bitcoin/psbt: psbt_txid needs a tal ctx.

It returns a wally_tx; it's an anti-pattern not to hand in a tal context.

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

bitcoin/psbt.c

@@ -706,7 +706,8 @@ struct wally_psbt *fromwire_wally_psbt(const tal_t *ctx,
 }
 
 /* This only works on a non-final psbt because we're ALL SEGWIT! */
-void psbt_txid(const struct wally_psbt *psbt, struct bitcoin_txid *txid,
+void psbt_txid(const tal_t *ctx,
+	       const struct wally_psbt *psbt, struct bitcoin_txid *txid,
 	       struct wally_tx **wtx)
 {
 	struct wally_tx *tx;
@@ -732,7 +733,7 @@ void psbt_txid(const struct wally_psbt *psbt, struct bitcoin_txid *txid,
 
 	wally_txid(tx, txid);
 	if (wtx)
-		*wtx = tx;
+		*wtx = tal_steal(ctx, tx);
 	else
 		wally_tx_free(tx);
 }

bitcoin/psbt.h

@@ -62,11 +62,13 @@ bool psbt_is_finalized(const struct wally_psbt *psbt);
 
 /**
  * psbt_txid - get the txid of the psbt (what it would be after finalization)
+ * @ctx: the context to allocate wtx off, if *@wtx isn't NULL.
  * @psbt: the psbt.
  * @txid: the transaction id (output)
  * @wtx: if non-NULL, returns a copy of the transaction (caller must wally_tx_free).
  */
-void psbt_txid(const struct wally_psbt *psbt, struct bitcoin_txid *txid,
+void psbt_txid(const tal_t *ctx,
+	       const struct wally_psbt *psbt, struct bitcoin_txid *txid,
 	       struct wally_tx **wtx);
 
 /* psbt_elements_normalize_fees - Figure out the fee output for a PSET

openingd/dualopend.c

@@ -1036,8 +1036,7 @@ static u8 *accepter_start(struct state *state, const u8 *oc2_msg)
 		return NULL;
 
 	/* Find the funding transaction txid */
-	struct wally_tx *funding_tx;
-	psbt_txid(psbt, &state->funding_txid, &funding_tx);
+	psbt_txid(NULL, psbt, &state->funding_txid, NULL);
 
 	wscript = bitcoin_redeem_2of2(state,
 				      &state->our_funding_pubkey,

plugins/spender/multifundchannel.c

@@ -1392,7 +1392,7 @@ perform_funding_tx_finalize(struct multifundchannel_command *mfc)
 
 	/* Generate the TXID.  */
 	mfc->txid = tal(mfc, struct bitcoin_txid);
-	psbt_txid(mfc->psbt, mfc->txid, NULL);
+	psbt_txid(NULL, mfc->psbt, mfc->txid, NULL);
 
 	plugin_log(mfc->cmd->plugin, LOG_DBG,
 		   "mfc %"PRIu64": funding tx %s: %s",

plugins/txprepare.c

@@ -150,7 +150,7 @@ static struct command_result *signpsbt_done(struct command *cmd,
 	tal_free(utx->tx);
 
 	/* The txid from the final should match our expectation. */
-	psbt_txid(utx->psbt, &txid, &utx->tx);
+	psbt_txid(utx, utx->psbt, &txid, &utx->tx);
 	if (!bitcoin_txid_eq(&txid, &utx->txid)) {
 		return command_fail(cmd, LIGHTNINGD,
 				    "Signed tx changed txid? Had '%s' now '%s'",
@@ -197,7 +197,7 @@ static struct command_result *finish_txprepare(struct command *cmd,
 
 	utx = tal(NULL, struct unreleased_tx);
 	utx->psbt = tal_steal(utx, txp->psbt);
-	psbt_txid(txp->psbt, &utx->txid, &utx->tx);
+	psbt_txid(utx, txp->psbt, &utx->txid, &utx->tx);
 
 	/* If this is a withdraw, we sign and send immediately. */
 	if (txp->is_withdraw) {