linux-kernel - [PATCH 2/2] arch: mips: Fix non-POSIX regexp

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Date:   Thu,  8 Jul 2021 10:57:10 +0200
From:   "H. Nikolaus Schaller" <hns@...delico.com>
To:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, Jessica Yu <jeyu@...nel.org>,
        Miroslav Benes <mbenes@...e.cz>,
        Emil Velikov <emil.l.velikov@...il.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     letux-kernel@...nphoenux.org, "H. Peter Anvin" <hpa@...or.com>,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel@...a-handheld.com,
        "H. Nikolaus Schaller" <hns@...delico.com>
Subject: [PATCH 2/2] arch: mips: Fix non-POSIX regexp

When cross compiling a MIPS kernel on a BSD based HOSTCC leads
to errors like

  SYNC    include/config/auto.conf.cmd - due to: .config
egrep: empty (sub)expression
  UPD     include/config/kernel.release
  HOSTCC  scripts/dtc/dtc.o - due to target missing

It turns out that egrep uses this egrep pattern:

		(|MINOR_|PATCHLEVEL_)

This is not valid syntax or gives undefined results according
to POSIX 9.5.3 ERE Grammar

	https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html

It seems to be silently accepted by the Linux egrep implementation
while a BSD host complains.

Such patterns can be replaced by a transformation like

	"(|p1|p2)" -> "(p1|p2)?"

Fixes: 48c35b2d245f ("[MIPS] There is no __GNUC_MAJOR__")
Signed-off-by: H. Nikolaus Schaller <hns@...delico.com>
---
 arch/mips/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/mips/Makefile b/arch/mips/Makefile
index 258234c35a096..674f68d16a73f 100644
--- a/arch/mips/Makefile
+++ b/arch/mips/Makefile
@@ -321,7 +321,7 @@ KBUILD_LDFLAGS		+= -m $(ld-emul)
 
 ifdef CONFIG_MIPS
 CHECKFLAGS += $(shell $(CC) $(KBUILD_CFLAGS) -dM -E -x c /dev/null | \
-	egrep -vw '__GNUC_(|MINOR_|PATCHLEVEL_)_' | \
+	egrep -vw '__GNUC_(MINOR_|PATCHLEVEL_)?_' | \
 	sed -e "s/^\#define /-D'/" -e "s/ /'='/" -e "s/$$/'/" -e 's/\$$/&&/g')
 endif
 
-- 
2.31.1