First pass at ESQLITE_USE_SYSTEM

This allows the system SQLite to be used instead of the included
file

Author: michaelkschmidt

Makefile

@@ -2,19 +2,39 @@ ifeq ($(ERL_EI_INCLUDE_DIR),)
 $(error ERL_EI_INCLUDE_DIR not set. Invoke via mix)
 endif
 
+ifeq ($(ERL_EI_LIBDIR),)
+$(error ERL_EI_LIBDIR not set. Invoke via mix)
+endif
+
+
 # Set Erlang-specific compile and linker flags
 ERL_CFLAGS ?= -I$(ERL_EI_INCLUDE_DIR)
-ERL_LDFLAGS ?= -L$(ERL_EI_LIBDIR)
+ERL_LDFLAGS ?= -L$(ERL_EI_LIBDIR) -lei
 
-SRC=$(wildcard c_src/*.c)
-OBJ=$(SRC:.c=.o)
+SRC = $(wildcard c_src/*.c)
 
 LDFLAGS ?= -fPIC -shared -pedantic
+
 CFLAGS ?= -fPIC -O2
 SQLITE_CFLAGS = -DSQLITE_THREADSAFE=1 -DSQLITE_USE_URI -DSQLITE_ENABLE_FTS3 \
 -DSQLITE_ENABLE_FTS3_PARENTHESIS -DSQLITE_ENABLE_FTS5 -DSQLITE_ENABLE_JSON1 \
 -DSQLITE_ENABLE_RTREE
 
+# ESQLITE_USE_SYSTEM - Use the system sqlite3 library
+#   Set this ENV var to compile/link against the system sqlite3 library.
+#   This is necessary if other applications are accessing the same sqlite db
+#   as the versions must match exactly
+
+ifdef ESQLITE_USE_SYSTEM
+	CFLAGS += -fPIC
+	LDFLAGS += -fPIC -shared -pedantic -lsqlite3
+else
+	SRC += $(wildcard c_src/sqlite3/*.c)
+	CFLAGS += $(SQLITE_CFLAGS) -fPIC -Ic_src/sqlite3
+endif
+
+OBJ = $(SRC:.c=.o)
+
 NIF=priv/esqlite3_nif.so
 
 all: priv $(NIF)
@@ -23,7 +43,7 @@ priv:
 	mkdir -p priv
 
 %.o: %.c
-	$(CC) -c $(ERL_CFLAGS) $(CFLAGS) $(SQLITE_CFLAGS) -o $@ $<
+	$(CC) -c $(ERL_CFLAGS) $(CFLAGS) -o $@ $<
 
 $(NIF): $(OBJ)
 	$(CC) $^ $(ERL_LDFLAGS) $(LDFLAGS) -o $@

c_src/sqlite3.c renamed to c_src/sqlite3/sqlite3.c

@@ -88,6 +88,10 @@ defmodule Esqlite3Nif do
   def enable_load_extension(_db, _ref, _dest), do: :erlang.nif_error(:nif_library_not_loaded)
 
   @on_load :load_nif
+  # Don't load the file automatically during compile
+  # If we are cross compiled this will cause an error
+  @compile {:autoload, false}
+
   @doc false
   def load_nif do
     require Logger