+From Darren Hart <>
+Subject [PATCH] perf: fix gcc4.6 build failure with unused-but-set warning
+Date Thu, 2 Jun 2011 13:47:48 -0700
+I ran into the following build failure with gcc 4.6:
+
+ bench/sched-pipe.c: In function 'bench_sched_pipe':
+ bench/sched-pipe.c:58:6: error: variable 'ret' set but not used
+ [-Werror=unused-but-set-variable]
+ cc1: all warnings being treated as errors
+
+As the main kernel Makefile has added -Wno-unused-but-set-variable
+and sched-pipe.c claims:
+
+ /*
+ * why does "ret" exist?
+ * discarding returned value of read(), write()
+ * causes error in building environment for perf
+ */
+This patch creates a new perf/Makefile variable, LESS_WARNINGS and
+adds -Wno-unused-but-set-variable. The new variable helps distinguish
+between the added warnings in EXTRA_WARNINGS versus those we want to
+remove, including the existing -Wno-system-headers which I moved to
+LESS_WARNINGS.
+
+Signed-off-by: Darren Hart <dvhart@linux.intel.com>
+Cc: Ingo Molnar <mingo@elte.hu>
+Cc: Bruce Ashfield <bruce.ashfield@windriver.com>
+---
+ tools/perf/Makefile | 10 ++++++++--
+ 1 files changed, 8 insertions(+), 2 deletions(-)
+diff --git a/tools/perf/Makefile b/tools/perf/Makefile
+index 032ba63..fdb35dc 100644
+--- a/tools/perf/Makefile
++++ b/tools/perf/Makefile
+@@ -74,7 +74,6 @@ EXTRA_WARNINGS := $(EXTRA_WARNINGS) -Wredundant-decls
+ EXTRA_WARNINGS := $(EXTRA_WARNINGS) -Wstrict-aliasing=3
+ EXTRA_WARNINGS := $(EXTRA_WARNINGS) -Wswitch-default
+ EXTRA_WARNINGS := $(EXTRA_WARNINGS) -Wswitch-enum
+-EXTRA_WARNINGS := $(EXTRA_WARNINGS) -Wno-system-headers
+ EXTRA_WARNINGS := $(EXTRA_WARNINGS) -Wundef
+ EXTRA_WARNINGS := $(EXTRA_WARNINGS) -Wwrite-strings
+ EXTRA_WARNINGS := $(EXTRA_WARNINGS) -Wbad-function-cast
+@@ -85,6 +84,13 @@ EXTRA_WARNINGS := $(EXTRA_WARNINGS) -Wold-style-definition
+ EXTRA_WARNINGS := $(EXTRA_WARNINGS) -Wstrict-prototypes
+ EXTRA_WARNINGS := $(EXTRA_WARNINGS) -Wdeclaration-after-statement
+
++#
++# Disable warnings that cause build problems or needlessly polute output:
++#
++
++LESS_WARNINGS := -Wno-system-headers
++LESS_WARNINGS := $(LESS_WARNINGS) -Wno-unused-but-set-variable
++
+ ifeq ("$(origin DEBUG)", "command line")
+ PERF_DEBUG = $(DEBUG)
+ endif
+@@ -92,7 +98,7 @@ ifndef PERF_DEBUG
+ CFLAGS_OPTIMIZE = -O6
+ endif
+
+-CFLAGS = -fno-omit-frame-pointer -ggdb3 -Wall -Wextra -std=gnu99 -Werror $(CFLAGS_OPTIMIZE) -D_FORTIFY_SOURCE=2 $(EXTRA_WARNINGS) $(EXTRA_CFLAGS)
++CFLAGS = -fno-omit-frame-pointer -ggdb3 -Wall -Wextra -std=gnu99 -Werror $(CFLAGS_OPTIMIZE) -D_FORTIFY_SOURCE=2 $(EXTRA_WARNINGS) $(LESS_WARNINGS) $(EXTRA_CFLAGS)
+ EXTLIBS = -lpthread -lrt -lelf -lm
+ ALL_CFLAGS = $(CFLAGS) -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64
+ ALL_LDFLAGS = $(LDFLAGS)