From 811c8d628045c3d248144fc560a4bf80209ca16e Mon Sep 17 00:00:00 2001
From: Romain Naour <romain.naour@gmail.com>
Date: Thu, 21 May 2020 15:58:02 +0200
Subject: [PATCH] gcc/Makefile.in: move SELFTEST_DEPS before including language
 makefile fragments

As reported by several Buildroot users [1][2][3], the gcc build
may fail while running selftests makefile target.

The problem only occurs when ccache is used with gcc 9 and 10,
probably due to a race condition.

While debuging with "make -p" we can notice that s-selftest-c target
contain only "cc1" as dependency instead of cc1 and SELFTEST_DEPS [4].

  s-selftest-c: cc1

While the build is failing, the s-selftest-c dependencies recipe is
still running and reported as a bug by make.

  "Dependencies recipe running (THIS IS A BUG)."

A change [5] in gcc 9 seems to introduce the problem since we can't
reproduce this problem with gcc 8.

As suggested by Yann E. MORIN [6], move SELFTEST_DEPS before
including language makefile fragments.

With the fix applied, the s-seltest-c dependency contains
SELFTEST_DEPS value.

  s-selftest-c: cc1 xgcc specs stmp-int-hdrs ../../gcc/testsuite/selftests

[1] http://lists.busybox.net/pipermail/buildroot/2020-May/282171.html
[2] http://lists.busybox.net/pipermail/buildroot/2020-May/282766.html
[3] https://github.com/cirosantilli/linux-kernel-module-cheat/issues/108
[4] https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=gcc/c/Make-lang.in;h=bfae6fd2549c4f728816cd355fa9739dcc08fcde;hb=033eb5671769a4c681a44aad08a454e667e08502#l120
[5] https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=033eb5671769a4c681a44aad08a454e667e08502
[6] http://lists.busybox.net/pipermail/buildroot/2020-May/283213.html

Upstream status: https://gcc.gnu.org/pipermail/gcc-patches/2020-May/546248.html

Signed-off-by: Romain Naour <romain.naour@gmail.com>
Cc: Ben Dakin-Norris <ben.dakin-norris@navtechradar.com>
Cc: Maxim Kochetkov <fido_max@inbox.ru>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Cc: Yann E. MORIN <yann.morin.1998@free.fr>
Cc: Cc: David Malcolm <dmalcolm@gcc.gnu.org>
---
This patch should be backported to gcc 10 and gcc 9.
---
 gcc/Makefile.in | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/gcc/Makefile.in b/gcc/Makefile.in
index abae872cd63..e2ef3c46afc 100644
--- a/gcc/Makefile.in
+++ b/gcc/Makefile.in
@@ -1686,6 +1686,10 @@ $(FULL_DRIVER_NAME): ./xgcc
 	rm -f $@
 	$(LN_S) $< $@
 
+# SELFTEST_DEPS need to be set before including language makefile fragments.
+# Otherwise $(SELFTEST_DEPS) is empty when used from various <LANG>/Make-lang.in.
+SELFTEST_DEPS = $(GCC_PASSES) stmp-int-hdrs $(srcdir)/testsuite/selftests
+
 #
 # Language makefile fragments.
 
@@ -1950,8 +1954,6 @@ DEVNULL=$(if $(findstring mingw,$(build)),nul,/dev/null)
 SELFTEST_FLAGS = -nostdinc $(DEVNULL) -S -o $(DEVNULL) \
 	-fself-test=$(srcdir)/testsuite/selftests
 
-SELFTEST_DEPS = $(GCC_PASSES) stmp-int-hdrs $(srcdir)/testsuite/selftests
-
 # Run the selftests during the build once we have a driver and the frontend,
 # so that self-test failures are caught as early as possible.
 # Use "s-selftest-FE" to ensure that we only run the selftests if the
-- 
2.25.4