buildroot/package/fwts/0002-libfwtsiasl-fix-parallel-build-with-GNU-Make-4.4.patch

From 65a89b6253ef527ab4bc951eb8f9deba12f0121a Mon Sep 17 00:00:00 2001
From: Julien Olivain <ju.o@free.fr>
Date: Mon, 20 May 2024 11:14:02 +0200
Subject: [PATCH] libfwtsiasl: fix parallel build with GNU Make >= 4.4

When a build host has a large number of cores (like 20+) and GNU Make
version is >= 4.4, fwts randomly fail to build in parallel, with a
"make -j$(nproc)" command, with error:

    mv: cannot stat 'dtcompilerparser.tab.c': No such file or directory
    mv: cannot stat 'prparser.tab.c': No such file or directory

This issue has been reported here:
https://github.com/fwts/fwts/issues/7

The Makefile.am of libfwtsiasl is using the GNU Make ".NOTPARALLEL"
special target with prerequisites to handle commands generating
multiple outputs (like lex/yacc invocations). See:
https://github.com/fwts/fwts/blob/V24.03.00/src/libfwtsiasl/Makefile.am#L61

First, the .NOTPARALLEL special target _with_ prerequisites is a
feature added in GNU Make 4.4. See:
https://git.savannah.gnu.org/cgit/make.git/commit/?id=f6ea899d83bf00fe9201fde0ca9cf7af8e443677
https://lists.gnu.org/archive/html/help-make/2022-10/msg00020.html

GNU Make version < 4.4 will interpret it as if it was written without
prerequisite (as a standalone ".NOTPARALLEL:"). The effect is that the
parallel compilation is disabled for the whole libfwtsiasl. The
standalone .NOTPARALLEL special target was introduced in GNU Make 3.79
in 2000. This is why parallel builds are working with Make older than
version 4.4.

Secondly, the reason why the build is failing on GNU Make >= 4.4 is
because the usage of .NOTPARALLEL in incorrect.

Quoting the Make manual:
https://www.gnu.org/software/make/manual/html_node/Parallel-Disable.html
"""
If the .NOTPARALLEL special target has prerequisites, then each of those
prerequisites will be considered a target and all prerequisites of these
targets will be run serially.
"""

Note the serialization will happen on the prerequisites of the targets
set as prerequisites of .NOTPARALLEL.

The targets will not be correctly marked to disable parallel
execution.

Thirdly, the use of multiple targets in a rule is incorrect here. See
Make manual:
https://www.gnu.org/software/make/manual/html_node/Multiple-Targets.html
The construct used in Makefile.am of libfwtsiasl for lex/yacc parsers
assumes they are independant targets (so they can be executed in
parallel). Finally, the "mv" command is failing, because there will be
one parallel execution per target, the first mv will suceed and the
other ones will fail. Multiple independant targets are often used in
Makefiles for lex/yacc, they are working because they are not using
"mv". Even in multiple execution, files are just overwritten.

Fixing this .NOTPARALLEL usage with prerequisites would require Make
version 4.4 or greater. This is a strong requirement, as there is
still many Linux distros with older Make version (as an example Ubuntu
22.04 LTS has Make 4.3).

The .WAIT special target could be used, but was also introduced in
Make version 4.4. See:
https://git.savannah.gnu.org/cgit/make.git/commit/?id=f6ea899d83bf00fe9201fde0ca9cf7af8e443677

GNU Make 4.3 also introduced "Grouped Targets" for that purpose. See:
https://www.gnu.org/software/make/manual/html_node/Multiple-Targets.html
But this would add a requirement on a recent Make version.

This commit fixes the issue by declaring the first generated file as a
dependency of the other extra generated files. This has the effect of
completely solving the parallel build for all GNU Make versions. Also,
this enables parallel build for libfwtsiasl (except for the parser
generation) and makes the whole build faster.

Signed-off-by: Julien Olivain <ju.o@free.fr>
Upstream: https://github.com/fwts/fwts/commit/c0962cd74c725418523c46ca44101e0e70201f81
---
 src/libfwtsiasl/Makefile.am | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/src/libfwtsiasl/Makefile.am b/src/libfwtsiasl/Makefile.am
index cb10bc58..ac54f621 100644
--- a/src/libfwtsiasl/Makefile.am
+++ b/src/libfwtsiasl/Makefile.am
@@ -58,32 +58,32 @@ aslcompiler.y: $(ASL_PARSER)
 aslcompilerlex.c: $(ASL_LEXER)
 	${LEX} ${AM_LFLAGS} -PAslCompiler -o$@ $(top_srcdir)/src/acpica/source/compiler/aslcompiler.l
 
-.NOTPARALLEL: aslcompiler.c
-aslcompiler.c aslcompiler.y.h: aslcompiler.y
+aslcompiler.c: aslcompiler.y
 	${YACC} ${AM_YFLAGS} -d -baslcompiler -pAslCompiler $^
 	mv aslcompiler.tab.c aslcompiler.c
 	cp aslcompiler.tab.h aslcompiler.y.h
+aslcompiler.y.h: aslcompiler.c
 
-.NOTPARALLEL: dtcompilerparserlex.c
-dtcompilerparserlex.c dtcompilerparser.c dtcompilerparser.y.h: $(top_srcdir)/src/acpica/source/compiler/dtcompilerparser.l $(top_srcdir)/src/acpica/source/compiler/dtcompilerparser.y
+dtcompilerparserlex.c: $(top_srcdir)/src/acpica/source/compiler/dtcompilerparser.l $(top_srcdir)/src/acpica/source/compiler/dtcompilerparser.y
 	${LEX} ${AM_LFLAGS} -PDtCompilerParser -odtcompilerparserlex.c $<
 	${YACC} ${AM_YFLAGS} -bdtcompilerparser -pDtCompilerParser $(top_srcdir)/src/acpica/source/compiler/dtcompilerparser.y
 	mv dtcompilerparser.tab.c dtcompilerparser.c
 	cp dtcompilerparser.tab.h dtcompilerparser.y.h
+dtcompilerparser.c dtcompilerparser.y.h: dtcompilerparserlex.c
 
-.NOTPARALLEL: dtparserlex.c
-dtparserlex.c dtparser.c dtparser.y.h: $(top_srcdir)/src/acpica/source/compiler/dtparser.l $(top_srcdir)/src/acpica/source/compiler/dtparser.y
+dtparserlex.c: $(top_srcdir)/src/acpica/source/compiler/dtparser.l $(top_srcdir)/src/acpica/source/compiler/dtparser.y
 	${LEX} ${AM_LFLAGS} -PDtParser -odtparserlex.c $<
 	${YACC} ${AM_YFLAGS} -bdtparser -pDtParser $(top_srcdir)/src/acpica/source/compiler/dtparser.y
 	mv dtparser.tab.c dtparser.c
 	cp dtparser.tab.h dtparser.y.h
+dtparser.c dtparser.y.h: dtparserlex.c
 
-.NOTPARALLEL: prparserlex.c
-prparserlex.c prparser.c prparser.y.h: $(top_srcdir)/src/acpica/source/compiler/prparser.l $(top_srcdir)/src/acpica/source/compiler/prparser.y
+prparserlex.c: $(top_srcdir)/src/acpica/source/compiler/prparser.l $(top_srcdir)/src/acpica/source/compiler/prparser.y
 	${LEX} ${AM_LFLAGS} -PPrParser -oprparserlex.c $<
 	${YACC} ${AM_YFLAGS} -bprparser -pPrParser $(top_srcdir)/src/acpica/source/compiler/prparser.y
 	mv prparser.tab.c prparser.c
 	cp prparser.tab.h prparser.y.h
+prparser.c prparser.y.h: prparserlex.c
 
 pkglib_LTLIBRARIES = libfwtsiasl.la
 
-- 
2.45.1