Demo static lib

libadd/add.c

@@ -0,0 +1 @@
+int add(int a, int b) { return a + b; }

libadd/include/add.h

@@ -0,0 +1,6 @@
+#ifndef ADD_H
+#define ADD_H
+
+int add(int a, int b);
+
+#endif // ADD_H

libadd/makefile

@@ -0,0 +1,34 @@
+# Makefile for the add library
+# Builds a static library from the add.c file
+
+# Library name
+LIB = libadd.a
+
+# Compiler
+CC = gcc
+
+# Compiler flags
+CFLAGS = -Wall -Werror -Wextra -pedantic
+CFLAGS += -std=c99 -O3
+
+# Source file
+SRC = add.c
+
+# Object file
+OBJ = $(SRC:.c=.o)
+
+# Build the library
+$(LIB): $(OBJ)
+	ar rcs $(LIB) $(OBJ)
+
+# Build the object file
+$(OBJ): $(SRC)
+	$(CC) $(CFLAGS) -c $(SRC)
+
+format:
+	clang-format -i *.c include/*.h
+
+# Clean the object files
+clean:
+	rm -f $(OBJ)
+	rm -f $(LIB)

makefile

@@ -1,4 +1,4 @@
-# Compiler and assembler
+#dd Compiler and assembler
 CC = 		gcc
 AS = 		as
 LD = 		ld
@@ -20,6 +20,7 @@ CFLAGS += -Wno-unused-local-typedefs
 CFLAGS += -Wno-unused-const-variable
 CFLAGS += -Wno-unused-macros
 CFLAGS += -O3
+CFLAGS += -Ilibadd/include
 CFLAGS += -g
 
 GITHASH = $(shell git rev-parse --short HEAD)
@@ -36,6 +37,9 @@ OBJS := $(patsubst src/%.c,build/%.o,$(SRCS))
 
 all: $(TARGET)
 
+libadd/libadd.a:
+	$(MAKE) -C libadd
+
 # For convenience
 run: $(TARGET)
 	@./$(TARGET)
@@ -45,7 +49,7 @@ mkbuilddir:
 	@mkdir -p build
 
 # Link the object files into the target binary
-$(TARGET): $(OBJS)
+$(TARGET): $(OBJS) libadd/libadd.a
 	@$(CC) $(CFLAGS) -o $@ $^
 	@echo -e "LD \t$^"
 
@@ -67,6 +71,7 @@ clean:
 	rm -r build
 	rm -f build/*.o
 	rm -f $(TARGET)*
+	$(MAKE) -C libadd clean --no-print-directory
 
 # Create a signed release
 tar: $(TARGET_TAR)

src/main.c

@@ -1,6 +1,8 @@
+#include <add.h>
 #include <stdio.h>
 
 int main(int argc, const char **argv) {
   printf("Hello, World!\n");
+  printf("add(1, 2) = %d\n", add(1, 2));
   return 0;
 }