Merge bitcoin/bitcoin#22137: util: Properly handle -noincludeconf on command line (take 2)

fa910b47656d0e69cccb1f31804f2b11aa45d053 util: Properly handle -noincludeconf on command line (MarcoFalke)

Pull request description:

  Before:

  ```
  $ ./src/qt/bitcoin-qt -noincludeconf
  (memory violation, can be observed with valgrind or similar)
  ```

  After:

  ```
  $ ./src/qt/bitcoin-qt -noincludeconf
  (passes startup)
  ```

  Fixes https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=34884

ACKs for top commit:
  practicalswift:
    cr ACK fa910b47656d0e69cccb1f31804f2b11aa45d053: patch looks correct
  ryanofsky:
    Code review ACK fa910b47656d0e69cccb1f31804f2b11aa45d053. Nice cleanups!

Tree-SHA512: 5dfad82a78bca7a9a6bcc6aead2d7fbde166a09a5300a82f80dd1aee1de00e070bcb30b7472741a5396073b370898696e78c33038f94849219281d99358248ed

2 files changed, 26 insertions, 4 deletions

diff --git a/src/test/util_tests.cpp b/src/test/util_tests.cpp
index d463bcdd8e..7ce38519cf 100644
--- a/src/test/util_tests.cpp
+++ b/src/test/util_tests.cpp
@@ -329,6 +329,25 @@ BOOST_FIXTURE_TEST_CASE(util_CheckValue, CheckValueTest)
     CheckValue(M::ALLOW_ANY, "-value=abc", Expect{"abc"}.String("abc").Int(0).Bool(false).List({"abc"}));
 }
 
+struct NoIncludeConfTest {
+    std::string Parse(const char* arg)
+    {
+        TestArgsManager test;
+        test.SetupArgs({{"-includeconf", ArgsManager::ALLOW_ANY}});
+        std::array argv{"ignored", arg};
+        std::string error;
+        (void)test.ParseParameters(argv.size(), argv.data(), error);
+        return error;
+    }
+};
+
+BOOST_FIXTURE_TEST_CASE(util_NoIncludeConf, NoIncludeConfTest)
+{
+    BOOST_CHECK_EQUAL(Parse("-noincludeconf"), "");
+    BOOST_CHECK_EQUAL(Parse("-includeconf"), "-includeconf cannot be used from commandline; -includeconf=\"\"");
+    BOOST_CHECK_EQUAL(Parse("-includeconf=file"), "-includeconf cannot be used from commandline; -includeconf=\"file\"");
+}
+
 BOOST_AUTO_TEST_CASE(util_ParseParameters)
 {
     TestArgsManager testArgs;
diff --git a/src/util/system.cpp b/src/util/system.cpp
index 5b87806a45..13ccf7463e 100644
--- a/src/util/system.cpp
+++ b/src/util/system.cpp
@@ -365,11 +365,14 @@ bool ArgsManager::ParseParameters(int argc, const char* const argv[], std::strin
         m_settings.command_line_options[key].push_back(value);
     }
 
-    // we do not allow -includeconf from command line
+    // we do not allow -includeconf from command line, only -noincludeconf
     if (auto* includes = util::FindKey(m_settings.command_line_options, "includeconf")) {
-        const auto& include{*util::SettingsSpan(*includes).begin()}; // pick first value as example
-        error = "-includeconf cannot be used from commandline; -includeconf=" + include.write();
-        return false;
+        const util::SettingsSpan values{*includes};
+        // Range may be empty if -noincludeconf was passed
+        if (!values.empty()) {
+            error = "-includeconf cannot be used from commandline; -includeconf=" + values.begin()->write();
+            return false; // pick first value as example
+        }
     }
     return true;
 }