Some older systems still compile kernels with old gcc version.
$ grep -B3 "^GNU C" linux-5.10.223-rc1/Documentation/Changes
====================== =============== ========================================
Program Minimal version Command to check the version
====================== =============== ========================================
GNU C 4.9 gcc --version
These warnings and errors show up when compiling with gcc 4.9.2
UPD include/config/kernel.release
UPD include/generated/uapi/linux/version.h
UPD include/generated/utsrelease.h
CC scripts/mod/empty.o
In file included from ././include/linux/compiler_types.h:65:0,
from <command-line>:0:
./include/linux/compiler_attributes.h:29:29: warning: "__GCC4_has_attribute___uninitialized__" is not defined [-Wundef]
# define __has_attribute(x) __GCC4_has_attribute_##x
^
./include/linux/compiler_attributes.h:278:5: note: in expansion of macro '__has_attribute'
#if __has_attribute(__uninitialized__)
^
[SNIP]
AR arch/x86/events/built-in.a
CC arch/x86/kvm/../../../virt/kvm/kvm_main.o
In file included from ././include/linux/compiler_types.h:65:0,
from <command-line>:0:
./include/linux/compiler_attributes.h:29:29: error: "__GCC4_has_attribute___uninitialized__" is not defined [-Werror=undef]
# define __has_attribute(x) __GCC4_has_attribute_##x
^
./include/linux/compiler_attributes.h:278:5: note: in expansion of macro '__has_attribute'
#if __has_attribute(__uninitialized__)
^
cc1: all warnings being treated as errors
make[2]: *** [scripts/Makefile.build:286: arch/x86/kvm/../../../virt/kvm/kvm_main.o] Error 1
make[1]: *** [scripts/Makefile.build:503: arch/x86/kvm] Error 2
make: *** [Makefile:1832: arch/x86] Error 2
Following patch fixes this. Upstream won't need this because
newer kernels are not compilable with gcc 4.9
--- ./include/linux/compiler_attributes.h.OLD
+++ ./include/linux/compiler_attributes.h
@@ -37,6 +37,7 @@
# define __GCC4_has_attribute___nonstring__ 0
# define __GCC4_has_attribute___no_sanitize_address__ (__GNUC_MINOR__ >= 8)
# define __GCC4_has_attribute___no_sanitize_undefined__ (__GNUC_MINOR__ >= 9)
+# define __GCC4_has_attribute___uninitialized__ 0
# define __GCC4_has_attribute___fallthrough__ 0
# define __GCC4_has_attribute___warning__ 1
#endif
Fixes: upstream fd7eea27a3ae "Compiler Attributes: Add __uninitialized macro"
Signed-off-by: Jari Ruusu <jariruusu@xxxxxxxxxxxxxx>
--
Jari Ruusu 4096R/8132F189 12D6 4C3A DCDA 0AA4 27BD ACDF F073 3C80 8132 F189
