Re: [PATCH kernel v2] powerpc/makefile: Do not redefine $(CPP) for preprocessor
From: Segher Boessenkool <hidden>
Date: 2021-05-11 11:27:02
Also in:
linux-kbuild, lkml
Hi! On Tue, May 11, 2021 at 02:48:12PM +1000, Alexey Kardashevskiy wrote:
quoted hunk ↗ jump to hunk
--- a/arch/powerpc/kernel/vdso32/Makefile +++ b/arch/powerpc/kernel/vdso32/Makefile@@ -44,7 +44,7 @@ asflags-y := -D__VDSO32__ -s obj-y += vdso32_wrapper.o targets += vdso32.lds -CPPFLAGS_vdso32.lds += -P -C -Upowerpc +CPPFLAGS_vdso32.lds += -C # link rule for the .so file, .lds has to be first $(obj)/vdso32.so.dbg: $(src)/vdso32.lds $(obj-vdso32) $(obj)/vgettimeofday.o FORCE
quoted hunk ↗ jump to hunk
--- a/arch/powerpc/kernel/vdso64/Makefile +++ b/arch/powerpc/kernel/vdso64/Makefile@@ -30,7 +30,7 @@ ccflags-y := -shared -fno-common -fno-builtin -nostdlib \ asflags-y := -D__VDSO64__ -s targets += vdso64.lds -CPPFLAGS_vdso64.lds += -P -C -U$(ARCH) +CPPFLAGS_vdso64.lds += -C # link rule for the .so file, .lds has to be first $(obj)/vdso64.so.dbg: $(src)/vdso64.lds $(obj-vdso64) $(obj)/vgettimeofday.o FORCE
Why are you removing -P and -Upowerpc here? "powerpc" is a predefined macro on powerpc-linux (no underscores or anything, just the bareword). This is historical, like "unix" and "linux". If you use the C preprocessor for things that are not C code (like the kernel does here) you need to undefine these macros, if anything in the files you run through the preprocessor contains those words, or funny / strange / bad things will happen. Presumably at some time in the past it did contain "powerpc" somewhere. -P is to inhibit line number output. Whatever consumes the preprocessor output will have to handle line directives if you remove this flag. Did you check if this will work for everything that uses $(CPP)? In any case, please mention the reasoning (and the fact that you are removing these flags!) in the commit message. Thanks! Segher