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* [PATCH] powerpc: Avoid clang warnings around setjmp and longjmp
@ 2019-08-12  2:32 Nathan Chancellor
  2019-08-12  5:37 ` Christophe Leroy
                   ` (3 more replies)
  0 siblings, 4 replies; 20+ messages in thread
From: Nathan Chancellor @ 2019-08-12  2:32 UTC (permalink / raw)
  To: Benjamin Herrenschmidt, Paul Mackerras, Michael Ellerman,
	Nick Desaulniers
  Cc: clang-built-linux, Nathan Chancellor, linuxppc-dev, linux-kernel, stable

Commit aea447141c7e ("powerpc: Disable -Wbuiltin-requires-header when
setjmp is used") disabled -Wbuiltin-requires-header because of a warning
about the setjmp and longjmp declarations.

r367387 in clang added another diagnostic around this, complaining that
there is no jmp_buf declaration.

In file included from ../arch/powerpc/xmon/xmon.c:47:
../arch/powerpc/include/asm/setjmp.h:10:13: error: declaration of
built-in function 'setjmp' requires the declaration of the 'jmp_buf'
type, commonly provided in the header <setjmp.h>.
[-Werror,-Wincomplete-setjmp-declaration]
extern long setjmp(long *);
            ^
../arch/powerpc/include/asm/setjmp.h:11:13: error: declaration of
built-in function 'longjmp' requires the declaration of the 'jmp_buf'
type, commonly provided in the header <setjmp.h>.
[-Werror,-Wincomplete-setjmp-declaration]
extern void longjmp(long *, long);
            ^
2 errors generated.

Take the same approach as the above commit by disabling the warning for
the same reason, we provide our own longjmp/setjmp function.

Cc: stable@vger.kernel.org # 4.19+
Link: https://github.com/ClangBuiltLinux/linux/issues/625
Link: https://github.com/llvm/llvm-project/commit/3be25e79477db2d31ac46493d97eca8c20592b07
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
---

It may be worth using -fno-builtin-setjmp and -fno-builtin-longjmp
instead as it makes it clear to clang that we are not using the builtin
longjmp and setjmp functions, which I think is why these warnings are
appearing (at least according to the commit that introduced this waring).

Sample patch:
https://github.com/ClangBuiltLinux/linux/issues/625#issuecomment-519251372

However, this is the most conservative approach, as I have already had
someone notice this error when building LLVM with PGO on tip of tree
LLVM.

 arch/powerpc/kernel/Makefile | 5 +++--
 arch/powerpc/xmon/Makefile   | 5 +++--
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index ea0c69236789..44e340ed4722 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -5,8 +5,9 @@
 
 CFLAGS_ptrace.o		+= -DUTS_MACHINE='"$(UTS_MACHINE)"'
 
-# Disable clang warning for using setjmp without setjmp.h header
-CFLAGS_crash.o		+= $(call cc-disable-warning, builtin-requires-header)
+# Avoid clang warnings about longjmp and setjmp built-ins (inclusion of setjmp.h and declaration of jmp_buf type)
+CFLAGS_crash.o		+= $(call cc-disable-warning, builtin-requires-header) \
+			   $(call cc-disable-warning, incomplete-setjmp-declaration)
 
 ifdef CONFIG_PPC64
 CFLAGS_prom_init.o	+= $(NO_MINIMAL_TOC)
diff --git a/arch/powerpc/xmon/Makefile b/arch/powerpc/xmon/Makefile
index f142570ad860..53f341391210 100644
--- a/arch/powerpc/xmon/Makefile
+++ b/arch/powerpc/xmon/Makefile
@@ -1,8 +1,9 @@
 # SPDX-License-Identifier: GPL-2.0
 # Makefile for xmon
 
-# Disable clang warning for using setjmp without setjmp.h header
-subdir-ccflags-y := $(call cc-disable-warning, builtin-requires-header)
+# Avoid clang warnings about longjmp and setjmp built-ins (inclusion of setjmp.h and declaration of jmp_buf type)
+subdir-ccflags-y := $(call cc-disable-warning, builtin-requires-header) \
+		    $(call cc-disable-warning, incomplete-setjmp-declaration)
 
 GCOV_PROFILE := n
 KCOV_INSTRUMENT := n
-- 
2.23.0.rc2


^ permalink raw reply related	[flat|nested] 20+ messages in thread

end of thread, other threads:[~2019-09-10 18:39 UTC | newest]

Thread overview: 20+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-08-12  2:32 [PATCH] powerpc: Avoid clang warnings around setjmp and longjmp Nathan Chancellor
2019-08-12  5:37 ` Christophe Leroy
2019-08-12 16:55   ` Nathan Chancellor
2019-08-12 17:35 ` Nick Desaulniers
2019-08-27  0:12 ` Nathan Chancellor
2019-08-28 13:43 ` Michael Ellerman
2019-08-28 17:53   ` Nathan Chancellor
2019-08-28 18:01     ` Nick Desaulniers
2019-08-28 18:45       ` Nathan Chancellor
2019-08-28 22:16         ` Nick Desaulniers
2019-08-29  8:32           ` Segher Boessenkool
2019-08-29  9:59         ` David Laight
2019-09-03  5:55           ` Nathan Chancellor
2019-09-03 19:31             ` Segher Boessenkool
2019-09-04  0:24               ` Nathan Chancellor
2019-09-04  8:16                 ` David Laight
2019-09-04 13:01                   ` Segher Boessenkool
2019-09-04 23:15                     ` Nathan Chancellor
2019-09-10 18:30                       ` Michael Ellerman
2019-09-10 18:37                         ` Nathan Chancellor

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