configure: Honour --disable-werror for Sphinx

If we are not making warnings fatal for compilation, make them
non-fatal when building the Sphinx documentation also.  (For instance
Sphinx 3.0 warns about some constructs that older versions were happy
with, which is a build failure if we use the warnings-as-errors

This provides a workaround at least for LP:1872113.

Signed-off-by: Peter Maydell <>
Reviewed-by: Richard Henderson <>
Reviewed-by: Alex Bennée <>
diff --git a/Makefile b/Makefile
index 84ef881..8a9113e 100644
--- a/Makefile
+++ b/Makefile
@@ -1076,7 +1076,7 @@
 # Note the use of different doctree for each (manual, builder) tuple;
 # this works around Sphinx not handling parallel invocation on
 # a single doctree:
-build-manual = $(call quiet-command,CONFDIR="$(qemu_confdir)" $(SPHINX_BUILD) $(if $(V),,-q) -W -b $2 -D version=$(VERSION) -D release="$(FULL_VERSION)" -d .doctrees/$1-$2 $(SRC_PATH)/docs/$1 $(MANUAL_BUILDDIR)/$1 ,"SPHINX","$(MANUAL_BUILDDIR)/$1")
+build-manual = $(call quiet-command,CONFDIR="$(qemu_confdir)" $(SPHINX_BUILD) $(if $(V),,-q) $(SPHINX_WERROR) -b $2 -D version=$(VERSION) -D release="$(FULL_VERSION)" -d .doctrees/$1-$2 $(SRC_PATH)/docs/$1 $(MANUAL_BUILDDIR)/$1 ,"SPHINX","$(MANUAL_BUILDDIR)/$1")
 # We assume all RST files in the manual's directory are used in it
 manual-deps = $(wildcard $(SRC_PATH)/docs/$1/*.rst $(SRC_PATH)/docs/$1/*/*.rst) \
               $(SRC_PATH)/docs/ \
diff --git a/configure b/configure
index 233c671..9b1f5b3 100755
--- a/configure
+++ b/configure
@@ -4928,6 +4928,12 @@
+# If we're making warnings fatal, apply this to Sphinx runs as well
+if test "$werror" = "yes"; then
+    sphinx_werror="-W"
 # Check we have a new enough version of sphinx-build
 has_sphinx_build() {
     # This is a bit awkward but works: create a trivial document and
@@ -4936,7 +4942,7 @@
     # sphinx-build doesn't exist at all or if it is too old.
     mkdir -p "$TMPDIR1/sphinx"
     touch "$TMPDIR1/sphinx/index.rst"
-    "$sphinx_build" -c "$source_path/docs" -b html "$TMPDIR1/sphinx" "$TMPDIR1/sphinx/out" >/dev/null 2>&1
+    "$sphinx_build" $sphinx_werror -c "$source_path/docs" -b html "$TMPDIR1/sphinx" "$TMPDIR1/sphinx/out" >/dev/null 2>&1
 # Check if tools are available to build documentation.
@@ -7631,6 +7637,7 @@
 echo "INSTALL_LIB=$install -c -m 0644" >> $config_host_mak
 echo "PYTHON=$python" >> $config_host_mak
 echo "SPHINX_BUILD=$sphinx_build" >> $config_host_mak
+echo "SPHINX_WERROR=$sphinx_werror" >> $config_host_mak
 echo "GENISOIMAGE=$genisoimage" >> $config_host_mak
 echo "CC=$cc" >> $config_host_mak
 if $iasl -h > /dev/null 2>&1; then