Restore environment from parent for external processes

Makefile

@@ -2,20 +2,37 @@ CFLAGS ?= -O2 -Wall -Wextra
 LDFLAGS += -s
 BIN = AppRun_patched
 LIB = exec.so
+EXEC_TEST = exec_test
+ENV_TEST = env_test
 
+checkrt: $(BIN) $(LIB)
 
-all: $(BIN) $(LIB)
+test: $(EXEC_TEST) $(ENV_TEST)
+
+all: checkrt test
 
 clean:
-	-rm -f $(BIN) $(LIB) *.o AppRun.c AppRun_patched.c
+	-rm -f $(BIN) $(LIB) $(EXEC_TEST) $(ENV_TEST) *.o AppRun.c AppRun_patched.c
 
-$(BIN): AppRun_patched.o checkrt.o
+$(BIN): AppRun_patched.o checkrt.o env.o
 
-$(LIB): exec.o
+$(LIB): exec.o env.o
 	$(CC) -shared $(LDFLAGS) -o $@ $^ -ldl
 
 AppRun_patched.o checkrt.o: CFLAGS += -include checkrt.h
-exec.o: CFLAGS += -fPIC -std=c99
+exec.o env.o: CFLAGS += -fPIC
+
+$(EXEC_TEST): CFLAGS += -DEXEC_TEST
+$(EXEC_TEST): exec.c env.c
+	$(CC) -o $@ $(CFLAGS) $^ -ldl
+
+$(ENV_TEST): CFLAGS += -DENV_TEST
+$(ENV_TEST): env.c
+	$(CC) -o $@ $(CFLAGS) $^
+
+run_tests: $(EXEC_TEST) $(ENV_TEST)
+	./$(ENV_TEST)
+	./$(EXEC_TEST)
 
 AppRun_patched.c: AppRun.c
 	patch -p1 --output $@  < AppRun.c.patch
@@ -23,3 +40,4 @@ AppRun_patched.c: AppRun.c
 AppRun.c:
 	wget -c "https://raw.githubusercontent.com/AppImage/AppImageKit/appimagetool/master/src/AppRun.c"
 
+.PHONY: checkrt test run_tests all clean