diff --git a/GNUbaserules.mk b/GNUbaserules.mk
index fa8e90fd..cd66f0bc 100644
--- a/GNUbaserules.mk
+++ b/GNUbaserules.mk
@@ -1,8 +1,5 @@
 # 16 october 2015
 
-OUTDIR = out
-OBJDIR = .obj
-
 OFILES = \
 	$(subst /,_,$(CFILES)) \
 	$(subst /,_,$(MFILES)) \
diff --git a/GNUmakefile b/GNUmakefile
index f15f7450..b7dd2a24 100644
--- a/GNUmakefile
+++ b/GNUmakefile
@@ -3,6 +3,9 @@
 # silence entering/leaving messages
 MAKEFLAGS += --no-print-directory
 
+OUTDIR = out
+OBJDIR = .obj
+
 # MAME does this so :/
 ifeq ($(OS),Windows_NT)
 	OS = windows
@@ -29,10 +32,10 @@ ifndef ARCH
 endif
 
 libui:
-	@$(MAKE) -f GNUmakefile.libui OS=$(OS) ARCH=$(ARCH)
+	@$(MAKE) -f GNUmakefile.libui OS=$(OS) ARCH=$(ARCH) OUTDIR=$(OUTDIR) OBJDIR=$(OBJDIR)
 
 clean:
-	@$(MAKE) -f GNUmakefile.libui OS=$(OS) ARCH=$(ARCH) clean
+	@$(MAKE) -f GNUmakefile.libui OS=$(OS) ARCH=$(ARCH) OUTDIR=$(OUTDIR) OBJDIR=$(OBJDIR) clean
 
 test: libui
-	@$(MAKE) -f GNUmakefile.test OS=$(OS) ARCH=$(ARCH)
+	@$(MAKE) -f GNUmakefile.test OS=$(OS) ARCH=$(ARCH) OUTDIR=$(OUTDIR) OBJDIR=$(OBJDIR)
diff --git a/GNUmakefile.libui b/GNUmakefile.libui
index cc8732c5..847ce3d6 100644
--- a/GNUmakefile.libui
+++ b/GNUmakefile.libui
@@ -1,5 +1,6 @@
 # 16 october 2015
 
+include $(OS)/GNUosspecific.mk
 include common/GNUmakeinc.mk
 include $(OS)/GNUmakeinc.mk
 
@@ -12,6 +13,8 @@ NAME = libui
 CFLAGS += \
 	-fPIC
 
+SUFFIX = $(LIBSUFFIX)
+
 LDFLAGS += \
 	-shared \
 	-fPIC \
diff --git a/GNUmakefile.test b/GNUmakefile.test
index ae9d1c65..0f2c69c8 100644
--- a/GNUmakefile.test
+++ b/GNUmakefile.test
@@ -1,5 +1,6 @@
 # 16 october 2015
 
+include $(OS)/GNUosspecific.mk
 include test/GNUmakeinc.mk
 
 HFILES += \
@@ -7,35 +8,10 @@ HFILES += \
 
 NAME = test
 
-SUFFIX =
-ifeq ($(OS),windows)
-	SUFFIX = .exe
-endif
+SUFFIX = $(EXESUFFIX)
 
-# TODO split out this logic somehow
-ifeq ($(OS),windows)
-ifeq ($(ARCH),amd64)
-	ifndef CC
-		CC = x86_64-w64-mingw32-gcc
-	endif
-	ifndef RC
-		RC = x86_64-w64-mingw32-windres
-	endif
-else ifeq ($(ARCH),386)
-	ifndef CC
-		CC = i686-w64-mingw32-gcc
-	endif
-	ifndef RC
-		RC = i686-w64-mingw32-windres
-	endif
-else ifneq ($(ARCH),default)
-	$(error [FAIL] unknown architecture $(ARCH))
-endif
-	LDFLAGS += out/libui.dll
-else ifeq ($(OS),darwin)
-	LDFLAGS += out/libui.dylib
-else
-	LDFLAGS += out/libui.so
-endif
+# TODO what's the difference between doing this and linking to out/libui.so directly?
+# LDFLAGS += -L$(OUTDIR) -lui
+LDFLAGS += $(OUTDIR)/libui$(LIBSUFFIX)
 
 include GNUbaserules.mk
diff --git a/darwin/GNUmakeinc.mk b/darwin/GNUmakeinc.mk
index b6c90e6b..8f0470c2 100644
--- a/darwin/GNUmakeinc.mk
+++ b/darwin/GNUmakeinc.mk
@@ -48,5 +48,3 @@ LDFLAGS += \
 # on warning about undefined symbols:
 # the gcc flags don't work with Apple's linker
 # fortunately, we don't need any; Apple's linker warns about undefined symbols in -shared builds!
-
-SUFFIX = .dylib
diff --git a/darwin/GNUosspecific.mk b/darwin/GNUosspecific.mk
new file mode 100644
index 00000000..b38372d8
--- /dev/null
+++ b/darwin/GNUosspecific.mk
@@ -0,0 +1,4 @@
+# 16 october 2015
+
+EXESUFFIX =
+LIBSUFFIX = .dylib
diff --git a/unix/GNUmakeinc.mk b/unix/GNUmakeinc.mk
index bc920610..972c471e 100644
--- a/unix/GNUmakeinc.mk
+++ b/unix/GNUmakeinc.mk
@@ -45,5 +45,3 @@ LDFLAGS += \
 # flags for warning on undefined symbols
 LDFLAGS += \
 	-Wl,--no-undefined -Wl,--no-allow-shlib-undefined
-
-SUFFIX = .so
diff --git a/unix/GNUosspecific.mk b/unix/GNUosspecific.mk
new file mode 100644
index 00000000..0e2a497c
--- /dev/null
+++ b/unix/GNUosspecific.mk
@@ -0,0 +1,4 @@
+# 16 october 2015
+
+EXESUFFIX =
+LIBSUFFIX = .so
diff --git a/windows/GNUmakeinc.mk b/windows/GNUmakeinc.mk
index f2aa682e..06f54ccf 100644
--- a/windows/GNUmakeinc.mk
+++ b/windows/GNUmakeinc.mk
@@ -56,23 +56,3 @@ LDFLAGS += \
 # warnings on undefined symbols
 LDFLAGS += \
 	-Wl,--no-undefined -Wl,--no-allow-shlib-undefined
-
-SUFFIX = .dll
-
-ifeq ($(ARCH),amd64)
-	ifndef CC
-		CC = x86_64-w64-mingw32-gcc
-	endif
-	ifndef RC
-		RC = x86_64-w64-mingw32-windres
-	endif
-else ifeq ($(ARCH),386)
-	ifndef CC
-		CC = i686-w64-mingw32-gcc
-	endif
-	ifndef RC
-		RC = i686-w64-mingw32-windres
-	endif
-else ifneq ($(ARCH),default)
-	$(error [FAIL] unknown architecture $(ARCH))
-endif
diff --git a/windows/GNUosspecific.mk b/windows/GNUosspecific.mk
new file mode 100644
index 00000000..50512181
--- /dev/null
+++ b/windows/GNUosspecific.mk
@@ -0,0 +1,22 @@
+# 16 october 2015
+
+EXESUFFIX = .exe
+LIBSUFFIX = .dll
+
+ifeq ($(ARCH),amd64)
+	ifndef CC
+		CC = x86_64-w64-mingw32-gcc
+	endif
+	ifndef RC
+		RC = x86_64-w64-mingw32-windres
+	endif
+else ifeq ($(ARCH),386)
+	ifndef CC
+		CC = i686-w64-mingw32-gcc
+	endif
+	ifndef RC
+		RC = i686-w64-mingw32-windres
+	endif
+else ifneq ($(ARCH),default)
+	$(error [FAIL] unknown architecture $(ARCH))
+endif