + [make-var-override]: https://www.gnu.org/software/make/manual/html_node/Overriding.html [make-patsubst]: https://www.gnu.org/software/make/manual/html_node/Text-Functions.html#index-patsubst-1 +[make-call]: https://www.gnu.org/software/make/manual/html_node/Call-Function.html +[make-eval]: https://www.gnu.org/software/make/manual/html_node/Eval-Function.html +[make-foreach]: https://www.gnu.org/software/make/manual/html_node/Foreach-Function.html |