diff --git a/Makefile b/Makefile
index 776e49a79..b69ddd2ad 100644
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,6 @@
 
-CONFIG := clang
+CONFIG := none
+# CONFIG := clang
 # CONFIG := gcc
 # CONFIG := afl-gcc
 # CONFIG := emcc
@@ -217,7 +218,7 @@ endif
 ifeq ($(CONFIG),clang)
 CXX = clang++
 CXXFLAGS += -std=$(CXXSTD) -Os
-ABCMKARGS += ARCHFLAGS="-DABC_USE_STDINT_H -Wno-c++11-narrowing $(ABC_ARCHFLAGS)"
+ABCMKARGS += ARCHFLAGS="-DABC_USE_STDINT_H $(ABC_ARCHFLAGS)"
 
 ifneq ($(SANITIZER),)
 $(info [Clang Sanitizer] $(SANITIZER))
@@ -265,7 +266,7 @@ ABCMKARGS += ARCHFLAGS="-DABC_USE_STDINT_H"
 else ifeq ($(CONFIG),emcc)
 CXX = emcc
 CXXFLAGS := -std=$(CXXSTD) $(filter-out -fPIC -ggdb,$(CXXFLAGS))
-ABCMKARGS += ARCHFLAGS="-DABC_USE_STDINT_H -DABC_MEMALIGN=8 -Wno-c++11-narrowing"
+ABCMKARGS += ARCHFLAGS="-DABC_USE_STDINT_H -DABC_MEMALIGN=8"
 EMCC_CXXFLAGS := -Os -Wno-warn-absolute-paths
 EMCC_LINKFLAGS := --embed-file share
 EMCC_LINKFLAGS += -s NO_EXIT_RUNTIME=1
@@ -317,7 +318,7 @@ CXXFLAGS := $(WASIFLAGS) -std=$(CXXSTD) -Os -D_WASI_EMULATED_PROCESS_CLOCKS $(fi
 LINKFLAGS := $(WASIFLAGS) -Wl,-z,stack-size=1048576 $(filter-out -rdynamic,$(LINKFLAGS))
 LIBS := -lwasi-emulated-process-clocks $(filter-out -lrt,$(LIBS))
 ABCMKARGS += AR="$(AR)" RANLIB="$(RANLIB)"
-ABCMKARGS += ARCHFLAGS="$(WASIFLAGS) -D_WASI_EMULATED_PROCESS_CLOCKS -DABC_USE_STDINT_H -DABC_NO_DYNAMIC_LINKING -DABC_NO_RLIMIT -Wno-c++11-narrowing"
+ABCMKARGS += ARCHFLAGS="$(WASIFLAGS) -D_WASI_EMULATED_PROCESS_CLOCKS -DABC_USE_STDINT_H -DABC_NO_DYNAMIC_LINKING -DABC_NO_RLIMIT"
 ABCMKARGS += OPTFLAGS="-Os"
 EXE = .wasm
 
@@ -360,8 +361,12 @@ ABCMKARGS += ARCHFLAGS="-DABC_USE_STDINT_H -DWIN32_NO_DLL -DHAVE_STRUCT_TIMESPEC
 ABCMKARGS += LIBS="-lpthread -lshlwapi -s" ABC_USE_NO_READLINE=0 CC="x86_64-w64-mingw32-gcc" CXX="$(CXX)"
 EXE = .exe
 
-else ifneq ($(CONFIG),none)
-$(error Invalid CONFIG setting '$(CONFIG)'. Valid values: clang, gcc, emcc, mxe, msys2-32, msys2-64)
+else ifeq ($(CONFIG),none)
+CXXFLAGS += -std=$(CXXSTD) -Os
+ABCMKARGS += ARCHFLAGS="-DABC_USE_STDINT_H $(ABC_ARCHFLAGS)"
+
+else
+$(error Invalid CONFIG setting '$(CONFIG)'. Valid values: clang, gcc, emcc, mxe, msys2-32, msys2-64, none)
 endif
 
 ifeq ($(ENABLE_LIBYOSYS),1)
@@ -1127,6 +1132,9 @@ echo-git-rev:
 echo-abc-rev:
 	@echo "$(ABCREV)"
 
+echo-cxx:
+	@echo "$(CXX)"
+
 -include libs/*/*.d
 -include frontends/*/*.d
 -include passes/*/*.d
diff --git a/README.md b/README.md
index c330d4f74..4647efbe9 100644
--- a/README.md
+++ b/README.md
@@ -105,11 +105,17 @@ For Cygwin use the following command to install all prerequisites, or select the
 
 	setup-x86_64.exe -q --packages=bison,flex,gcc-core,gcc-g++,git,libffi-devel,libreadline-devel,make,pkg-config,python3,tcl-devel,boost-build,zlib-devel
 
-To configure the build system to use a specific compiler, use one of
+The environment variable `CXX` can be used to control the C++ compiler used, or
+run one of the following:
 
 	$ make config-clang
 	$ make config-gcc
 
+Note that these will result in `make` ignoring the `CXX` environment variable,
+unless `CXX` is assigned in the call to make, e.g.
+
+  $ make CXX=$CXX
+
 For other compilers and build configurations it might be
 necessary to make some changes to the config section of the
 Makefile.