short_channel_id: catch parsing errors.

I upgraded my node with --disable-compat, and a heap of channels closed like:

	CHANNELD_NORMAL:We disagree on short_channel_ids: I have 557653x0x1351, you say 557653x2373x1", 

This is because the scids are strings in the databases, and it failed to parse
them properly.

Now we'll not start if that happens.

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

bitcoin/short_channel_id.h

@@ -50,13 +50,13 @@ static inline u16 short_channel_id_outnum(const struct short_channel_id *scid)
 void mk_short_channel_id(struct short_channel_id *scid,
 			 u32 blocknum, u32 txnum, u16 outnum);
 
-bool short_channel_id_from_str(const char *str, size_t strlen,
-			       struct short_channel_id *dst);
+bool WARN_UNUSED_RESULT short_channel_id_from_str(const char *str, size_t strlen,
+						  struct short_channel_id *dst);
 
 char *short_channel_id_to_str(const tal_t *ctx, const struct short_channel_id *scid);
 
-bool short_channel_id_dir_from_str(const char *str, size_t strlen,
-				   struct short_channel_id_dir *scidd);
+bool WARN_UNUSED_RESULT short_channel_id_dir_from_str(const char *str, size_t strlen,
+						      struct short_channel_id_dir *scidd);
 
 char *short_channel_id_dir_to_str(const tal_t *ctx,
 				  const struct short_channel_id_dir *scidd);

wallet/db.h

@@ -134,8 +134,8 @@ void *sqlite3_column_arr_(const tal_t *ctx, sqlite3_stmt *stmt, int col,
 
 bool sqlite3_bind_short_channel_id(sqlite3_stmt *stmt, int col,
 				   const struct short_channel_id *id);
-bool sqlite3_column_short_channel_id(sqlite3_stmt *stmt, int col,
-				     struct short_channel_id *dest);
+WARN_UNUSED_RESULT bool sqlite3_column_short_channel_id(sqlite3_stmt *stmt, int col,
+							struct short_channel_id *dest);
 bool sqlite3_bind_short_channel_id_array(sqlite3_stmt *stmt, int col,
 					 const struct short_channel_id *id);
 struct short_channel_id *

wallet/wallet.c

@@ -594,7 +594,8 @@ static struct channel *wallet_stmt2channel(const tal_t *ctx, struct wallet *w, s
 
 	if (sqlite3_column_type(stmt, 2) != SQLITE_NULL) {
 		scid = tal(tmpctx, struct short_channel_id);
-		sqlite3_column_short_channel_id(stmt, 2, scid);
+		if (!sqlite3_column_short_channel_id(stmt, 2, scid))
+			return NULL;
 	} else {
 		scid = NULL;
 	}