I think it would be better to set it all the time, like MODSIMPLE_configure 
does in bsd.port.mk.

-- 
  Sent from a phone, apologies for poor formatting.

On 4 September 2026 18:56:52 Klemens Nanni <kn@openbsd.org> wrote:

> graphics/py-matplotlib with MODPY_PYBUILD=mesonpy via
>
>  /usr/local/lib/python3.14/site-packages/mesonbuild/envconfig.py:        
>  return ExternalProgram('sccache', silent=True)
>
> detects /usr/local/bin/sccache and uses that over default "c++",
> leading to build failure with PORTS_PRIVSEP=yes:
>
>  sccache: error: failed to create directory 
>  `/py-matplotlib-3.10.8_writes_to_HOME/.cache/sccache/preprocessor`: 
>  Permission denied (os error 13)
>
> Environmental CXX takes priority, but is not set compared to CC,
> which is how I tracked this down not knowing anything about how
> Python builds C++ code.
>
> Setting CXX where CC comes from fixes it and seems safe.
>
> tb@ mentioned COMPILER_LANGS, but I don't fully understand the
> implications of having CXX in the environment for Python ports
> doing COMPILER_LANGS=C (if they exist), so I just gated it.
>
> This fixes matplotlib for me when sccache is installed.
>
> Feedback? OK?
>
>
> Index: python.port.mk
> ===================================================================
> RCS file: /cvs/ports/lang/python/3/python.port.mk,v
> diff -u -p -r1.28 python.port.mk
> --- python.port.mk	19 Jun 2026 13:49:04 -0000	1.28
> +++ python.port.mk	4 Sep 2026 16:56:30 -0000
> @@ -224,6 +224,9 @@ MODPY_DISTUTILS_INSTALL ?=	install --pre
> 				--root=${DESTDIR}
>
> MAKE_ENV +=		CC=${CC}
> +.if ${COMPILER_LANGS:Mc++}
> +MAKE_ENV +=		CXX=${CXX}
> +.endif
> CONFIGURE_ENV +=	PYTHON="${MODPY_BIN}"
> .if ${CONFIGURE_STYLE:Mgnu}
> CONFIGURE_ENV +=	ac_cv_prog_PYTHON="${MODPY_BIN}" \