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

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Date:   Mon, 3 Jan 2022 16:29:31 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     cgel.zte@...il.com
Cc:     Michal Marek <michal.lkml@...kovi.net>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        xu xin <xu.xin16@....com.cn>
Subject: Re: [PATCH] Fix compilation errors when using special directory

On Fri, Dec 31, 2021 at 4:56 PM <cgel.zte@...il.com> wrote:
>
> From: xu xin <xu.xin16@....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.
>
> Signed-off-by: xu xin <xu.xin16@....com.cn>


This depends on what shell you are using.


If you use a modern shell like bash,
~ is expanded into the home directory path
on the shell side.

So, Make will see the absolute path.
In contrast, dash does not expand ~.


[Test code]
$(warning CROSS_COMPILE is $(CROSS_COMPILE))
all:
        @:



[Result]
masahiro@...ver:/tmp$ bash
masahiro@...ver:/tmp$ make
CROSS_COMPILE=~/x86_64_gcc9.2.0_glibc2.31.0/bin/x86_64-pc-linux-gnu-
all
Makefile:1: CROSS_COMPILE is
/home/masahiro/x86_64_gcc9.2.0_glibc2.31.0/bin/x86_64-pc-linux-gnu-
masahiro@...ver:/tmp$ dash
$ make CROSS_COMPILE=~/x86_64_gcc9.2.0_glibc2.31.0/bin/x86_64-pc-linux-gnu- all
Makefile:1: CROSS_COMPILE is
~/x86_64_gcc9.2.0_glibc2.31.0/bin/x86_64-pc-linux-gnu-





Moreover, your patch does not work at all because
the $(realpath ) built-in function does not expand ~.

~ is a shell's special character (and only some shells recognize it).
GNU Make is completely agnostic about such a character.



If you are using such a shell that does not understand ~,
as Nathan suggested, you can use $HOME.



> ---
>  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
>


--
Best Regards
Masahiro Yamada