pango won't build, issue with clang ? (OSX BigSur, Xcode 13.2.1 )

[jamesstuartgunning (James Gunning)]

% port upgrade outdated fails on pango @1.50.7_0+quartz+x11

Relevant chunk of /opt/local/var/macports/logs/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_x11_pango/pango/main.log is:

:info:build [39/151] /usr/bin/clang -Ipango/libpangoft2-1.0.0.dylib.p -Ipango -I../pango-1.50.7/pango -I. -I../pango-1.50.7 -I/opt/local/include/glib-2.0 -I/opt/local/lib/glib-2.0/include -I/opt/local/include/fribidi -I/opt/local/include/harfbuzz -I/opt/local/include/freetype2 -I/opt/local/include/libpng16 -I/opt/X11/include -I/opt/X11/include/cairo -I/opt/local/include/pixman-1 -I/opt/local/include -fcolor-diagnostics -Wall -Winvalid-pch -std=gnu99 -O2 -g -D_POSIX_C_SOURCE=200809L -D_POSIX_THREAD_SAFE_FUNCTIONS -D_GNU_SOURCE -pipe -Os -Wno-error,-Wimplicit-fallthrough -isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX11.sdk -arch x86_64 -isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX11.sdk -DPANGO_ENABLE_DEBUG '-DG_LOG_DOMAIN="Pango"' -DG_LOG_USE_STRUCTURED=1 -DPANGO_COMPILATION '-DSYSCONFDIR="/opt/local/etc"' '-DLIBDIR="/opt/local/lib"' -DPANGO_DISABLE_DEPRECATION_WARNINGS -MD -MQ pango/libpangoft2-1.0.0.dylib.p/pangofc-fontmap.c.o -MF pango/libpangoft2-1.0.0.dylib.p/pangofc-fontmap.c.o.d -o pango/libpangoft2-1.0.0.dylib.p/pangofc-fontmap.c.o -c ../pango-1.50.7/pango/pangofc-fontmap.c
:info:build FAILED: pango/libpangoft2-1.0.0.dylib.p/pangofc-fontmap.c.o 
:info:build /usr/bin/clang -Ipango/libpangoft2-1.0.0.dylib.p -Ipango -I../pango-1.50.7/pango -I. -I../pango-1.50.7 -I/opt/local/include/glib-2.0 -I/opt/local/lib/glib-2.0/include -I/opt/local/include/fribidi -I/opt/local/include/harfbuzz -I/opt/local/include/freetype2 -I/opt/local/include/libpng16 -I/opt/X11/include -I/opt/X11/include/cairo -I/opt/local/include/pixman-1 -I/opt/local/include -fcolor-diagnostics -Wall -Winvalid-pch -std=gnu99 -O2 -g -D_POSIX_C_SOURCE=200809L -D_POSIX_THREAD_SAFE_FUNCTIONS -D_GNU_SOURCE -pipe -Os -Wno-error,-Wimplicit-fallthrough -isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX11.sdk -arch x86_64 -isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX11.sdk -DPANGO_ENABLE_DEBUG '-DG_LOG_DOMAIN="Pango"' -DG_LOG_USE_STRUCTURED=1 -DPANGO_COMPILATION '-DSYSCONFDIR="/opt/local/etc"' '-DLIBDIR="/opt/local/lib"' -DPANGO_DISABLE_DEPRECATION_WARNINGS -MD -MQ pango/libpangoft2-1.0.0.dylib.p/pangofc-fontmap.c.o -MF pango/libpangoft2-1.0.0.dylib.p/pangofc-fontmap.c.o.d -o pango/libpangoft2-1.0.0.dylib.p/pangofc-fontmap.c.o -c ../pango-1.50.7/pango/pangofc-fontmap.c
:info:build warning: unknown -Werror warning specifier: '-Wno-error,-Wimplicit-fallthrough' [-Wunknown-warning-option]
**:info:build ../pango-1.50.7/pango/pangofc-fontmap.c:1684:43: error: use of undeclared identifier 'FC_VARIABLE'**
:info:build                                           FC_VARIABLE,
:info:build                                           ^
:info:build ../pango-1.50.7/pango/pangofc-fontmap.c:1728:63: error: use of undeclared identifier 'FC_VARIABLE'
:info:build               variable = FcPatternGetBool (fontset->fonts[i], FC_VARIABLE, 0, &variable);

It may be a clang issue with not implementing/using -Wno-error,-Wimplicit-fallthrough ?

% /usr/bin/clang -v
Apple clang version 13.0.0 (clang-1300.0.29.30)
Target: x86_64-apple-darwin20.6.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin