diff --git a/.github/workflows/c-cpp.yml b/.github/workflows/c-cpp.yml
index 0b3e83d57..9cbebb3f9 100644
--- a/.github/workflows/c-cpp.yml
+++ b/.github/workflows/c-cpp.yml
@@ -7,17 +7,23 @@ on:
   pull_request:
     branches:
       - "*"
+  workflow_dispatch:
+    inputs:
+      debug_enabled:
+        description: 'Run the build with tmate debugging enabled (https://github.com/marketplace/actions/debugging-with-tmate)'     
+        required: false
+        default: false
 
 jobs:
   build:
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
     steps:
-    - name: install-mingw
+    - name: Install MinGW
       run: "sudo apt-get install gcc-mingw-w64-i686"
     - uses: actions/checkout@v2
     - name: make
       run: make zip
-    - name: succ
+    - name: Work around silly artifact uploader
       run: unzip flexptools.zip -d flexptools-zip
     - run: unzip spin2cpp.zip -d spin2cpp-zip
     - uses: actions/upload-artifact@v2.1.3
@@ -29,10 +35,20 @@ jobs:
         name: spin2cpp-git
         path: "spin2cpp-zip/*"
   test:
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
     steps:
-     - uses: actions/checkout@v2
-     - name: make
-       run: make
-     - name: test
-       run: make test_offline
+    - uses: actions/checkout@v2
+    # Enable tmate debugging of manually-triggered workflows if the input option was provided
+    - name: Setup tmate session
+      uses: mxschmitt/action-tmate@v3
+      if: ${{ github.event_name == 'workflow_dispatch' && github.event.inputs.debug_enabled }}
+    - name: Install non-buggy GCC/GCOV
+      run: "sudo apt-get install gcc-8"
+    - name: make
+      run: make all TEST_COVERAGE=1 CC=gcc-8 CCOV=gcov-8
+    - name: test
+      run: make test_offline TEST_COVERAGE=1 CC=gcc-8 CCOV=gcov-8
+    - name: gcov
+      run: make coverage TEST_COVERAGE=1 CC=gcc-8 CCOV=gcov-8
+    - name: Upload coverage
+      run: "bash <(curl -s https://codecov.io/bash) -X gcov"
diff --git a/Makefile b/Makefile
index d3eca7c0a..b50ea8640 100644
--- a/Makefile
+++ b/Makefile
@@ -68,16 +68,29 @@ else ifeq ($(CROSS),macosx)
   CC=o64-clang -DMACOSX -O
   EXT=
   BUILD=./build-macosx
-else ifeq ($(OS),Windows_NT)
-  CC=gcc
+else ifeq ($(OS),Windows_NT)	
+  ifeq ($(CC),cc)
+    # Workaround for weird windows/mingw/msys/whatever nonsense
+	CC=gcc
+  endif
+  CC?=gcc
   EXT=.exe
   BUILD=./build
 else
-  CC=gcc
+  CC?=gcc
   EXT=
   BUILD=./build
 endif
 
+CCOV?=gcov
+
+ifdef TEST_COVERAGE
+	BUILD=./build-gcov
+	CFLAGS+=--coverage -fprofile-dir=$(realpath .) -fprofile-abs-path
+endif
+
+export BUILD
+
 INC=-I. -I$(BUILD)
 DEFS=-DFLEXSPIN_BUILD
 
@@ -106,9 +119,9 @@ endif
 #check:
 #	echo YACC="$(RUNYACC)" YACCVER="$(YACCVER)" YACC_CHECK="$(YACC_CHECK)"
 
-CFLAGS = -g -Wall $(INC) $(DEFS)
-#CFLAGS = -no-pie -pg -Wall $(INC) $(DEFS)
-#CFLAGS = -g -Og -Wall -Wc++-compat -Werror $(INC) $(DEFS)
+CFLAGS += -g -Wall $(INC) $(DEFS)
+#CFLAGS += -no-pie -pg -Wall $(INC) $(DEFS)
+#CFLAGS += -g -Og -Wall -Wc++-compat -Werror $(INC) $(DEFS)
 LIBS = -lm
 RM = rm -rf
 
@@ -151,7 +164,7 @@ help:
 
 all: $(BUILD) $(PROGS)
 
-$(BUILD)/testlex$(EXT): testlex.c $(LEXOBJS)
+$(BUILD)/testlex$(EXT): $(LEXOBJS) $(BUILD)/testlex.o
 	$(CC) $(CFLAGS) -o $@ $^ $(LIBS)
 
 $(BUILD)/spin.tab.c $(BUILD)/spin.tab.h: frontends/spin/spin.y
@@ -172,10 +185,16 @@ preproc: preprocess.c $(UTIL)
 clean:
 	$(RM) $(PROGS) $(BUILD)/* *.zip
 
-test_offline: lextest asmtest cpptest errtest p2test
+clean_profile:
+	$(RM) $(BUILD)/*.gcda $(BUILD)/*.gcov
+
+test_offline: $(BUILD) lextest asmtest cpptest errtest p2test
 test: test_offline runtest
 #test: lextest asmtest cpptest errtest runtest
 
+coverage: 
+	(cd $(BUILD); $(CCOV) testlex.c cmdline.c spin2cpp.c flexspin.c flexcc.c $(SPINSRCS))
+
 lextest: $(PROGS)
 	$(BUILD)/testlex
 
@@ -194,13 +213,13 @@ p2test: $(PROGS)
 runtest: $(PROGS)
 	(cd Test; ./runtests.sh)
 
-$(BUILD)/spin2cpp$(EXT): spin2cpp.c cmdline.c $(OBJS)
+$(BUILD)/spin2cpp$(EXT): $(BUILD)/spin2cpp.o $(BUILD)/cmdline.o $(OBJS)
 	$(CC) $(CFLAGS) -o $@ $^ $(LIBS)
 
-$(BUILD)/flexspin$(EXT): flexspin.c cmdline.c $(OBJS)
+$(BUILD)/flexspin$(EXT): $(BUILD)/flexspin.o $(BUILD)/cmdline.o $(OBJS)
 	$(CC) $(CFLAGS) -o $@ $^ $(LIBS)
 
-$(BUILD)/flexcc$(EXT): flexcc.c cmdline.c $(OBJS)
+$(BUILD)/flexcc$(EXT): $(BUILD)/flexcc.o $(BUILD)/cmdline.o $(OBJS)
 	$(CC) $(CFLAGS) -o $@ $^ $(LIBS)
 
 $(BUILD):
diff --git a/Test/asmtests.sh b/Test/asmtests.sh
index 5e85dd8c4..5421759eb 100755
--- a/Test/asmtests.sh
+++ b/Test/asmtests.sh
@@ -3,7 +3,7 @@
 if [ "$1" != "" ]; then
   SPIN2CPP=$1
 else
-  SPIN2CPP=../build/spin2cpp
+  SPIN2CPP=../${BUILD:='./build'}/spin2cpp
 fi
 
 PROG="$SPIN2CPP -I../Lib"
diff --git a/Test/cpptests.sh b/Test/cpptests.sh
index ce81c3c9f..165dd7ff4 100755
--- a/Test/cpptests.sh
+++ b/Test/cpptests.sh
@@ -3,7 +3,7 @@
 if [ "$1" != "" ]; then
   SPIN2CPP=$1
 else
-  SPIN2CPP=../build/spin2cpp
+  SPIN2CPP=../${BUILD:='./build'}/spin2cpp
 fi
 
 PROG="$SPIN2CPP -I../Lib"
diff --git a/Test/errtests.sh b/Test/errtests.sh
index 06421d2cc..266c4b65c 100755
--- a/Test/errtests.sh
+++ b/Test/errtests.sh
@@ -3,7 +3,7 @@
 if [ "$1" != "" ]; then
   PROG=$1
 else
-  PROG=../build/spin2cpp
+  PROG=../${BUILD:='./build'}/spin2cpp
 fi
 CC=propeller-elf-gcc
 ok="ok"
diff --git a/Test/p2bin.sh b/Test/p2bin.sh
index fce123b71..0234f78b2 100755
--- a/Test/p2bin.sh
+++ b/Test/p2bin.sh
@@ -3,7 +3,7 @@
 if [ "$1" != "" ]; then
   FASTSPIN=$1
 else
-  FASTSPIN=../build/flexspin
+  FASTSPIN=../${BUILD:='./build'}/flexspin
 fi
 
 PROG="$FASTSPIN -q -2b -I../Lib"
diff --git a/Test/runtests.sh b/Test/runtests.sh
index 741e9ae26..6c3f1d426 100755
--- a/Test/runtests.sh
+++ b/Test/runtests.sh
@@ -4,8 +4,8 @@ if [ "$1" != "" ]; then
     SPIN2CPP=$1
     FASTSPIN="$1 --asm --binary --code=hub"
 else
-    SPIN2CPP=../build/spin2cpp
-    FASTSPIN="../build/flexspin -g -q"
+    SPIN2CPP=../${BUILD:='./build'}/spin2cpp
+    FASTSPIN="../${BUILD:='./build'}/flexspin -g -q"
 fi
 
 PROG_C="$SPIN2CPP -I../Lib"
diff --git a/Test/runtests_bc.sh b/Test/runtests_bc.sh
index fb5e77217..26923ca1a 100755
--- a/Test/runtests_bc.sh
+++ b/Test/runtests_bc.sh
@@ -4,8 +4,8 @@ if [ "$1" != "" ]; then
     SPIN2CPP=$1
     FASTSPIN="$1 -g -q --interp=rom"
 else
-    SPIN2CPP=../build/spin2cpp
-    FASTSPIN="../build/flexspin -g -q --interp=rom"
+    SPIN2CPP=../${BUILD:='./build'}/spin2cpp
+    FASTSPIN="../${BUILD:='./build'}/flexspin -g -q --interp=rom"
 fi
 
 PROG_ASM="$FASTSPIN -I../Lib"
diff --git a/Test/runtests_p2.sh b/Test/runtests_p2.sh
index 5a9c476ba..7c8f855e2 100755
--- a/Test/runtests_p2.sh
+++ b/Test/runtests_p2.sh
@@ -4,8 +4,8 @@ if [ "$1" != "" ]; then
     SPIN2CPP=$1
     FASTSPIN="$1 --asm --binary --code=hub"
 else
-    SPIN2CPP=../build/spin2cpp
-    FASTSPIN="../build/flexspin -2 -O2 -g -q"
+    SPIN2CPP=../${BUILD:='./build'}/spin2cpp
+    FASTSPIN="../${BUILD:='./build'}/flexspin -2 -O2 -g -q"
 fi
 
 PROG_C="$SPIN2CPP -I../Lib"