src/db.c: WIP: integrate SQLite3 with talloc allocator

The current version of this commit enables a custom memory
allocator for SQLite3 via SQLITE_CONFIG_MALLOC. If OsmoHLR is
compiled with ENABLE_TALLOC macro, talloc is used. Otherwise
the default malloc/realloc/free are used.

There are lots of debug messages for each call. They are helpful
for comparison heap usage footprints between both talloc & malloc.

NOTE: SQLite3 version 3.8.2 fails (at least) to init the database
with talloc, and there is some big difference in heap usage
footprint compared to malloc. At the same time, with the recent
SQLite3 version 3.24.0, both heap usage footprints are identical,
and OsmoHLR works fine...

Change-Id: Icfe67ed0f063b63e6794f9516da3003d01cf20a7

src/db.c

@@ -18,10 +18,12 @@
  */
 
 #include <osmocom/core/utils.h>
+#include <osmocom/core/talloc.h>
 
 #include <stdbool.h>
 #include <sqlite3.h>
 #include <string.h>
+#include <malloc.h>
 
 #include "logging.h"
 #include "db.h"
@@ -72,6 +74,109 @@ static const char *stmt_sql[] = {
 	[DB_STMT_AUC_3G_DELETE] = "DELETE FROM auc_3g WHERE subscriber_id = $subscriber_id",
 };
 
+/* Dedicated talloc context for SQLite */
+static void *db_sqlite_ctx = NULL;
+/* TEMP: used for memory footprint debugging */
+static int ctr = 0;
+
+/* talloc or malloc? */
+// #define ENABLE_TALLOC
+
+static void *tall_xMalloc(int size)
+{
+#ifdef ENABLE_TALLOC
+	void *p = talloc_size(db_sqlite_ctx, size);
+	int s = talloc_total_size(p);
+#else
+	void *p = malloc(size);
+	int s = malloc_usable_size(p);
+#endif
+	/* TEMP: used for memory footprint debugging */
+	printf("[%d] %s size_req=%d vs size_act=%d ptr=%c\n",
+		ctr++, __func__, size, s, p != NULL ? '+' : '!');
+	return p;
+}
+
+static void tall_xFree(void *ptr)
+{
+#ifdef ENABLE_TALLOC
+	int s = talloc_total_size(ptr);
+	talloc_free(ptr);
+#else
+	int s = malloc_usable_size(ptr);
+	free(ptr);
+#endif
+	/* TEMP: used for memory footprint debugging */
+	printf("[%d] %s size=%d\n", ctr++, __func__, s);
+}
+
+static void *tall_xRealloc(void *ptr, int size)
+{
+#ifdef ENABLE_TALLOC
+	void *p = talloc_realloc_fn(db_sqlite_ctx, ptr, size);
+	int s = talloc_total_size(p);
+#else
+	void *p = realloc(ptr, size);
+	int s = malloc_usable_size(p);
+#endif
+	/* TEMP: used for memory footprint debugging */
+	printf("[%d] %s size_req=%d vs size_act=%d ptr=%c\n",
+		ctr++, __func__, size, s, p != NULL ? '+' : '!');
+	return p;
+}
+
+static int tall_xSize(void *ptr)
+{
+#ifdef ENABLE_TALLOC
+	int s = talloc_total_size(ptr);
+#else
+	int s = malloc_usable_size(ptr);
+#endif
+	/* TEMP: used for memory footprint debugging */
+	printf("[%d] %s size=%d\n", ctr++, __func__, s);
+	return s;
+}
+
+static int tall_xRoundup(int size)
+{
+	/**
+	 * DUMMY: return size 'as-is'...
+	 * AFAIK talloc doesn't round up the allocation size.
+	 */
+	return size;
+}
+
+static int tall_xInit(void *data)
+{
+	/* DUMMY: nothing to initialize */
+	return 0;
+}
+
+static void tall_xShutdown(void *data)
+{
+	/* DUMMY: nothing to deinitialize */
+}
+
+/* Interface between SQLite and talloc memory allocator */
+static const struct sqlite3_mem_methods tall_sqlite_if = {
+	/* Memory allocation function */
+	.xMalloc = &tall_xMalloc,
+	/* Free a prior allocation */
+	.xFree = &tall_xFree,
+	/* Resize an allocation */
+	.xRealloc = &tall_xRealloc,
+	/* Return the size of an allocation */
+	.xSize = &tall_xSize,
+	/* Round up request size to allocation size */
+	.xRoundup = &tall_xRoundup,
+	/* Initialize the memory allocator */
+	.xInit = &tall_xInit,
+	/* Deinitialize the memory allocator */
+	.xShutdown = &tall_xShutdown,
+	/* Argument to xInit() and xShutdown() */
+	.pAppData = NULL,
+};
+
 static void sql3_error_log_cb(void *arg, int err_code, const char *msg)
 {
 	LOGP(DDB, LOGL_ERROR, "(%d) %s\n", err_code, msg);
@@ -231,6 +336,15 @@ struct db_context *db_open(void *ctx, const char *fname, bool enable_sqlite_logg
 	LOGP(DDB, LOGL_INFO, "Compiled against SQLite3 lib version %s\n", SQLITE_VERSION);
 	LOGP(DDB, LOGL_INFO, "Running with SQLite3 lib version %s\n", sqlite3_libversion());
 
+	db_sqlite_ctx = talloc_named_const(dbc, 0, "SQLite3");
+
+	/* Configure SQLite3 to use talloc memory allocator */
+	rc = sqlite3_config(SQLITE_CONFIG_MALLOC, &tall_sqlite_if);
+	if (rc != SQLITE_OK) {
+		LOGP(DDB, LOGL_ERROR, "Unable to configure SQLite3 "
+			"to use talloc, using default memory allocator\n");
+	}
+
 	dbc->fname = talloc_strdup(dbc, fname);
 
 	for (i = 0; i < 0xfffff; i++) {