Created Makefile + extra.mk and updated .c files against warnings

gnumake/custom/Makefile

@@ -0,0 +1,40 @@
+# Compiler and flags
+CC := gcc
+CFLAGS := -Wall -Wextra -g
+
+# Conditional block (debug vs release)
+ifeq ($(DEBUG),1)
+CFLAGS += -DDEBUG
+else
+CFLAGS += -O2
+endif
+
+# Targets
+TARGETS := greeting parts
+
+# Function to get executable name
+make_exec = $(basename $(notdir $(1)))
+
+# Default rule
+all: $(TARGETS)
+
+# Include extra rules
+include extra.mk
+
+# Build greeting executable from greeting.c
+greeting: greeting.c
+	@echo "Compiling greeting.c..."
+	$(CC) $(CFLAGS) -o $(call make_exec,$<) $<
+
+# Build parts executable using part1.c, part2.c and header.h
+parts: part1.c part2.c header.h
+	@echo "Compiling parts (part1 + part2)..."
+	$(CC) $(CFLAGS) -o parts part1.c part2.c
+
+# Clean rule
+clean:
+	@echo "Cleaning executables..."
+	rm -f greeting parts
+
+# Phony rules
+.PHONY: all clean help

gnumake/custom/extra.mk

@@ -0,0 +1,9 @@
+# Extra Makefile with additional rule
+
+help:
+	@echo "Available commands:"
+	@echo "  make           - build all targets"
+	@echo "  make greeting  - build greeting program"
+	@echo "  make parts     - build parts program"
+	@echo "  make clean     - remove executables"
+	@echo "  make DEBUG=1   - build with debug flags"