linux/scripts/genksyms
Masahiro Yamada 6ba7dc6616 kbuild: make bison create C file and header in a single pattern rule
We generally expect bison to create not only a C file, but also a
header, which will be included from the lexer.

Currently, Kbuild generates them in separate rules. So, for instance,
when building Kconfig, you will notice bison is invoked twice:

  HOSTCC  scripts/kconfig/conf.o
  HOSTCC  scripts/kconfig/confdata.o
  HOSTCC  scripts/kconfig/expr.o
  LEX     scripts/kconfig/lexer.lex.c
  YACC    scripts/kconfig/parser.tab.h
  HOSTCC  scripts/kconfig/lexer.lex.o
  YACC    scripts/kconfig/parser.tab.c
  HOSTCC  scripts/kconfig/parser.tab.o
  HOSTCC  scripts/kconfig/preprocess.o
  HOSTCC  scripts/kconfig/symbol.o
  HOSTLD  scripts/kconfig/conf

Make handles such cases nicely in pattern rules [1]. Merge the two
rules so that one invokcation of bison can generate both of them.

  HOSTCC  scripts/kconfig/conf.o
  HOSTCC  scripts/kconfig/confdata.o
  HOSTCC  scripts/kconfig/expr.o
  LEX     scripts/kconfig/lexer.lex.c
  YACC    scripts/kconfig/parser.tab.[ch]
  HOSTCC  scripts/kconfig/lexer.lex.o
  HOSTCC  scripts/kconfig/parser.tab.o
  HOSTCC  scripts/kconfig/preprocess.o
  HOSTCC  scripts/kconfig/symbol.o
  HOSTLD  scripts/kconfig/conf

[1] Pattern rule

GNU Make manual says:
"Pattern rules may have more than one target. Unlike normal rules,
this does not act as many different rules with the same prerequisites
and recipe. If a pattern rule has multiple targets, make knows that
the rule's recipe is responsible for making all of the targets. The
recipe is executed only once to make all the targets. When searching
for a pattern rule to match a target, the target patterns of a rule
other than the one that matches the target in need of a rule are
incidental: make worries only about giving a recipe and prerequisites
to the file presently in question. However, when this file's recipe is
run, the other targets are marked as having been updated themselves."

https://www.gnu.org/software/make/manual/html_node/Pattern-Intro.html

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2019-08-14 01:10:42 +09:00
..
.gitignore .gitignore: move *.lex.c *.tab.[ch] patterns to the top-level .gitignore 2018-04-07 19:04:02 +09:00
genksyms.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 156 2019-05-30 11:26:35 -07:00
genksyms.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 156 2019-05-30 11:26:35 -07:00
keywords.c genksyms: Teach parser about 128-bit built-in types 2019-06-24 03:43:03 +09:00
lex.l genksyms: fix gperf removal conversion 2017-09-08 14:32:34 -07:00
Makefile kbuild: make bison create C file and header in a single pattern rule 2019-08-14 01:10:42 +09:00
parse.y genksyms: Teach parser about 128-bit built-in types 2019-06-24 03:43:03 +09:00