Replace build scripts with a Makefile

Single Makefile supports native builds (pkg-config) and cross-compilation
(CROSS_COMPILE/PREFIX env vars). Fixes -Wformat-truncation and
-Wstringop-truncation warnings at -O2 by sizing current_file to match
audio_files (256) and replacing strncpy with snprintf.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

CLAUDE.md

@@ -10,17 +10,23 @@ See `docs/sdlamp2-fsd.md` for the full functional specification and changelog.
 
 ## Build and Run
 
-**Dependencies:** SDL2, SDL2_image, FFmpeg libraries (libavformat, libavcodec, libavutil, libswresample). Installed via system package manager; resolved at build time with `sdl2-config` and `pkgconf`.
+**Dependencies:** SDL2, SDL2_image, FFmpeg libraries (libavformat, libavcodec, libavutil, libswresample). Installed via system package manager (native) or into the Buildroot sysroot (cross-compile).
 
 ```sh
-./build.sh              # macOS — builds to build/sdlamp2
-./build_aarch64.sh      # Linux aarch64 variant
+make                    # native build — uses pkg-config
+make clean              # remove build artifacts
 ./build/sdlamp2 [audio_directory]
 ```
 
+Cross-compilation inside the Docker toolchain container (where `CROSS_COMPILE` and `PREFIX` are set by the environment):
+
+```sh
+make                    # picks up CROSS_COMPILE and PREFIX automatically
+```
+
 The controls spritesheet (`controls.png`) is embedded in the binary. If an external `controls.png` exists in the current working directory it takes precedence, allowing custom skins. Audio directory defaults to cwd if not specified.
 
-No test suite, no linter, no Makefile/CMake.
+No test suite, no linter.
 
 ## Architecture
 

Makefile

@@ -0,0 +1,32 @@
+CC = $(CROSS_COMPILE)gcc
+
+CFLAGS  = -Wall -Wno-unused -O2
+LDLIBS  = -lSDL2 -lSDL2_image -lavformat -lavcodec -lavutil -lswresample
+
+ifdef PREFIX
+  # Cross-compile: headers and libraries live under PREFIX
+  CFLAGS += -I$(PREFIX)/include -I$(PREFIX)/include/SDL2
+  LDLIBS := -L$(PREFIX)/lib $(LDLIBS)
+else
+  # Native: use pkg-config
+  PKG_CONFIG ?= pkg-config
+  PKGS = sdl2 SDL2_image libavformat libavcodec libavutil libswresample
+  CFLAGS += $(shell $(PKG_CONFIG) --cflags $(PKGS))
+  LDLIBS  = $(shell $(PKG_CONFIG) --libs $(PKGS))
+endif
+
+BUILD_DIR = build
+TARGET    = $(BUILD_DIR)/sdlamp2
+
+.PHONY: all clean
+
+all: $(TARGET)
+
+$(TARGET): src/sdlamp2.c src/controls_png.h | $(BUILD_DIR)
+	$(CC) $(CFLAGS) -o $@ $< $(LDLIBS)
+
+$(BUILD_DIR):
+	mkdir -p $@
+
+clean:
+	rm -f $(TARGET)

build.sh

@@ -1,15 +0,0 @@
-#!/bin/sh
-
-pushd build 2>&1 >/dev/null
-
-gcc -Wall -Wno-unused -O0 -ggdb3 \
-  -o sdlamp2 \
-  `sdl2-config --cflags --libs` \
-  `pkgconf --cflags --libs libavformat` \
-  `pkgconf --cflags --libs libavcodec` \
-  `pkgconf --cflags --libs libavutil` \
-  `pkgconf --cflags --libs libswresample` \
-  -lSDL2_image \
-  ../src/sdlamp2.c
-
-popd 2>&1 >/dev/null

build_aarch64.sh

@@ -1,15 +0,0 @@
-#!/bin/bash
-
-pushd build 2>&1 >/dev/null
-
-gcc -Wall -Wno-unused \
-  -o sdlamp2 \
-  `sdl2-config --cflags --libs` \
-  -I/usr/include/aarch64-linux-gnu -L/usr/lib/aarch64-linux-gnu -lavformat \
-  -I/usr/include/aarch64-linux-gnu -L/usr/lib/aarch64-linux-gnu -lavcodec \
-  -I/usr/include/aarch64-linux-gnu -L/usr/lib/aarch64-linux-gnu -lavutil \
-  -I/usr/include/aarch64-linux-gnu -L/usr/lib/aarch64-linux-gnu -lswresample \
-  -lSDL2_image \
-  ../src/sdlamp2.c
-
-popd 2>&1 >/dev/null

docs/sdlamp2-fsd.md

@@ -30,7 +30,7 @@ This document specifies the functional requirements for an SDL2 based media play
 ## 4. Design principles
 
 - Version control (git) must be used
-- Compilation should be performed by a simple shell script or batch file, not a complicated build system like make or cmake
+- Compilation should be performed by a simple Makefile supporting both native and cross-compilation
 - C source code files should be formatted using "Google" style with an additional change of `ColumnLimit` set to 100
 - Less is more, minimize dependencies, avoid pulling in extra libraries, always talk through with owner first
 - Keep it simple, apply Casey Muratori's `semantic compression` principles, don't refactor too soon or write code that's too clever for its own good
@@ -43,6 +43,10 @@ This document specifies the functional requirements for an SDL2 based media play
 
 ## 6. Changelog
 
+### 2026-02-13 — Replace build scripts with Makefile
+
+- **Makefile**: Replaced `build.sh` (macOS) and `build_aarch64.sh` (Linux ARM) with a single `Makefile`. Native builds use `pkg-config` to resolve SDL2 and FFmpeg flags; cross-compilation uses `CROSS_COMPILE` and `PREFIX` environment variables set by the Docker/Buildroot toolchain.
+
 ### 2026-02-13 — Raw joystick fallback for non-standard controllers
 
 - **Joystick fallback**: When no SDL GameController mapping exists for a connected device, the joystick is now opened directly via `SDL_JoystickOpen()` as a fallback. This fixes d-pad and face button input on devices like the Anbernic retro handheld whose GUID is not in SDL's GameController database.

src/sdlamp2.c

@@ -49,7 +49,7 @@ static SDL_bool paused = SDL_TRUE;
 static Decoder decoder = {0};
 
 static char audio_dir[512] = ".";
-static char current_file[512] = "";
+static char current_file[256] = "";
 static char audio_files[MAX_FILES][256];
 static int num_audio_files = 0;
 static int current_file_index = 0;
@@ -111,8 +111,7 @@ static void save_position(const char* filename, double seconds) {
           snprintf(lines[num_lines], sizeof(lines[0]), "%s\t%.2f", filename, seconds);
           found = SDL_TRUE;
         } else {
-          strncpy(lines[num_lines], line, sizeof(lines[0]) - 1);
-          lines[num_lines][sizeof(lines[0]) - 1] = '\0';
+          snprintf(lines[num_lines], sizeof(lines[0]), "%s", line);
         }
         num_lines++;
       }
@@ -210,8 +209,7 @@ static void scan_audio_files(const char* dir) {
   while ((entry = readdir(d)) != NULL && num_audio_files < MAX_FILES) {
     if (entry->d_name[0] == '.') continue;
     if (has_audio_extension(entry->d_name)) {
-      strncpy(audio_files[num_audio_files], entry->d_name, 255);
-      audio_files[num_audio_files][255] = '\0';
+      snprintf(audio_files[num_audio_files], sizeof(audio_files[0]), "%s", entry->d_name);
       num_audio_files++;
     }
   }