diff --git a/Makefile b/Makefile
index 49f05be43..bba865fe0 100644
--- a/Makefile
+++ b/Makefile
@@ -85,6 +85,7 @@ PKGS =
 
 -include ~/.cosmo.mk
 include build/functions.mk			#─┐
+include build/compiler.mk			#─┐
 include build/definitions.mk			# ├──META
 include build/config.mk				# │  You can build
 include build/rules.mk				# │  You can topologically order
diff --git a/build/compiler.mk b/build/compiler.mk
new file mode 100644
index 000000000..c641d684c
--- /dev/null
+++ b/build/compiler.mk
@@ -0,0 +1,43 @@
+#-*-mode:makefile-gmake;indent-tabs-mode:t;tab-width:8;coding:utf-8-*-┐
+#───vi: set et ft=make ts=8 tw=8 fenc=utf-8 :vi───────────────────────┘
+#
+# SYNOPSIS
+#
+#   Cosmopolitan Compiler and Toold Definitions
+#
+
+# see build/compile, etc. which run third_party/gcc/unbundle.sh
+AR = build/bootstrap/ar.com
+PKG = build/bootstrap/package.com
+MKDEPS = build/bootstrap/mkdeps.com
+ZIPOBJ = build/bootstrap/zipobj.com
+
+ifeq ($(MODE), darwin)
+TOOLPREFIX=/usr/local/bin/x86_64-linux-musl-
+AS = $(TOOLPREFIX)as
+CC = $(TOOLPREFIX)gcc
+CXX = $(TOOLPREFIX)g++
+CXXFILT = $(TOOLPREFIX)c++filt
+LD = $(TOOLPREFIX)ld.bfd
+NM = $(TOOLPREFIX)nm
+GCC = $(TOOLPREFIX)gcc
+STRIP = $(TOOLPREFIX)strip
+OBJCOPY = $(TOOLPREFIX)objcopy
+OBJDUMP = $(TOOLPREFIX)ojbdump
+ADDRLINE = $(TOOLPREFIX)addr2line
+
+else
+
+AS = o/third_party/gcc/bin/x86_64-linux-musl-as
+CC = o/third_party/gcc/bin/x86_64-linux-musl-gcc
+CXX = o/third_party/gcc/bin/x86_64-linux-musl-g++
+CXXFILT = o/third_party/gcc/bin/x86_64-linux-musl-c++filt
+LD = o/third_party/gcc/bin/x86_64-linux-musl-ld.bfd
+NM = o/third_party/gcc/bin/x86_64-linux-musl-nm
+GCC = o/third_party/gcc/bin/x86_64-linux-musl-gcc
+STRIP = o/third_party/gcc/bin/x86_64-linux-musl-strip
+OBJCOPY = o/third_party/gcc/bin/x86_64-linux-musl-objcopy
+OBJDUMP = o/third_party/gcc/bin/x86_64-linux-musl-objdump
+ADDR2LINE = $(shell pwd)/o/third_party/gcc/bin/x86_64-linux-musl-addr2line
+
+endif
diff --git a/build/config.mk b/build/config.mk
index 17827a02e..427b8b8ce 100644
--- a/build/config.mk
+++ b/build/config.mk
@@ -308,6 +308,23 @@ OBJDUMP = llvm-objdump
 ADDR2LINE = llvm-addr2line
 endif
 
+# macOS using gcc - options copied from Tiny Metallic Unix Mode
+ifeq ($(MODE), darwin)
+CONFIG_CPPFLAGS +=		\
+	-DTINY			\
+	-DNDEBUG		\
+	-DTRUSTWORTHY		\
+	-DSUPPORT_VECTOR=251
+CONFIG_CCFLAGS +=		\
+	-Os			\
+	-fno-align-functions	\
+	-fno-align-jumps	\
+	-fno-align-labels	\
+	-fno-align-loops
+TARGET_ARCH ?=			\
+	-msse3
+endif
+
 # ANSI Mode
 #
 # These flags cause GCC to predefine __STRICT_ANSI__. Please be warned
diff --git a/build/definitions.mk b/build/definitions.mk
index 7a08e72a7..e7310250d 100644
--- a/build/definitions.mk
+++ b/build/definitions.mk
@@ -54,23 +54,6 @@ GZ ?= gzip
 CLANG = clang
 FC = gfortran  #/opt/cross9f/bin/x86_64-linux-musl-gfortran
 
-# see build/compile, etc. which run third_party/gcc/unbundle.sh
-AR = build/bootstrap/ar.com
-PKG = build/bootstrap/package.com
-MKDEPS = build/bootstrap/mkdeps.com
-ZIPOBJ = build/bootstrap/zipobj.com
-AS = o/third_party/gcc/bin/x86_64-linux-musl-as
-CC = o/third_party/gcc/bin/x86_64-linux-musl-gcc
-CXX = o/third_party/gcc/bin/x86_64-linux-musl-g++
-CXXFILT = o/third_party/gcc/bin/x86_64-linux-musl-c++filt
-LD = o/third_party/gcc/bin/x86_64-linux-musl-ld.bfd
-NM = o/third_party/gcc/bin/x86_64-linux-musl-nm
-GCC = o/third_party/gcc/bin/x86_64-linux-musl-gcc
-STRIP = o/third_party/gcc/bin/x86_64-linux-musl-strip
-OBJCOPY = o/third_party/gcc/bin/x86_64-linux-musl-objcopy
-OBJDUMP = o/third_party/gcc/bin/x86_64-linux-musl-objdump
-ADDR2LINE = $(shell pwd)/o/third_party/gcc/bin/x86_64-linux-musl-addr2line
-
 COMMA := ,
 PWD := $(shell pwd)
 IMAGE_BASE_VIRTUAL ?= 0x400000
diff --git a/build/getccversion b/build/getccversion
index ed74ba39a..f0bc8cf86 100755
--- a/build/getccversion
+++ b/build/getccversion
@@ -18,8 +18,10 @@
 #   links GCC runtimes when using later versions, so some concerns might
 #   not apply.
 
-if [ ! -d o/third_party/gcc ]; then
-  third_party/gcc/unbundle.sh
+if [ x`uname -s` != xDarwin ]; then
+    if [ ! -d o/third_party/gcc ]; then
+      third_party/gcc/unbundle.sh
+    fi
 fi
 
 set -e
diff --git a/build/sanitycheck b/build/sanitycheck
index c2da2d263..235d10af4 100755
--- a/build/sanitycheck
+++ b/build/sanitycheck
@@ -9,7 +9,7 @@
 #   This script is launched at the start of Makefile to detect if
 #   binfmt_misc was tuned to launch 'MZ' shell scripts under WINE
 
-if [ x`uname -s` != xLinux ]; then
+if [ x`uname -s` != xLinux -a x`uname -s` != xDarwin ]; then
   cat <<'EOF' >&2
 
 ERROR
diff --git a/test/libc/release/emulate.sh b/test/libc/release/emulate.sh
index cb9152877..416450c12 100755
--- a/test/libc/release/emulate.sh
+++ b/test/libc/release/emulate.sh
@@ -8,6 +8,10 @@ if [ "$MODE" = opt ] || [ "$MODE" = optlinux ]; then
   exit
 fi
 
+if [ "$MODE" = darwin ]; then
+  exit  # TODO
+fi
+
 # smoke test userspace binary emulation
 CMD="o/$MODE/tool/build/blinkenlights.com.dbg o/$MODE/examples/hello.com"
 if OUTPUT="$($CMD)"; then
diff --git a/tool/build/compile.c b/tool/build/compile.c
index a30df1e30..164c99676 100644
--- a/tool/build/compile.c
+++ b/tool/build/compile.c
@@ -946,7 +946,9 @@ int main(int argc, char *argv[]) {
       AddArg("-Wno-unused-command-line-argument");
       AddArg("-Wno-incompatible-pointer-types-discards-qualifiers");
     }
-    AddArg("-no-canonical-prefixes");
+    if (!IsXnu()) {
+      AddArg("-no-canonical-prefixes");
+    }
     if (!__nocolor) {
       AddArg(firstnonnull(colorflag, "-fdiagnostics-color=always"));
     }