perf Makefile: default WERROR to off.

From 4a72032828a6784d93f4becf723303a17d723544 Mon Sep 17 00:00:00 2001
From: John Spencer <[email protected]>
Date: Mon, 25 Aug 2014 21:25:43 +0200
Subject: [PATCH 2/2] perf Makefile: default WERROR to off.

Having WERROR on by default breaks build everywhere the author hasn't tested so far; including musl libc which warns about wrong includes.

The unsuspecting user will think there's something broken and only if he's coureageuous enough to grep the Makefile infrastructure find out that he may be able to get the build working with WERROR=0.

OTOH with WERROR defaulting to off, anything will work for the user and the maintainer can knowingly use WERROR=1 to do his test builds.

---
 tools/perf/config/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index 1f67aa0..b1d639a 100644
@@ -102,7 +102,7 @@ ifeq ($(call get-executable,$(BISON)),)
 endif
 
 # Treat warnings as errors unless directed not to
-ifneq ($(WERROR),0)
+ifeq ($(WERROR),1)
   CFLAGS += -Werror
 endif
 

1.8.4

I think it's intentionally turned on to fix any warnings in the first place. But yes, it might miss some non-popular systems tho..

How many errors/warnings do you see on your system (musl libc?). Any chance to post fixes instead?

Thanks,
Namhyung

yes, and it's sufficient if someone tries to build it with a newer/different compiler/libc version/whatever to make it fail. having -Werror on by default is just silly and annoying because 90% of warnings (at least with -Wall) are utterly unimportant (like unused variables etc). there's probably a good reason the kernel itself is not built with -Werror.

(in my head i call people hardcoding -Werror "Werror-nazis"...)

but i agree that *some* warnings should be fatal, for example implicit function declarations, or pointer-to-int casts, because those can actually break code.

there are tons of warnings, mostly from mixing kernel headers with userspace headers (and libc_compat.h is only patched for GLIBC - my musl-related libc_compat.h patches have been ignored so far, but they're archived at https://github.com/sabotage-linux/kernel-headers ).

In file included from perf.c:12:0:
util/cache.h:74:15: warning: redundant redeclaration of 'strlcpy' [-Wredundant-decls] In file included from util/util.h:53:0,

                 from builtin.h:4,
                 from perf.c:9:
/usr/include/string.h:84:8: note: previous declaration of 'strlcpy' was here
In file included from util/util.h:67:0,
                 from builtin.h:4,
                 from perf.c:9:

/usr/include/sys/poll.h:1:2: warning: #warning redirecting incorrect #include <sys/poll.h> to <poll.h> [-Wcpp] In file included from /src/build/kernel/linux-3.14.14.org/arch/x86/include/uapi/asm/ioctl.h:1:0,
from
/src/build/kernel/linux-3.14.14.org/include/uapi/linux/ioctl.h:4,
from
/src/build/kernel/linux-3.14.14.org/include/uapi/linux/perf_event.h:18,

                 from util/../perf.h:156,
                 from util/cache.h:7,
                 from perf.c:12:
/src/build/kernel/linux-3.14.14.org/include/uapi/asm-generic/ioctl.h:65:0: warning: "_IOC" redefined [enabled by default]
In file included from /usr/include/sys/ioctl.h:7:0,
                 from util/util.h:69,
                 from builtin.h:4,
                 from perf.c:9:

/usr/include/bits/ioctl.h:1:0: note: this is the location of the previous definition In file included from /src/build/kernel/linux-3.14.14.org/arch/x86/include/uapi/asm/ioctl.h:1:0,
from
/src/build/kernel/linux-3.14.14.org/include/uapi/linux/ioctl.h:4,
from
/src/build/kernel/linux-3.14.14.org/include/uapi/linux/perf_event.h:18,

                 from util/../perf.h:156,
                 from util/cache.h:7,
                 from perf.c:12:

/src/build/kernel/linux-3.14.14.org/include/uapi/asm-generic/ioctl.h:76:0: warning: "_IO" redefined [enabled by default]

(same for _IOR, _IOW, _IOWR, _IOC)

these warnings are repeated over an over again as they come from headers.
so basically we have
- util/cache.h:74:15: warning: redundant redeclaration of 'strlcpy'
- uapi/asm-generic/ioctl.h: warning: "_IO*" redefined (userspace and kernel space defining the same thing)
- util/util.h: incorrect inclusion of sys/poll.h rather than poll.h (see man 3p poll)
tho it's possible I may have missed something else in the wall of warnings.

Thanks,
--JS