Improve shared library build and installation

- Add configurable install paths via INSTALL_PREFIX, INSTALL_LIB_DIR,
  INSTALL_INCLUDE_DIR, and INSTALL_BIN_DIR variables
- Add EXT_CFLAGS to capture user-provided CFLAGS and CPPFLAGS
- Hide internal symbols with -fvisibility=hidden, exposing only the
  public API (sqlite3_vec_init, sqlite3_vec_numpy_init,
  sqlite3_vec_static_blobs_init)
- Remove sudo from install target (users run sudo make install if needed)

Inspired by asg017#149

Co-Authored-By: Harry-Chen <cjc-2008@hotmail.com>
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: 3 people

Makefile

@@ -3,9 +3,10 @@ COMMIT=$(shell git rev-parse HEAD)
 VERSION=$(shell cat VERSION)
 DATE=$(shell date +'%FT%TZ%z')
 
-INSTALL_LIB_DIR = /usr/local/lib
-INSTALL_INCLUDE_DIR = /usr/local/include
-INSTALL_BIN_DIR = /usr/local/bin
+INSTALL_PREFIX ?= /usr/local
+INSTALL_LIB_DIR ?= $(INSTALL_PREFIX)/lib
+INSTALL_INCLUDE_DIR ?= $(INSTALL_PREFIX)/include
+INSTALL_BIN_DIR ?= $(INSTALL_PREFIX)/bin
 
 ifndef CC
 CC=gcc
@@ -14,6 +15,9 @@ ifndef AR
 AR=ar
 endif
 
+# Capture user-provided flags
+EXT_CFLAGS := $(CFLAGS) $(CPPFLAGS)
+
 ifeq ($(shell uname -s),Darwin)
 CONFIG_DARWIN=y
 else ifeq ($(OS),Windows_NT)
@@ -98,15 +102,16 @@ $(BUILD_DIR): $(prefix)
 $(TARGET_LOADABLE): sqlite-vec.c sqlite-vec.h $(prefix)
 	$(CC) \
 		-fPIC -shared \
+		-fvisibility=hidden \
 		-Wall -Wextra \
 		-Ivendor/ \
 		-O3 \
-		$(CFLAGS) \
+		$(CFLAGS) $(EXT_CFLAGS) \
 		$< -o $@ \
 		$(LDLIBS)
 
 $(TARGET_STATIC): sqlite-vec.c sqlite-vec.h $(prefix) $(OBJS_DIR)
-	$(CC) -Ivendor/ $(CFLAGS) -DSQLITE_CORE -DSQLITE_VEC_STATIC \
+	$(CC) -Ivendor/ -fvisibility=hidden $(CFLAGS) $(EXT_CFLAGS) -DSQLITE_CORE -DSQLITE_VEC_STATIC \
 	-O3 -c  $< -o $(OBJS_DIR)/vec.o
 	$(AR) rcs $@ $(OBJS_DIR)/vec.o
 
@@ -134,21 +139,22 @@ $(LIBS_DIR)/shell.a: $(OBJS_DIR)/shell.o $(LIBS_DIR)
 	$(AR) rcs $@ $<
 
 $(OBJS_DIR)/sqlite-vec.o: sqlite-vec.c $(OBJS_DIR)
-	$(CC) -c -g3 -Ivendor/ -I./ $(CFLAGS) $< -o $@
+	$(CC) -c -g3 -fvisibility=hidden -Ivendor/ -I./ $(CFLAGS) $(EXT_CFLAGS) $< -o $@
 
 $(LIBS_DIR)/sqlite-vec.a: $(OBJS_DIR)/sqlite-vec.o $(LIBS_DIR)
 	$(AR) rcs $@ $<
 
 
 $(TARGET_CLI): sqlite-vec.h $(LIBS_DIR)/sqlite-vec.a $(LIBS_DIR)/shell.a $(LIBS_DIR)/sqlite3.a examples/sqlite3-cli/core_init.c $(prefix)
 	$(CC) -g3  \
+	-fvisibility=hidden \
 	-Ivendor/ -I./ \
 	-DSQLITE_CORE \
 	-DSQLITE_VEC_STATIC \
 	-DSQLITE_THREADSAFE=0 -DSQLITE_ENABLE_FTS4 \
 	-DSQLITE_ENABLE_STMT_SCANSTATUS -DSQLITE_ENABLE_BYTECODE_VTAB -DSQLITE_ENABLE_EXPLAIN_COMMENTS \
 	-DSQLITE_EXTRA_INIT=core_init \
-	$(CFLAGS) \
+	$(CFLAGS) $(EXT_CFLAGS) \
 	-ldl -lm \
 	examples/sqlite3-cli/core_init.c $(LIBS_DIR)/shell.a $(LIBS_DIR)/sqlite3.a $(LIBS_DIR)/sqlite-vec.a -o $@
 
@@ -224,7 +230,7 @@ install:
 		install -m 644 $(TARGET_STATIC) $(INSTALL_LIB_DIR); \
 	fi
 	@if [ -f $(TARGET_CLI) ]; then \
-		sudo install -m 755 $(TARGET_CLI) $(INSTALL_BIN_DIR); \
+		install -m 755 $(TARGET_CLI) $(INSTALL_BIN_DIR); \
 	fi
 	ldconfig
 

sqlite-vec.h.tmpl

@@ -8,12 +8,12 @@
 #endif
 
 #ifdef SQLITE_VEC_STATIC
-  #define SQLITE_VEC_API
+  #define SQLITE_VEC_API __attribute__((visibility("default")))
 #else
   #ifdef _WIN32
     #define SQLITE_VEC_API __declspec(dllexport)
   #else
-    #define SQLITE_VEC_API
+    #define SQLITE_VEC_API __attribute__((visibility("default")))
   #endif
 #endif