[gentoo-dev] [PATCH] cmake.eclass: workaround S=${WORKDIR} creating builddir above ${WORKDIR}

[Sam James <sam@gentoo.org>]

When S=${WORKDIR}, cmake.eclass would create its build directory (if CMAKE_USE_DIR
is unset) above WORKDIR(!) as ${WORKDIR}_build. Creating directories above
WORKDIR is not legal.

Portage has its own bug (bug #889418) in that it doesn't clean up unknown directories
above WORKDIR in PORTAGE_TMPDIR, so combined, you get a problem where "ebuild ... clean" doesn't
actually clean things up at all, and you get very confusing issues if e.g. changing
CC between runs.

The explicit S=WORKDIR check isn't truly needed but it makes explicit our
intent here.

Bug: https://bugs.gentoo.org/889418
Closes: https://bugs.gentoo.org/889420
Signed-off-by: Sam James <sam@gentoo.org>
---
 eclass/cmake.eclass | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/eclass/cmake.eclass b/eclass/cmake.eclass
index 1cdbc123a243..4050beb22ba3 100644
--- a/eclass/cmake.eclass
+++ b/eclass/cmake.eclass
@@ -293,6 +293,15 @@ _cmake_check_build_dir() {
 		BUILD_DIR="${CMAKE_USE_DIR}"
 	else
 		: "${BUILD_DIR:=${CMAKE_USE_DIR}_build}"
+
+		# Avoid creating ${WORKDIR}_build (which is above WORKDIR).
+		# TODO: For EAPI > 8, we should ban S=WORKDIR for CMake.
+		# See bug #889420.
+		if [[ ${S} == ${WORKDIR} && ${BUILD_DIR} == ${WORKDIR}_build ]] ; then
+			eqawarn "QA notice: S=WORKDIR is deprecated for cmake.eclass."
+			eqawarn "Please relocate the sources in src_unpack."
+			BUILD_DIR="${WORKDIR}"/${P}_build
+		fi
 	fi
 
 	einfo "Source directory (CMAKE_USE_DIR): \"${CMAKE_USE_DIR}\""
-- 
2.41.0