Remove pointer cast in CRPCTable::dumpArgMap

CRPCTable::dumpArgMap currently works by casting RPC command unique_id
integer field to a function pointer, and then calling the function. The
unique_id field wasn't supposed to be used this way (it's meant to be
used to detect RPC aliases), and this code segfaults in the rpc_help.py
test in multiprocess PR https://github.com/bitcoin/bitcoin/pull/10102
because wallet RPC functions aren't directly accessible from the node
process.

Fix this by adding a new GET_ARGS request mode to retrieve argument
information similar to the way the GET_HELP mode retrieves help
information.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/rpc/util.h b/src/rpc/util.h
index aaca887900..90521949a6 100644
--- a/src/rpc/util.h
+++ b/src/rpc/util.h
@@ -337,8 +337,8 @@ public:
 
     UniValue HandleRequest(const JSONRPCRequest& request);
     std::string ToString() const;
-    /** Append the named args that need to be converted from string to another JSON type */
-    void AppendArgMap(UniValue& arr) const;
+    /** Return the named args that need to be converted from string to another JSON type */
+    UniValue GetArgMap() const;
     /** If the supplied number of args is neither too small nor too high */
     bool IsValidNumArgs(size_t num_args) const;
     std::vector<std::string> GetArgNames() const;