Re: [SECOND RESEND] [PATCH] tools/python: Pass linker to Python build process

[Wei Liu <wl@xxxxxxx>]

On Sun, Oct 11, 2020 at 06:11:39PM -0700, Elliott Mitchell wrote:
> Unexpectedly the environment variable which needs to be passed is
> $LDSHARED and not $LD.  Otherwise Python may find the build `ld` instead
> of the host `ld`.
> 
> Replace $(LDFLAGS) with $(SHLIB_LDFLAGS) as Python needs shared objects
> it can load at runtime, not executables.
> 
> This uses $(CC) instead of $(LD) since Python distutils appends $CFLAGS
> to $LDFLAGS which breaks many linkers.
> 
> Signed-off-by: Elliott Mitchell <ehem+xen@xxxxxxx>
> ---
> This is now the *third* time this has been sent to the list.  Mark Pryor
> has tested and confirms Python cross-building is working.  There is one
> wart left which I'm unsure of the best approach for.
> 
> Having looked around a bit, I believe this is a Python 2/3 compatibility
> issue.  "distutils" for Python 2 likely lacked a separate $LDSHARED or
> $LD variable, whereas Python 3 does have this.  Alas this is pointless
> due to the above (unless you can cause distutils.py to do the final link
> step separately).

I think this is well-reasoned but I don't have time to figure out and
verify the details.

Marek, do you have any comment on this?

> ---
>  tools/pygrub/Makefile | 9 +++++----
>  tools/python/Makefile | 9 +++++----
>  2 files changed, 10 insertions(+), 8 deletions(-)
> 
> diff --git a/tools/pygrub/Makefile b/tools/pygrub/Makefile
> index 3063c4998f..37b2146214 100644
> --- a/tools/pygrub/Makefile
> +++ b/tools/pygrub/Makefile
> @@ -3,20 +3,21 @@ XEN_ROOT = $(CURDIR)/../..
>  include $(XEN_ROOT)/tools/Rules.mk
>  
>  PY_CFLAGS = $(CFLAGS) $(PY_NOOPT_CFLAGS)
> -PY_LDFLAGS = $(LDFLAGS) $(APPEND_LDFLAGS)
> +PY_LDFLAGS = $(SHLIB_LDFLAGS) $(APPEND_LDFLAGS)
>  INSTALL_LOG = build/installed_files.txt
>  
>  .PHONY: all
>  all: build
>  .PHONY: build
>  build:
> -     CC="$(CC)" CFLAGS="$(PY_CFLAGS)" LDFLAGS="$(PY_LDFLAGS)" $(PYTHON) 
> setup.py build
> +     CC="$(CC)" CFLAGS="$(PY_CFLAGS)" LDSHARED="$(CC)" 
> LDFLAGS="$(PY_LDFLAGS)" $(PYTHON) setup.py build
>  
>  .PHONY: install
>  install: all
>       $(INSTALL_DIR) $(DESTDIR)/$(bindir)
> -     CC="$(CC)" CFLAGS="$(PY_CFLAGS)" LDFLAGS="$(PY_LDFLAGS)" $(PYTHON) \
> -             setup.py install --record $(INSTALL_LOG) $(PYTHON_PREFIX_ARG) \
> +     CC="$(CC)" CFLAGS="$(PY_CFLAGS)" LDSHARED="$(CC)" \
> +             LDFLAGS="$(PY_LDFLAGS)" $(PYTHON) setup.py install \
> +             --record $(INSTALL_LOG) $(PYTHON_PREFIX_ARG) \
>                --root="$(DESTDIR)" --install-scripts=$(LIBEXEC_BIN) --force
>       set -e; if [ $(bindir) != $(LIBEXEC_BIN) -a \
>                    "`readlink -f $(DESTDIR)/$(bindir)`" != \
> diff --git a/tools/python/Makefile b/tools/python/Makefile
> index 8d22c03676..b675f5b4de 100644
> --- a/tools/python/Makefile
> +++ b/tools/python/Makefile
> @@ -5,19 +5,20 @@ include $(XEN_ROOT)/tools/Rules.mk
>  all: build
>  
>  PY_CFLAGS = $(CFLAGS) $(PY_NOOPT_CFLAGS)
> -PY_LDFLAGS = $(LDFLAGS) $(APPEND_LDFLAGS)
> +PY_LDFLAGS = $(SHLIB_LDFLAGS) $(APPEND_LDFLAGS)
>  INSTALL_LOG = build/installed_files.txt
>  
>  .PHONY: build
>  build:
> -     CC="$(CC)" CFLAGS="$(PY_CFLAGS)" $(PYTHON) setup.py build
> +     CC="$(CC)" CFLAGS="$(PY_CFLAGS)" LDSHARED="$(CC)" 
> LDFLAGS="$(PY_LDFLAGS)" $(PYTHON) setup.py build
>  
>  .PHONY: install
>  install:
>       $(INSTALL_DIR) $(DESTDIR)$(LIBEXEC_BIN)
>  
> -     CC="$(CC)" CFLAGS="$(PY_CFLAGS)" LDFLAGS="$(PY_LDFLAGS)" $(PYTHON) \
> -             setup.py install --record $(INSTALL_LOG) $(PYTHON_PREFIX_ARG) \
> +     CC="$(CC)" CFLAGS="$(PY_CFLAGS)" LDSHARED="$(CC)" \
> +             LDFLAGS="$(PY_LDFLAGS)" $(PYTHON) setup.py install \
> +             --record $(INSTALL_LOG) $(PYTHON_PREFIX_ARG) \
>               --root="$(DESTDIR)" --force
>  
>       $(INSTALL_PYTHON_PROG) scripts/convert-legacy-stream 
> $(DESTDIR)$(LIBEXEC_BIN)
> -- 
> 2.20.1
> 
> 
> -- 
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