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+From 29e9322e6a8238205780107e731a51b48845f9c7 Mon Sep 17 00:00:00 2001
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+From: Julien Olivain <ju.o@free.fr>
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+Date: Mon, 10 Feb 2025 22:59:04 +0100
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+Subject: [PATCH] Makefile.am: fix parallel build
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+
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+When building fakeroot on host with large number of CPUs, compilation
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+can randomly fail. Failures were observed on hosts with 24 CPUs.
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+
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+Build logs show errors such as:
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+
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+ make -j$(nproc)
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+ ...
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+ awk -f ./wrapawk < ./wrapfunc.inp
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+ awk -f ./wrapawk < ./wrapfunc.inp
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+ ...
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+ In file included from libfakeroot.c:265:
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+ wraptmpf.h:607: error: unterminated #ifdef
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+ 607 | #ifdef __APPLE__
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+ |
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+ wraptmpf.h:601: error: unterminated #ifdef
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+ 601 | #ifdef HAVE_FTS_CHILDREN
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+ |
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+ wraptmpf.h:2: error: unterminated #ifndef
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+ 2 | #ifndef WRAPTMPF_H
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+ |
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+ ...
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+
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+The issue was observed in the builders of Buildroot Linux [1], which
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+is using fakeroot. Examples of build failures are [2], [3], [4].
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+
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+It is important to note that in all failing cases, there is
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+more that one parallel invocation of the "wrapawk" script [5].
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+
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+This script is meant to generate many output files (wrapped.h,
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+wrapdef.h, wrapstruct.h, wraptmpf.h) from a single invocation.
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+
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+The Makefile.am file is using multiple targets in an attempt to
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+reflect that generation of multiple outputs at once. See [6].
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+
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+This use of multiple targets in this rule is incorrect here. See
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+the Make manual [7]. This construct, used in Makefile.am, incorrectly
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+assumes all those targets are independant (so they can be executed in
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+parallel). They are not. In the current failing case, parallel
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+invocations will generates all their respective output files,
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+overwriting each other. This could lead to incomplete generated
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+files, resulting to the observed compilation failures.
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+
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+Note that GNU Make 4.3 introduced "Grouped Targets" for that purpose.
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+See "Rules with Grouped Targets" section in [7]. But this would add a
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+requirement on Make >= 4.3.
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+
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+For that reason, this commit fixes the issue by using a simpler
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+construct, working with all Make versions: the first output file
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+"wrapped.h" is kept as a target, and it is devlared as a
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+dependency of the three other generated files. This change makes sure
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+that only one invocation of "wrapawk" will happen at a time,
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+disregarding the number of parallel jobs requiring those generated
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+files. This has the effect of completely solving the parallel build
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+for all GNU Make versions.
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+
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+[1] https://buildroot.org/
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+[2] https://gitlab.com/buildroot.org/buildroot/-/jobs/9085451831
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+[3] https://gitlab.com/buildroot.org/buildroot/-/jobs/9085451244
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+[4] https://gitlab.com/buildroot.org/buildroot/-/jobs/9085451198
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+[5] https://salsa.debian.org/clint/fakeroot/-/blob/master/wrapawk
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+[6] https://salsa.debian.org/clint/fakeroot/-/blob/upstream/1.37/Makefile.am#L54
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+[7] https://www.gnu.org/software/make/manual/html_node/Multiple-Targets.html
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+
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+Upstream: Proposed: https://salsa.debian.org/clint/fakeroot/-/merge_requests/33
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+Signed-off-by: Julien Olivain <ju.o@free.fr>
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+---
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+ Makefile.am | 5 +++--
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+ 1 file changed, 3 insertions(+), 2 deletions(-)
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+
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+diff --git a/Makefile.am b/Makefile.am
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+index 46f01eb..ff71a8d 100644
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+--- a/Makefile.am
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++++ b/Makefile.am
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+@@ -48,12 +48,13 @@ EXTRA_DIST=wrapawk wrapawk_macosx wrapfunc.inp \
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+ CLEAN_FILES=fakerootconfig.h
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+
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+ if MACOSX
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+-wrapped.h wrapdef.h wrapstruct.h wraptmpf.h:wrapawk_macosx wrapfunc.inp
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++wrapped.h: wrapawk_macosx wrapfunc.inp
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+ awk -f $(srcdir)/wrapawk_macosx < $(srcdir)/wrapfunc.inp
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+ else !MACOSX
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+-wrapped.h wrapdef.h wrapstruct.h wraptmpf.h:wrapawk wrapfunc.inp
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++wrapped.h: wrapawk wrapfunc.inp
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+ awk -f $(srcdir)/wrapawk < $(srcdir)/wrapfunc.inp
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+ endif !MACOSX
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++wrapdef.h wrapstruct.h wraptmpf.h: wrapped.h
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+
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+ libfakeroot.lo:libfakeroot.c wrapdef.h wrapstruct.h wraptmpf.h
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+
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+--
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+2.48.1
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+
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Julien Olivain