From 90f95391b3e8340e4eca779c85c244312eb979ba Mon Sep 17 00:00:00 2001
From: Alexander Patel <acpatel@andrew.cmu.edu>
Date: Thu, 17 Jun 2021 00:47:33 -0700
Subject: [PATCH] Makefile: compile objects individually, then link

This commit updates the Makefile to complile each .c source file into
an object before linking. The benefit of this is that only the necessary
files will be recompiled when modifying the code.

We also move the Makefile and build.bat up to the root directory of the
repo. This is so that calling make directly builds the binaries.
Both files are updated to adapt to the new directory structure.

With this change, initial build times are increased from ~3s to ~10s on
my machine. However, subsequent build times are improved.

As a result of this change, SConstruct is somewhat deprecated. We can
update this as well if necessary in a future change.

I verified that the build completes successfully and tests pass for
both ubuntu and windows 10.

A future change could compile src/ files into a static library to be
linked with cli/, if necessary.

Issue: #64
---
 .github/workflows/build.yml    |  7 ++--
 .gitignore                     |  3 +-
 Makefile                       | 59 ++++++++++++++++++++++++++++++++++
 build/SConstruct => SConstruct |  0
 build/build.bat => build.bat   |  4 +--
 build/.gitignore               |  5 ---
 build/Makefile                 | 22 -------------
 7 files changed, 65 insertions(+), 35 deletions(-)
 create mode 100644 Makefile
 rename build/SConstruct => SConstruct (100%)
 rename build/build.bat => build.bat (98%)
 delete mode 100644 build/.gitignore
 delete mode 100644 build/Makefile

diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 9b6cb1c..400701c 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -19,8 +19,7 @@ jobs:
       - uses: actions/checkout@v2
       - name: Run the Makefile.
         run: |
-          cd build
-          make
+          make all
       - name: Run tests.
         run: |
           python3 tests/tests.py
@@ -32,7 +31,6 @@ jobs:
       - uses: actions/checkout@v2      
       - name: Run build batch script.
         run: |
-          cd build
           cmd /c build.bat
       - name: Run tests.
         run: |
@@ -45,8 +43,7 @@ jobs:
       - uses: actions/checkout@v2
       - name: Run the Makefile.
         run: |
-          cd build
-          make
+          make all
       - name: Run tests.
         run: |
           python3 tests/tests.py
diff --git a/.gitignore b/.gitignore
index 7ab78ce..1fcc62b 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,8 +2,9 @@
 # PocketLang ignore list
 .vs/
 .vscode/
+build/
 
-# It's a convinent batch scrpit to run pyton script
+# It's a convinent batch script to run pyton script
 # changing directory and run another script.
 # Which are compile wasm and generate pages.
 docs/build.bat
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..05ee0f4
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,59 @@
+
+# ##  Copyright (c) 2020-2021 Thakee Nathees
+# ##  Distributed Under The MIT License
+
+CC             = gcc
+CFLAGS         = -fPIC -Wno-int-to-pointer-cast
+DEBUG_CFLAGS   = -D DEBUG -g3 -Og
+RELEASE_CFLAGS = -g -O3
+LDFLAGS        = -lm
+
+TARGET_EXEC = pocket
+BUILD_DIR   = ./build
+
+SRC_DIRS = ./src ./cli
+INC_DIRS = ./src/include
+
+SRCS := $(shell find $(SRC_DIRS) -maxdepth 1 -name *.c)
+OBJS := $(SRCS:.c=.o)
+DEPS := $(OBJS:.o=.d)
+
+INC_FLAGS := $(addprefix -I,$(INC_DIRS))
+DEP_FLAGS  = -MMD -MP
+CC_FLAGS   = $(INC_FLAGS) $(DEP_FLAGS) $(CFLAGS)
+
+DEBUG_DIR     = $(BUILD_DIR)/debug
+DEBUG_TARGET  = $(DEBUG_DIR)/$(TARGET_EXEC)
+DEBUG_OBJS   := $(addprefix $(DEBUG_DIR)/, $(OBJS))
+
+RELEASE_DIR     = $(BUILD_DIR)/release
+RELEASE_TARGET  = $(RELEASE_DIR)/$(TARGET_EXEC)
+RELEASE_OBJS   := $(addprefix $(RELEASE_DIR)/, $(OBJS))
+
+.PHONY: debug release all clean
+
+# default; target if run as `make`
+debug: $(DEBUG_TARGET)
+
+$(DEBUG_TARGET): $(DEBUG_OBJS)
+	$(CC) $^ -o $@ $(LDFLAGS)
+
+$(DEBUG_DIR)/%.o: %.c
+	@mkdir -p $(dir $@)
+	$(CC) $(CC_FLAGS) $(DEBUG_CFLAGS) -c $< -o $@
+
+release: $(RELEASE_TARGET)
+
+$(RELEASE_TARGET): $(RELEASE_OBJS)
+	$(CC) $^ -o $@ $(LDFLAGS)
+
+$(RELEASE_DIR)/%.o: %.c
+	@mkdir -p $(dir $@)
+	$(CC) $(CC_FLAGS) $(RELEASE_CFLAGS) -c $< -o $@
+
+all: debug release
+
+clean:
+	rm -rf $(BUILD_DIR)
+
+-include $(DEPS)
diff --git a/build/SConstruct b/SConstruct
similarity index 100%
rename from build/SConstruct
rename to SConstruct
diff --git a/build/build.bat b/build.bat
similarity index 98%
rename from build/build.bat
rename to build.bat
index 2027891..a81529c 100644
--- a/build/build.bat
+++ b/build.bat
@@ -95,11 +95,11 @@ set root_dir=..\..\..\
 
 if "%debug_build%"=="false" (
 	set cflags=%cflags% -O2 -MD
-	set target_dir=release\
+	set target_dir=build\release\
 ) else (
 	set cflags=%cflags% -MDd -ZI
 	set addnl_cdefines=%addnl_cdefines% /DDEBUG
-	set target_dir=debug\
+	set target_dir=build\debug\
 )
 
 if "%shared_lib%"=="true" (
diff --git a/build/.gitignore b/build/.gitignore
deleted file mode 100644
index 00f78a2..0000000
--- a/build/.gitignore
+++ /dev/null
@@ -1,5 +0,0 @@
-*
-!.gitignore
-!SConstruct
-!build.bat
-!Makefile
diff --git a/build/Makefile b/build/Makefile
deleted file mode 100644
index 4de14f2..0000000
--- a/build/Makefile
+++ /dev/null
@@ -1,22 +0,0 @@
-
-##  Copyright (c) 2020-2021 Thakee Nathees
-##  Distributed Under The MIT License
-
-CC          = gcc
-CFLAGS      = -lm -fPIC -Wno-int-to-pointer-cast
-INCLUDE_DIR = -I../src/include
-SOURCES     = ../cli/*.c ../src/*.c
-
-all: debug
-
-debug:
-	@mkdir -p debug/
-	$(CC) -o debug/pocket $(SOURCES) $(INCLUDE_DIR) $(CFLAGS) -D DEBUG -g3 -Og
-
-release:
-	@mkdir -p release/
-	$(CC) -o release/pocket $(SOURCES) $(INCLUDE_DIR) $(CFLAGS) -g -O3
-
-clean:
-	rm -rf debug/
-	rm -rf release/