add export demo and test

_demo/go/export/use/Makefile

@@ -0,0 +1,84 @@
+# Makefile for C demo using Go exported library
+# Use LINK_TYPE environment variable to choose library type:
+# LINK_TYPE=static  - Link with static library (default)
+# LINK_TYPE=shared  - Link with shared library
+
+CC = clang
+CFLAGS = -Wall -Wextra -std=c99
+INCLUDES = -I..
+TARGET = main.out
+SOURCES = main.c
+HEADER = ../libexport.h
+
+# Default to static linking
+LINK_TYPE ?= static
+
+# Platform detection
+UNAME_S := $(shell uname -s)
+ifeq ($(UNAME_S),Darwin)
+    SHARED_EXT = dylib
+    PLATFORM_LIBS =
+else
+    SHARED_EXT = so
+    PLATFORM_LIBS = $(shell pkg-config --libs libunwind 2>/dev/null || echo -lunwind)
+endif
+
+# Library and flags based on link type
+ifeq ($(LINK_TYPE),shared)
+    BUILDMODE = c-shared
+    LIBRARY = ../libexport.$(SHARED_EXT)
+    LDFLAGS = -L.. -lexport -lpthread -lm $(shell pkg-config --libs bdw-gc || echo -lgc) $(PLATFORM_LIBS)
+    BUILD_MSG = "Building Go shared library..."
+    LINK_MSG = "Linking with shared library..."
+else
+    BUILDMODE = c-archive
+    LIBRARY = ../libexport.a
+    LDFLAGS = $(LIBRARY) -lpthread -lm $(shell pkg-config --libs bdw-gc || echo -lgc) $(PLATFORM_LIBS)
+    BUILD_MSG = "Building Go static library..."
+    LINK_MSG = "Linking with static library..."
+endif
+
+.PHONY: all clean run build-go
+
+all: build-go $(TARGET)
+
+# Build the Go library first
+build-go:
+	@echo $(BUILD_MSG)
+	cd .. && ../../../llgo.sh build -buildmode $(BUILDMODE) -o export .
+
+# Build the C executable
+$(TARGET): $(SOURCES) $(LIBRARY) $(HEADER)
+	@echo $(LINK_MSG)
+	$(CC) $(CFLAGS) $(INCLUDES) -o $(TARGET) $(SOURCES) $(LDFLAGS)
+
+# Run the executable
+run: $(TARGET)
+	@echo "Running C demo..."
+ifeq ($(LINK_TYPE),shared)
+	@echo "Setting library path for shared library..."
+	LD_LIBRARY_PATH=.. DYLD_LIBRARY_PATH=.. ./$(TARGET)
+else
+	./$(TARGET)
+endif
+
+# Clean build artifacts
+clean:
+	rm -f $(TARGET)
+	rm -f ../libexport.a ../libexport.h ../libexport.so ../libexport.dylib
+
+# Help target
+help:
+	@echo "Available targets:"
+	@echo "  all       - Build Go library and C executable"
+	@echo "  build-go  - Build only the Go library"
+	@echo "  run       - Build and run the C demo"
+	@echo "  clean     - Clean all build artifacts"
+	@echo "  help      - Show this help message"
+	@echo ""
+	@echo "Environment variables:"
+	@echo "  LINK_TYPE - Library type: 'static' (default) or 'shared'"
+	@echo ""
+	@echo "Examples:"
+	@echo "  make run                    # Use static library"
+	@echo "  LINK_TYPE=shared make run   # Use shared library"