common: add tal_gather_wally() function to reparent libwally objs.

This lets us reduce leaks, and ease their detection.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

common/setup.c

@@ -5,8 +5,6 @@
 #include <sodium.h>
 #include <wally_core.h>
 
-static const tal_t *wally_tal_ctx;
-
 static void *wally_tal(size_t size)
 {
 	return tal_arr_label(wally_tal_ctx, u8, size, "wally_notleak");

common/utils.c

@@ -5,6 +5,7 @@
 #include <ccan/tal/str/str.h>
 #include <locale.h>
 
+const tal_t *wally_tal_ctx;
 secp256k1_context *secp256k1_ctx;
 const tal_t *tmpctx;
 
@@ -15,6 +16,15 @@ bool is_elements(const struct chainparams *chainparams)
 	return chainparams->is_elements;
 }
 
+/* Steal any wally allocations onto this context. */
+void tal_gather_wally(const tal_t *ctx)
+{
+	tal_t *p;
+	assert(tal_first(wally_tal_ctx));
+	while ((p = tal_first(wally_tal_ctx)) != NULL)
+		tal_steal(ctx, p);
+}
+
 #if DEVELOPER
 /* If you've got a softref, we assume no reallocs. */
 static void dont_move_softref(tal_t *ctx, enum tal_notify_type ntype, void *info)

common/utils.h

@@ -84,6 +84,9 @@ void setup_tmpctx(void);
 /* Free any children of tmpctx. */
 void clean_tmpctx(void);
 
+/* Steal any wally allocations onto this context. */
+void tal_gather_wally(const tal_t *ctx);
+
 /* Define sha256_eq. */
 STRUCTEQ_DEF(sha256, 0, u);
 
@@ -106,4 +109,7 @@ STRUCTEQ_DEF(ripemd160, 0, u);
 #define IFDEV(dev, nondev) (nondev)
 #endif
 
+/* Context which all wally allocations use (see common/setup.c) */
+extern const tal_t *wally_tal_ctx;
+
 #endif /* LIGHTNING_COMMON_UTILS_H */