Re: [PATCH v2 01/11] configure: remove all dependencies on a (re)configure

[Philippe Mathieu-Daudé]

On 7/13/20 10:04 PM, Alex Bennée wrote:
> The previous code was brittle and missed cases such as the mipn32
> variants which for some reason has the 64 bit syscalls. This leads to
> a number of binary targets having deps lines like:
> 
>   all.clang-sanitizer/mipsn32el-linux-user/linux-user/signal.d
>   140:  /home/alex/lsrc/qemu.git/linux-user/mips64/syscall_nr.h \
>   455:/home/alex/lsrc/qemu.git/linux-user/mips64/syscall_nr.h:
> 
>   all.clang-sanitizer/mipsn32el-linux-user/linux-user/syscall.d
>   146:  /home/alex/lsrc/qemu.git/linux-user/mips64/syscall_nr.h \
>   485:/home/alex/lsrc/qemu.git/linux-user/mips64/syscall_nr.h:
> 
> which in turn would trigger the re-generation of syscall_nr.h in the
> source tree (thanks to generic %/syscall_nr.h rules). The previous
> code attempts to clean it out but misses edge cases but fails.
> 
> After spending a day trying to understand how this was happening I'm
> unconvinced that there are not other such breakages possible with this
> "caching". As we add more auto-generated code to the build it is likely
> to trip up again. Apply a hammer to the problem.
> 
> Fixes: 91e5998f18 (which fixes 5f29856b852d and 4d6a835dea47)
> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>

> ---
>  configure | 15 ++++++---------
>  1 file changed, 6 insertions(+), 9 deletions(-)
> 
> diff --git a/configure b/configure
> index bc3b9ad931..e1de2f5b24 100755
> --- a/configure
> +++ b/configure
> @@ -1955,23 +1955,20 @@ EOF
>  exit 0
>  fi
>  
> -# Remove old dependency files to make sure that they get properly regenerated
> -rm -f */config-devices.mak.d
> -
>  # Remove syscall_nr.h to be sure they will be regenerated in the build
>  # directory, not in the source directory
>  for arch in alpha hppa m68k xtensa sh4 microblaze arm ppc s390x sparc 
> sparc64 \
>      i386 x86_64 mips mips64 ; do
>      # remove the file if it has been generated in the source directory
>      rm -f "${source_path}/linux-user/${arch}/syscall_nr.h"
> -    # remove the dependency files
> -    for target in ${arch}*-linux-user ; do
> -        test -d "${target}" && find "${target}" -type f -name "*.d" \
> -             -exec grep -q "${source_path}/linux-user/${arch}/syscall_nr.h" 
> {} \; \
> -             -print | while read file ; do rm "${file}" "${file%.d}.o" ; done
> -    done
>  done
>  
> +# Clean out all old dependency files. As more files are generated we
> +# run the risk of old dependencies triggering generation in the wrong
> +# places. Previous brittle attempts to be surgical tend to miss edge
> +# cases leading to wasted time and much confusion.
> +find -type f -name "*.d" -exec rm -f {} \;
> +
>  if test -z "$python"
>  then
>      error_exit "Python not found. Use --python=/path/to/python"
>