add shared target + improve error handling in lib

Makefile

@@ -1,23 +1,39 @@
-TARGET_LIB ?= libqments.a
+STATIC_LIB ?= libqments.a
+SHARED_LIB ?= libqments.so
 
 BD ?= build
 SRC_DIRS ?= src
 INCLUDE_DIRS ?= include
 
+SBD ?= $(BD)/shared
+
 SRC_FILES := $(shell find $(SRC_DIRS) -name *.c)
 OBJ_FILES := $(patsubst %.c,$(BD)/%.o,$(SRC_FILES))
 
-$(BD)/$(TARGET_LIB): $(OBJ_FILES)
+OBJ_FILES := $(patsubst %.c,$(BD)/%.o,$(SRC_FILES))
+SHARED_OBJ_FILES := $(patsubst %.c,$(SBD)/%.o,$(SRC_FILES))
+
+shared: $(SBD)/$(SHARED_LIB)
+static: $(BD)/$(STATIC_LIB)
+
+$(SBD)/$(SHARED_LIB): $(SHARED_OBJ_FILES)
+	$(CC) $(CFLAGS) -shared -o $@ -Wl,--whole-archive $^ -Wl,--no-whole-archive
+
+$(BD)/$(STATIC_LIB): $(OBJ_FILES)
 	mkdir -p $(@D)
 	ar rcs $@ $(OBJ_FILES)
 
+$(SBD)/%.o: %.c
+	mkdir -p $(@D)
+	$(CC) $(CFLAGS) -fPIC -c $< -o $@ -I $(INCLUDE_DIRS)
+
 $(BD)/%.o: %.c
 	mkdir -p $(@D)
 	$(CC) $(CFLAGS) -c $< -o $@ -I $(INCLUDE_DIRS)
 
-all: $(BD)/$(TARGET_LIB)
+all: shared static
 
 clean:
 	rm -rfI $(BD)/
 
-.PHONY: all clean
+.PHONY: all clean shared static