build: Drop bitcoin-tx and bitcoin-wallet dependencies on libevent

Bitcoin Core PR: bitcoin/bitcoin#18504

Pull request description:

  This fixes compile errors trying to build bitcoin-tx and bitcoin-wallet without libevent, which were reported by Luke Dashjr in bitcoin/bitcoin#18465

  The fix avoiding `bitcoin-tx` dependency on libevent just adds a conditional build rule. This is implemented in the first commit (more details in commit description).

  The fix avoiding `bitcoin-wallet` dependency on libevent requires minor code changes, because `bitcoin-wallet` (unlike `bitcoin-tx`) links against code that calls `urlDecode` / `evhttp_uridecode`. This fix is implemented in the second commit (again details in the commit description).

Author: PhotoshiNakamoto

build_msvc/libbitcoin_util/libbitcoin_util.vcxproj.in

@@ -8,6 +8,7 @@
     <ConfigurationType>StaticLibrary</ConfigurationType>
   </PropertyGroup>
   <ItemGroup>
+    <ClCompile Include="..\..\src\util\url.cpp" />
 @SOURCE_FILES@
   </ItemGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />

configure.ac

@@ -1265,7 +1265,7 @@ if test x$use_pkgconfig = xyes; then
         BITCOIN_QT_CHECK([PKG_CHECK_MODULES([QR], [libqrencode], [have_qrencode=yes], [have_qrencode=no])])
       fi
       if test x$build_bitcoin_cli$build_bitcoind$bitcoin_enable_qt$use_tests$use_bench != xnonononono; then
-        PKG_CHECK_MODULES([EVENT], [libevent >= 2.0.21],, [AC_MSG_ERROR(libevent version 2.0.21 or greater not found.)])
+        PKG_CHECK_MODULES([EVENT], [libevent], [use_libevent=yes], [AC_MSG_ERROR(libevent not found.)])
         if test x$TARGET_OS != xwindows; then
           PKG_CHECK_MODULES([EVENT_PTHREADS], [libevent_pthreads >= 2.0.21],, [AC_MSG_ERROR(libevent_pthreads version 2.0.21 or greater not found.)])
         fi
@@ -1285,7 +1285,7 @@ if test x$use_pkgconfig = xyes; then
 else
 
   if test x$build_bitcoin_cli$build_bitcoind$bitcoin_enable_qt$use_tests$use_bench != xnonononono; then
-    AC_CHECK_HEADER([event2/event.h],, AC_MSG_ERROR(libevent headers missing),)
+    AC_CHECK_HEADER([event2/event.h], [use_libevent=yes], AC_MSG_ERROR(libevent headers missing),)
     AC_CHECK_LIB([event],[main],EVENT_LIBS=-levent,AC_MSG_ERROR(libevent missing))
     if test x$TARGET_OS != xwindows; then
       AC_CHECK_LIB([event_pthreads],[main],EVENT_PTHREADS_LIBS=-levent_pthreads,AC_MSG_ERROR(libevent_pthreads missing))
@@ -1523,6 +1523,7 @@ AM_CONDITIONAL([ENABLE_QT_TESTS],[test x$BUILD_TEST_QT = xyes])
 AM_CONDITIONAL([ENABLE_BENCH],[test x$use_bench = xyes])
 AM_CONDITIONAL([USE_QRCODE], [test x$use_qr = xyes])
 AM_CONDITIONAL([USE_LCOV],[test x$use_lcov = xyes])
+AM_CONDITIONAL([USE_LIBEVENT],[test x$use_libevent = xyes])
 AM_CONDITIONAL([GLIBC_BACK_COMPAT],[test x$use_glibc_compat = xyes])
 AM_CONDITIONAL([HARDEN],[test x$use_hardening = xyes])
 AM_CONDITIONAL([ENABLE_SSE42],[test x$enable_sse42 = xyes])

src/Makefile.am

@@ -530,11 +530,14 @@ libbitcoin_util_a_SOURCES = \
   util/strencodings.cpp \
   util/string.cpp \
   util/time.cpp \
-  util/url.cpp \
 	util/matrixchecks.cpp \
 	util/matrixchecks.h \
   $(BITCOIN_CORE_H)
 
+if USE_LIBEVENT
+libbitcoin_util_a_SOURCES += util/url.cpp
+endif
+
 if GLIBC_BACK_COMPAT
 libbitcoin_util_a_SOURCES += compat/glibc_compat.cpp
 AM_LDFLAGS += $(COMPAT_LDFLAGS)

src/bitcoin-cli.cpp

@@ -15,6 +15,7 @@
 #include <util/strencodings.h>
 #include <util/system.h>
 #include <util/translation.h>
+#include <util/url.h>
 
 #include <functional>
 #include <memory>
@@ -29,6 +30,7 @@
 #include <compat/stdin.h>
 
 const std::function<std::string(const char*)> G_TRANSLATION_FUN = nullptr;
+UrlDecodeFn* const URL_DECODE = urlDecode;
 
 static const char DEFAULT_RPCCONNECT[] = "127.0.0.1";
 static const int DEFAULT_HTTP_CLIENT_TIMEOUT=900;

src/bitcoin-wallet.cpp

@@ -11,11 +11,13 @@
 #include <logging.h>
 #include <util/system.h>
 #include <util/translation.h>
+#include <util/url.h>
 #include <wallet/wallettool.h>
 
 #include <functional>
 
 const std::function<std::string(const char*)> G_TRANSLATION_FUN = nullptr;
+UrlDecodeFn* const URL_DECODE = nullptr;
 
 static void SetupWalletToolArgs()
 {

src/bitcoind.cpp

@@ -20,10 +20,12 @@
 #include <util/system.h>
 #include <util/threadnames.h>
 #include <util/translation.h>
+#include <util/url.h>
 
 #include <functional>
 
 const std::function<std::string(const char*)> G_TRANSLATION_FUN = nullptr;
+UrlDecodeFn* const URL_DECODE = urlDecode;
 
 static void WaitForShutdown(NodeContext& node)
 {

src/qt/main.cpp

@@ -5,6 +5,7 @@
 #include <qt/bitcoin.h>
 
 #include <util/translation.h>
+#include <util/url.h>
 
 #include <QCoreApplication>
 
@@ -15,5 +16,6 @@
 extern const std::function<std::string(const char*)> G_TRANSLATION_FUN = [](const char* psz) {
     return QCoreApplication::translate("bitcoin-core", psz).toStdString();
 };
+UrlDecodeFn* const URL_DECODE = urlDecode;
 
 int main(int argc, char* argv[]) { return GuiMain(argc, argv); }

src/test/util/setup_common.cpp

@@ -27,12 +27,14 @@
 #include <util/string.h>
 #include <util/time.h>
 #include <util/translation.h>
+#include <util/url.h>
 #include <validation.h>
 #include <validationinterface.h>
 
 #include <functional>
 
 const std::function<std::string(const char*)> G_TRANSLATION_FUN = nullptr;
+UrlDecodeFn* const URL_DECODE = nullptr;
 
 FastRandomContext g_insecure_rand_ctx;
 /** Random context to get unique temp data dirs. Separate from g_insecure_rand_ctx, which can be seeded from a const env var */

src/util/url.h

@@ -7,6 +7,8 @@
 
 #include <string>
 
-std::string urlDecode(const std::string &urlEncoded);
+using UrlDecodeFn = std::string(const std::string& url_encoded);
+UrlDecodeFn urlDecode;
+extern UrlDecodeFn* const URL_DECODE;
 
 #endif // BITCOIN_UTIL_URL_H

src/wallet/rpcwallet.cpp

@@ -78,9 +78,9 @@ bool HaveKey(const SigningProvider& wallet, const CKey& key)
 
 bool GetWalletNameFromJSONRPCRequest(const JSONRPCRequest& request, std::string& wallet_name)
 {
-    if (request.URI.substr(0, WALLET_ENDPOINT_BASE.size()) == WALLET_ENDPOINT_BASE) {
+    if (URL_DECODE && request.URI.substr(0, WALLET_ENDPOINT_BASE.size()) == WALLET_ENDPOINT_BASE) {
         // wallet endpoint was used
-        wallet_name = urlDecode(request.URI.substr(WALLET_ENDPOINT_BASE.size()));
+        wallet_name = URL_DECODE(request.URI.substr(WALLET_ENDPOINT_BASE.size()));
         return true;
     }
     return false;