Re: [PATCH] Fix compilation errors when using special directory

[Nathan Chancellor <nathan@kernel.org>]

On Fri, Dec 31, 2021 at 07:55:51AM +0000, cgel.zte@gmail.com wrote:
> From: xu xin <xu.xin16@zte.com.cn>
> 
> When we compile the kernel with cross compilers, if CROSS_COMPILE is
> specified by the path containing special directory like '~', some
> compilation error will occurs.
> 
> Here's an example:
> 
> $ make ARCH=x86_64
> CROSS_COMPILE=~/x86_64_gcc9.2.0_glibc2.31.0/bin/x86_64-pc-linux-gnu- all
> 
> error:./scripts/mkcompile_h: line 64:
> ~/x86_64_gcc9.2.0_glibc2.31.0/bin/x86_64-pc-linux-gnu-ld: No such file or
> directory
> 
> Since there are many other similar scripts using these variables, in
> order to solve the problem from the source, add realpath in makefile to
> turn these variables into absolute paths.

This is not going to work for the traditional approach of CROSS_COMPILE
being just a triple, rather than a full path plus a triple, because

$(realpath $(CROSS_COMPILE))

is going to evaluate to nothing in that case:

$ make -skj"$(nproc)" ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- defconfig all
warning: ld does not support --fix-cortex-a53-843419; kernel may be susceptible to erratum
ld: unrecognised emulation mode: aarch64linux
Supported emulations: elf_x86_64 elf32_x86_64 elf_i386 elf_iamcu elf_l1om elf_k1om i386pep i386pe
make[2]: *** [arch/arm64/kernel/vdso/Makefile:57: arch/arm64/kernel/vdso/vdso.so.dbg] Error 1
...

Why not just change '~' to '$HOME' in your build scripts so that it is
evaluated before the make command begins?

> Signed-off-by: xu xin <xu.xin16@zte.com.cn>
> ---
>  Makefile | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/Makefile b/Makefile
> index fe5a4d8e4ac5..cdbb747787ac 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -459,14 +459,14 @@ OBJDUMP		= llvm-objdump
>  READELF		= llvm-readelf
>  STRIP		= llvm-strip
>  else
> -CC		= $(CROSS_COMPILE)gcc
> -LD		= $(CROSS_COMPILE)ld
> -AR		= $(CROSS_COMPILE)ar
> -NM		= $(CROSS_COMPILE)nm
> -OBJCOPY		= $(CROSS_COMPILE)objcopy
> -OBJDUMP		= $(CROSS_COMPILE)objdump
> -READELF		= $(CROSS_COMPILE)readelf
> -STRIP		= $(CROSS_COMPILE)strip
> +CC		= $(realpath $(CROSS_COMPILE))gcc
> +LD		= $(realpath $(CROSS_COMPILE))ld
> +AR		= $(realpath $(CROSS_COMPILE))ar
> +NM		= $(realpath $(CROSS_COMPILE))nm
> +OBJCOPY		= $(realpath $(CROSS_COMPILE))objcopy
> +OBJDUMP		= $(realpath $(CROSS_COMPILE))objdump
> +READELF		= $(realpath $(CROSS_COMPILE))readelf
> +STRIP		= $(realpath $(CROSS_COMPILE))strip
>  endif
>  RUSTC		= rustc
>  RUSTDOC		= rustdoc
> -- 
> 2.25.1
>