Phase 0.

Makefile

@@ -1,6 +1,7 @@
 CC ?= cc
 CXX ?= c++
 PKG_CONFIG ?= pkg-config
+FLTK_CONFIG ?= fltk-config
 BUILD_DIR ?= build
 PREFIX ?= /usr/local
 
@@ -13,10 +14,21 @@ LDFLAGS ?=
 CORE_SOURCES := src/core/xtlite.c src/graph/graph.c src/dsp/gain.c src/engine/offline_engine.c
 CORE_OBJECTS := $(CORE_SOURCES:%.c=$(BUILD_DIR)/%.o)
 TEST_OBJECT := $(BUILD_DIR)/tests/unit/test_core.o
-GUI_AVAILABLE := $(shell $(PKG_CONFIG) --exists fltk 2>/dev/null && echo yes)
+ifeq ($(shell $(PKG_CONFIG) --exists fltk 2>/dev/null && echo yes),yes)
+FLTK_CXXFLAGS := $(shell $(PKG_CONFIG) --cflags fltk)
+FLTK_LIBS := $(shell $(PKG_CONFIG) --libs fltk)
+GUI_AVAILABLE := yes
+else ifeq ($(shell $(FLTK_CONFIG) --version >/dev/null 2>&1 && echo yes),yes)
+FLTK_CXXFLAGS := $(shell $(FLTK_CONFIG) --cxxflags)
+FLTK_LIBS := $(shell $(FLTK_CONFIG) --ldflags)
+GUI_AVAILABLE := yes
+endif
 
-.PHONY: all clean test gui install
-all: $(BUILD_DIR)/libxtlite.a
+.PHONY: all clean test debug gui install
+all: $(BUILD_DIR)/libxtlite.a $(BUILD_DIR)/xtlite-check
+
+$(BUILD_DIR)/xtlite-check: $(BUILD_DIR)/src/main.o $(BUILD_DIR)/libxtlite.a
+	$(CC) $(LDFLAGS) -o $@ $^ -lm
 
 $(BUILD_DIR)/libxtlite.a: $(CORE_OBJECTS)
 	@mkdir -p $(@D)
@@ -24,30 +36,34 @@ $(BUILD_DIR)/libxtlite.a: $(CORE_OBJECTS)
 
 $(BUILD_DIR)/%.o: %.c
 	@mkdir -p $(@D)
-	$(CC) $(CFLAGS) -c $< -o $@
+	$(CC) $(CFLAGS) -MMD -MP -c $< -o $@
 
 $(BUILD_DIR)/%.o: %.cpp
 	@mkdir -p $(@D)
-	$(CXX) $(CXXFLAGS) $(shell $(PKG_CONFIG) --cflags fltk 2>/dev/null) -c $< -o $@
+	$(CXX) $(CXXFLAGS) $(FLTK_CXXFLAGS) -MMD -MP -c $< -o $@
 
 $(TEST_OBJECT): tests/unit/test_core.c
 	@mkdir -p $(@D)
-	$(CC) $(CFLAGS) -c $< -o $@
+	$(CC) $(CFLAGS) -MMD -MP -c $< -o $@
 
 $(BUILD_DIR)/test_core: $(TEST_OBJECT) $(BUILD_DIR)/libxtlite.a
 	$(CC) $(LDFLAGS) -o $@ $(TEST_OBJECT) $(BUILD_DIR)/libxtlite.a -lm
 
-test: $(BUILD_DIR)/test_core
+test: $(BUILD_DIR)/test_core $(BUILD_DIR)/xtlite-check
 	./$(BUILD_DIR)/test_core
+	./$(BUILD_DIR)/xtlite-check
+
+debug:
+	$(MAKE) BUILD_DIR="$(BUILD_DIR)/debug" CFLAGS="$(CFLAGS) -O0 -g3" CXXFLAGS="$(CXXFLAGS) -O0 -g3" all test
 
 ifeq ($(GUI_AVAILABLE),yes)
 gui: $(BUILD_DIR)/xtlite
 
 $(BUILD_DIR)/xtlite: $(BUILD_DIR)/src/gui/main.o $(BUILD_DIR)/src/gui/main_window.o $(BUILD_DIR)/libxtlite.a
-	$(CXX) $(LDFLAGS) -o $@ $^ $(shell $(PKG_CONFIG) --libs fltk) -lm
+	$(CXX) $(LDFLAGS) -o $@ $^ $(FLTK_LIBS) -lm
 else
 gui:
-	@echo "FLTK was not found by pkg-config. Install FLTK development files to build the GUI."
+	@echo "FLTK was not found by pkg-config or fltk-config. GUI requires FLTK development files."
 	@exit 1
 endif
 
@@ -58,3 +74,6 @@ install: all
 
 clean:
 	rm -rf "$(BUILD_DIR)"
+
+-include $(CORE_OBJECTS:.o=.d) $(TEST_OBJECT:.o=.d) $(BUILD_DIR)/src/main.d \
+    $(BUILD_DIR)/src/gui/main.d $(BUILD_DIR)/src/gui/main_window.d

README.md

@@ -1,4 +1,4 @@
-# xtlite — a lightweight, modular DAW
+# xtc — a lightweight, modular DAW
 
 `xtlite` is a new, energyXT-inspired digital audio workstation project. It is not a clone and contains no energyXT source code or assets.
 
@@ -31,6 +31,10 @@ make
 make test
 ```
 
+`make` also builds `build/xtlite-check`, a headless core startup/shutdown
+check. Use `make debug` for a separate debug build and test run. See
+[docs/BUILD.md](docs/BUILD.md) for the inspected toolchain and baseline limits.
+
 Build the optional FLTK GUI if FLTK is installed:
 
 ```sh

docs/BUILD.md

@@ -0,0 +1,57 @@
+# Build baseline
+
+Phase 0 retains the existing layout: public C headers in `include/xtlite`,
+C implementation modules under `src`, optional C++ GUI under `src/gui`, and
+tests under `tests`. `src/main.c` is a minimal headless startup/shutdown check;
+it does not initialize audio devices or open a GUI.
+
+## Commands
+
+```sh
+make clean all test
+./build/xtlite-check
+make debug
+make gui
+```
+
+`all` builds the static C library and startup check. `test` runs the existing
+core test and startup check. `debug` builds and tests separately in
+`build/debug`. `gui` builds the existing placeholder shell; it does not produce
+audio. Generated files remain under `build` and header changes trigger rebuilds.
+Compiler, flags, `BUILD_DIR`, `PKG_CONFIG`, `FLTK_CONFIG`, and installation
+`PREFIX` can be overridden through Make variables. C uses C99; GUI uses C++17.
+
+## Inspected Linux toolchain (2026-10-26)
+
+| Component | Available version | Role |
+| --- | --- | --- |
+| GCC / G++ | 16.2.1 | C core and optional C++ GUI |
+| GNU Make | 4.4.1 | Build and test driver |
+| pkg-config | 3.0.10 | Development package discovery |
+| FLTK | 1.4.5 | Optional GUI; discovered through `fltk-config` |
+| JACK | 3.1609.0 (pkg-config) | Candidate backend; not linked yet |
+| ALSA | 1.2.16.1 (pkg-config) | Future MIDI candidate; not linked yet |
+| Clang | 23.1.3 | Alternative compiler / diagnostics |
+
+Valgrind is also available. The core tests use a small in-tree C test harness
+and require no external test framework. FLTK has no `fltk.pc` on this host;
+the Makefile tries pkg-config first, then `fltk-config`.
+
+## Dependencies and licensing
+
+No new dependencies are introduced. The core needs the C runtime and math
+library. The repository is MIT licensed. The optional GUI uses maintained
+FLTK 1.4 (LGPL with FLTK's static-linking exception); its platform link flags
+come from the installed package. Distribution still requires review of all
+linked dependencies and notices. JACK and ALSA remain candidates only; backend
+selection and license review belong to Phase 2. No packages or system settings
+are changed by these build commands.
+
+## Next milestone
+
+Phase 1 must replace insertion-order gain processing with a validated,
+topologically scheduled offline plan, preallocated buffers, oscillator, gain,
+meter and output nodes, and deterministic routing tests. The current gain
+prototype is not a real-time engine. Public project persistence declarations
+also remain unimplemented. Hardware playback and interactive GUI behavior are
+outside this baseline.

docs/ROADMAP.md

@@ -4,6 +4,10 @@
 Inspect repository/toolchain, verify Makefile and minimal executable, document
 dependencies. No system changes without permission.
 
+Baseline implementation: headless startup/shutdown executable, core tests,
+separate debug build, optional FLTK shell build, and header dependencies.
+See [BUILD.md](BUILD.md) for toolchain, commands, licensing and limitations.
+
 ## Phase 1 — C core and offline processing
 Graph data structures, validation, cycle detection, topological ordering,
 preallocated buffers, test oscillator, gain and offline render tests.

src/main.c

@@ -0,0 +1,24 @@
+#include "xtlite/xtlite.h"
+#include "xtlite/xtlite_version.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+
+int main(void)
+{
+    xt_app *app = NULL;
+    xt_result result = xt_app_create(&app);
+
+    if (result != XT_OK) {
+        (void)fprintf(stderr, "Application initialization failed: %s\n",
+                      xt_result_string(result));
+        return EXIT_FAILURE;
+    }
+
+    xt_app_destroy(app);
+    if (printf("%s %s: core startup/shutdown OK\n",
+               XTLITE_PROJECT_NAME, XTLITE_VERSION_STRING) < 0) {
+        return EXIT_FAILURE;
+    }
+    return EXIT_SUCCESS;
+}