Merge #21613: build: enable -Wdocumentation

a4e970a build: enable -Wdocumentation if suppressing external warnings (fanquake)
3b0078f doc: fixup -Wdocumentation issues (fanquake)
c6edcf1 build: suppress libevent warnings if supressing external warnings (fanquake)

Pull request description:

  Enable `-Wdocumentation` by taking advantage of our `--enable-suppress-external-warnings` flag. Most of the CIs are using this flag now, so any regressions should be caught.

  This also required modifying libevents flags when suppressing warnings, as depending on the version being built against, that could generate a large number of warnings. i.e:
  ```bash
  In file included from httpserver.cpp:34:
  In file included from ./support/events.h:12:
  /usr/local/Cellar/libevent/2.1.12/include/event2/http.h:464:11: warning: parameter 'req' not found in the function declaration [-Wdocumentation]
     @param req a request object
            ^~~
  /usr/local/Cellar/libevent/2.1.12/include/event2/http.h:465:11: warning: parameter 'databuf' not found in the function declaration [-Wdocumentation]
     @param databuf the data chunk to send as part of the reply.
            ^~~~~~~
  /usr/local/Cellar/libevent/2.1.12/include/event2/http.h:467:11: warning: parameter 'call' not found in the function declaration [-Wdocumentation]
     @param call back's argument.
            ^~~~
  /usr/local/Cellar/libevent/2.1.12/include/event2/http.h:939:4: warning: declaration is marked with '@deprecated' command but does not have a deprecation attribute [-Wdocumentation-deprecated-sync]
    @deprecated  This function is deprecated; you probably want to use
    ~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  /usr/local/Cellar/libevent/2.1.12/include/event2/http.h:946:1: note: add a deprecation attribute to the declaration to silence this warning
  char *evhttp_decode_uri(const char *uri);
  ^
  __AVAILABILITY_INTERNAL_DEPRECATED
  /usr/local/Cellar/libevent/2.1.12/include/event2/http.h:979:5: warning: declaration is marked with '@deprecated' command but does not have a deprecation attribute [-Wdocumentation-deprecated-sync]
     @deprecated This function is deprecated as of Libevent 2.0.9.  Use
     ~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  /usr/local/Cellar/libevent/2.1.12/include/event2/http.h:987:1: note: add a deprecation attribute to the declaration to silence this warning
  int evhttp_parse_query(const char *uri, struct evkeyvalq *headers);
  ^
  __AVAILABILITY_INTERNAL_DEPRECATED
  /usr/local/Cellar/libevent/2.1.12/include/event2/http.h:1002:11: warning: parameter 'query_parse' not found in the function declaration [-Wdocumentation]
     @param query_parse the query portion of the URI
            ^~~~~~~~~~~
  /usr/local/Cellar/libevent/2.1.12/include/event2/http.h:1002:11: note: did you mean 'uri'?
     @param query_parse the query portion of the URI
            ^~~~~~~~~~~
            uri
  69 warnings generated.
  ```

  Note that a lot of these have already been fixed upstream.

ACKs for top commit:
  laanwj:
    Concept and code review ACK a4e970a
  practicalswift:
    cr ACK a4e970a: automatic compiler feedback comes sooner and is more reliable than manual reviewer feedback
  jonatack:
    Light ACK a4e970a skimmed the changes, clang 11 build is clean with the change, verified -Wdocumentation build warnings with this change when a doc fix was reverted

Tree-SHA512: 57a1e30cffcc8bcceee72d85f58ebe29eae525861c70acb237541bd480c51ede89875c033042c0af376fdbb49fb7f588ef9282a47c6e78f9d4501c41f1b21eb6

Author: fanquake

configure.ac

@@ -439,6 +439,10 @@ if test "x$enable_werror" = "xyes"; then
                         [AC_LANG_SOURCE([[struct A { virtual void f(); }; struct B : A { void f() final; };]])])
   AX_CHECK_COMPILE_FLAG([-Werror=unreachable-code-loop-increment],[ERROR_CXXFLAGS="$ERROR_CXXFLAGS -Werror=unreachable-code-loop-increment"],,[[$CXXFLAG_WERROR]])
   AX_CHECK_COMPILE_FLAG([-Werror=mismatched-tags], [ERROR_CXXFLAGS="$ERROR_CXXFLAGS -Werror=mismatched-tags"], [], [$CXXFLAG_WERROR])
+
+  if test x$suppress_external_warnings != xno ; then
+    AX_CHECK_COMPILE_FLAG([-Werror=documentation],[ERROR_CXXFLAGS="$ERROR_CXXFLAGS -Werror=documentation"],,[[$CXXFLAG_WERROR]])
+  fi
 fi
 
 if test "x$CXXFLAGS_overridden" = "xno"; then
@@ -466,6 +470,10 @@ if test "x$CXXFLAGS_overridden" = "xno"; then
                         [AC_LANG_SOURCE([[struct A { virtual void f(); }; struct B : A { void f() final; };]])])
   AX_CHECK_COMPILE_FLAG([-Wunreachable-code-loop-increment],[WARN_CXXFLAGS="$WARN_CXXFLAGS -Wunreachable-code-loop-increment"],,[[$CXXFLAG_WERROR]])
 
+  if test x$suppress_external_warnings != xno ; then
+    AX_CHECK_COMPILE_FLAG([-Wdocumentation],[WARN_CXXFLAGS="$WARN_CXXFLAGS -Wdocumentation"],,[[$CXXFLAG_WERROR]])
+  fi
+
   dnl Some compilers (gcc) ignore unknown -Wno-* options, but warn about all
   dnl unknown options if any other warning is produced. Test the -Wfoo case, and
   dnl set the -Wno-foo case if it works.
@@ -1485,6 +1493,10 @@ if test x$build_bitcoin_cli$build_bitcoind$bitcoin_enable_qt$use_tests$use_bench
   if test x$TARGET_OS != xwindows; then
     PKG_CHECK_MODULES([EVENT_PTHREADS], [libevent_pthreads >= 2.0.21],, [AC_MSG_ERROR([libevent_pthreads version 2.0.21 or greater not found.])])
   fi
+
+  if test x$suppress_external_warnings != xno; then
+    EVENT_CFLAGS=SUPPRESS_WARNINGS($EVENT_CFLAGS)
+  fi
 fi
 
 dnl QR Code encoding library check

src/net_processing.cpp

@@ -2062,7 +2062,7 @@ void PeerManagerImpl::ProcessHeadersMessage(CNode& pfrom, const Peer& peer,
 /**
  * Reconsider orphan transactions after a parent has been accepted to the mempool.
  *
- * @param[in/out]  orphan_work_set  The set of orphan transactions to reconsider. Generally only one
+ * @param[in,out]  orphan_work_set  The set of orphan transactions to reconsider. Generally only one
  *                                  orphan will be reconsidered on each call of this function. This set
  *                                  may be added to if accepting an orphan causes its children to be
  *                                  reconsidered.

src/netbase.h

@@ -172,7 +172,6 @@ CService LookupNumeric(const std::string& name, uint16_t portDefault = 0, DNSLoo
  * @param strSubnet A string representation of a subnet of the form `network
  *                address [ "/", ( CIDR-style suffix | netmask ) ]`(e.g.
  *                `2001:db8::/32`, `192.0.2.0/255.255.255.0`, or `8.8.8.8`).
- * @param ret The resulting internal representation of a subnet.
  *
  * @returns Whether the operation succeeded or not.
  */
@@ -235,7 +234,7 @@ void InterruptSocks5(bool interrupt);
  * @param port The destination port.
  * @param auth The credentials with which to authenticate with the specified
  *             SOCKS5 proxy.
- * @param sock The SOCKS5 proxy socket.
+ * @param socket The SOCKS5 proxy socket.
  *
  * @returns Whether or not the operation succeeded.
  *

src/policy/feerate.h

@@ -47,7 +47,6 @@ class CFeeRate
      *
      *  @param[in] nFeePaid  CAmount fee rate to construct with
      *  @param[in] nBytes    size_t bytes (units) to construct with
-     *  @returns   fee rate
      */
     CFeeRate(const CAmount& nFeePaid, size_t nBytes);
     /**

src/util/sock.h

@@ -161,7 +161,7 @@ class Sock
 
     /**
      * Check if still connected.
-     * @param[out] err The error string, if the socket has been disconnected.
+     * @param[out] errmsg The error string, if the socket has been disconnected.
      * @return true if connected
      */
     virtual bool IsConnected(std::string& errmsg) const;

src/validation.h

@@ -1029,7 +1029,7 @@ inline bool IsBlockPruned(const CBlockIndex* pblockindex)
 /**
  * Return the expected assumeutxo value for a given height, if one exists.
  *
- * @param height[in] Get the assumeutxo value for this height.
+ * @param[in] height Get the assumeutxo value for this height.
  *
  * @returns empty if no assumeutxo configuration exists for the given height.
  */

src/wallet/rpcwallet.cpp

@@ -1281,7 +1281,7 @@ static void MaybePushAddress(UniValue & entry, const CTxDestination &dest)
 /**
  * List transactions based on the given criteria.
  *
- * @param  pwallet        The wallet.
+ * @param  wallet         The wallet.
  * @param  wtx            The wallet transaction.
  * @param  nMinDepth      The minimum confirmation depth.
  * @param  fLong          Whether to include the JSON version of the transaction.

src/wallet/scriptpubkeyman.cpp

@@ -84,7 +84,7 @@ bool HaveKeys(const std::vector<valtype>& pubkeys, const LegacyScriptPubKeyMan&
 //! Recursively solve script and return spendable/watchonly/invalid status.
 //!
 //! @param keystore            legacy key and script store
-//! @param script              script to solve
+//! @param scriptPubKey        script to solve
 //! @param sigversion          script type (top-level / redeemscript / witnessscript)
 //! @param recurse_scripthash  whether to recurse into nested p2sh and p2wsh
 //!                            scripts or simply treat any script that has been