From 2cd55c68c0a49a75433b15c7dbd1991fef81e662 Mon Sep 17 00:00:00 2001 From: Ian Munsie Date: Tue, 15 Sep 2015 15:48:34 +1000 Subject: [PATCH] cxl: Fix build failure due to -Wunused-variable behaviour change MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit A recent change in gcc caused this build failure: /var/lib/jenkins/workspace/gcc_kernel_build/linux/drivers/misc/cxl/cxl.h:72:27: error: ‘CXL_PSL_DLCNTL’ defined but not used [-Werror=unused-const-variable] static const cxl_p1_reg_t CXL_PSL_DLCNTL = {0x0060}; Because of this gcc commit: Commit 1bca8cbd0c68366f07277f98ce6963e10c2aa617 by mark PR28901 -Wunused-variable ignores unused const initialised variables in C 12 years ago it was decided that -Wunused-variable shouldn't warn about static const variables because some code used const static char rcsid[] strings which were never used but wanted in the code anyway. But as the bug points out this hides some real bugs. These days the usage of rcsids is not very popular anymore. So this patch changes the default to warn about unused static const variables in C with -Wunused-variable. And it adds a new option -Wno-unused-const-variable to turn this warning off. For C++ this new warning is off by default, since const variables can be used as #defines in C++. New testcases for the new defaults in C and C++ are included testing the new warning and suppressing it with an unused attribute or using -Wno-unused-const-variable. gcc/ChangeLog The cxl driver uses static consts in place of #defines in some cases for type safety, so this change causes the driver to fail to build on new copilers as these constants are not all used in every file that imports the header. Suppress the warning for this driver to return to the old behaviour of -Wunused-variable. Reported-by: Anton Blanchard Signed-off-by: Ian Munsie Signed-off-by: Michael Ellerman --- drivers/misc/cxl/Makefile | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/misc/cxl/Makefile b/drivers/misc/cxl/Makefile index 6f484dfe78f9..6982f603fadc 100644 --- a/drivers/misc/cxl/Makefile +++ b/drivers/misc/cxl/Makefile @@ -1,4 +1,4 @@ -ccflags-y := -Werror +ccflags-y := -Werror -Wno-unused-const-variable cxl-y += main.o file.o irq.o fault.o native.o cxl-y += context.o sysfs.o debugfs.o pci.o trace.o