On 12/26/20 16:35, h...@zytor.com wrote: > Why is CLANG_FLAGS non-null when unused? It would be better to centralize > that. CLANG_FLAGS normally propagates through inclusion in the default KBUILD_CFLAGS and KBUILD_AFLAGS, set in `/Makefile':
# Makefile KBUILD_CFLAGS += $(CLANG_FLAGS) KBUILD_AFLAGS += $(CLANG_FLAGS) export CLANG_FLAGS This default can be overridden by explicit assignment, as is done in some of the arch/x86 makefiles: # arch/x86/realmode/rm/Makefile KBUILD_CFLAGS := $(REALMODE_CFLAGS) -D_SETUP -D_WAKEUP \ -I$(srctree)/arch/x86/boot KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__ KBUILD_CFLAGS += -fno-asynchronous-unwind-tables Since REALMODE_CFLAGS is being built up from a plain assignment, the Clang flags get lost. As a result Clang fails to compile the real-mode code when cross-compiling for an x86 target. arch/x86/realmode/rm/header.S:36:1: error: unknown directive .type real_mode_header STT_OBJECT ; .size real_mode_header, .-real_mode_header ^ arch/x86/realmode/rm/header.S:36:37: error: unknown directive .type real_mode_header STT_OBJECT ; .size real_mode_header, .-real_mode_header ^ arch/x86/realmode/rm/header.S:41:62: error: unknown directive .globl end_signature ; ; end_signature: ; .long 0x65a22c82 ; .type end_signature STT_OBJECT ; .size end_signature, .-end_signature ^ arch/x86/realmode/rm/header.S:41:95: error: unknown directive .globl end_signature ; ; end_signature: ; .long 0x65a22c82 ; .type end_signature STT_OBJECT ; .size end_signature, .-end_signature ^ This patch allows the Clang-specific flags to propagate through the REALMODE_CFLAGS variable set in `arch/x86/Makefile' and consumed by certain arch/x86 targets, which fixes cross-compilation of x86 kernels.
