Changed GetOptions to use sequence

Commit 582200a made `ReusableStringStream`'s index reservation thread safe, however it's still accessing the `m_streams` vector outside the lock. This makes it so that the `add` call returns the pointer in addition to the index so that the lock doesn't need to get acquired again until destruction.

The issue with accessing `m_streams` outside the lock is that `add` can call `push_back` on the vector, which might re-allocate. If this re-allocation occurs concurrently with anther thread trying to index into this array, you get UB (typically a null pointer read).

.clang-tidy

@@ -78,5 +78,5 @@ WarningsAsErrors: >-
   readability-duplicate-include,
 HeaderFilterRegex: '.*\.(c|cxx|cpp)$'
 FormatStyle:     none
-CheckOptions: {}
+CheckOptions: []
 ...

src/catch2/catch_registry_hub.cpp

@@ -96,6 +96,7 @@ namespace Catch {
     }
     void cleanUp() {
         cleanupSingletons();
+        cleanUpContext();
     }
     std::string translateActiveException() {
         return getRegistryHub().getExceptionTranslatorRegistry().translateActiveException();

src/catch2/interfaces/catch_interfaces_capture.hpp

@@ -10,7 +10,6 @@
 
 #include <string>
 
-#include <catch2/internal/catch_context.hpp>
 #include <catch2/internal/catch_stringref.hpp>
 #include <catch2/internal/catch_result_type.hpp>
 #include <catch2/internal/catch_unique_ptr.hpp>
@@ -101,19 +100,7 @@ namespace Catch {
         virtual void exceptionEarlyReported() = 0;
     };
 
-    namespace Detail {
-        [[noreturn]]
-        void missingCaptureInstance();
-    }
-    inline IResultCapture& getResultCapture() {
-        if (auto* capture = getCurrentContext().getResultCapture()) {
-            return *capture;
-        } else {
-            Detail::missingCaptureInstance();
-        }
-
-
-    }
+    IResultCapture& getResultCapture();
 
 }
 

src/catch2/internal/catch_context.cpp

@@ -6,14 +6,25 @@
 
 // SPDX-License-Identifier: BSL-1.0
 #include <catch2/internal/catch_context.hpp>
+#include <catch2/internal/catch_noncopyable.hpp>
 #include <catch2/internal/catch_random_number_generator.hpp>
 
 namespace Catch {
 
-    Context Context::currentContext;
+    Context* Context::currentContext = nullptr;
+
+    void cleanUpContext() {
+        delete Context::currentContext;
+        Context::currentContext = nullptr;
+    }
+    void Context::createContext() {
+        currentContext = new Context();
+    }
 
     Context& getCurrentMutableContext() {
-        return Context::currentContext;
+        if ( !Context::currentContext ) { Context::createContext(); }
+        // NOLINTNEXTLINE(clang-analyzer-core.uninitialized.UndefReturn)
+        return *Context::currentContext;
     }
 
     SimplePcg32& sharedRng() {

src/catch2/internal/catch_context.hpp

@@ -19,9 +19,11 @@ namespace Catch {
         IConfig const* m_config = nullptr;
         IResultCapture* m_resultCapture = nullptr;
 
-        CATCH_EXPORT static Context currentContext;
+        CATCH_EXPORT static Context* currentContext;
         friend Context& getCurrentMutableContext();
         friend Context const& getCurrentContext();
+        static void createContext();
+        friend void cleanUpContext();
 
     public:
         constexpr IResultCapture* getResultCapture() const {
@@ -38,9 +40,15 @@ namespace Catch {
     Context& getCurrentMutableContext();
 
     inline Context const& getCurrentContext() {
-        return Context::currentContext;
+        // We duplicate the logic from `getCurrentMutableContext` here,
+        // to avoid paying the call overhead in debug mode.
+        if ( !Context::currentContext ) { Context::createContext(); }
+        // NOLINTNEXTLINE(clang-analyzer-core.uninitialized.UndefReturn)
+        return *Context::currentContext;
     }
 
+    void cleanUpContext();
+
     class SimplePcg32;
     SimplePcg32& sharedRng();
 }

src/catch2/internal/catch_reusable_string_stream.cpp

@@ -12,6 +12,7 @@
 
 #include <cstdio>
 #include <sstream>
+#include <tuple>
 #include <vector>
 
 namespace Catch {
@@ -23,16 +24,16 @@ namespace Catch {
         std::ostringstream m_referenceStream; // Used for copy state/ flags from
         Detail::Mutex m_mutex;
 
-        auto add() -> std::size_t {
+        auto add() -> std::pair<std::size_t, std::ostringstream*> {
             Detail::LockGuard _( m_mutex );
             if( m_unused.empty() ) {
                 m_streams.push_back( Detail::make_unique<std::ostringstream>() );
-                return m_streams.size()-1;
+                return { m_streams.size()-1, m_streams.back().get() };
             }
             else {
                 auto index = m_unused.back();
                 m_unused.pop_back();
-                return index;
+                return { index, m_streams[index].get() };
             }
         }
 
@@ -46,10 +47,10 @@ namespace Catch {
         }
     };
 
-    ReusableStringStream::ReusableStringStream()
-    :   m_index( Singleton<StringStreams>::getMutable().add() ),
-        m_oss( Singleton<StringStreams>::getMutable().m_streams[m_index].get() )
-    {}
+    ReusableStringStream::ReusableStringStream() {
+        std::tie( m_index, m_oss ) =
+            Singleton<StringStreams>::getMutable().add();
+    }
 
     ReusableStringStream::~ReusableStringStream() {
         static_cast<std::ostringstream*>( m_oss )->str("");

src/catch2/internal/catch_run_context.cpp

@@ -21,7 +21,6 @@
 #include <catch2/internal/catch_assertion_handler.hpp>
 #include <catch2/internal/catch_test_failure_exception.hpp>
 #include <catch2/internal/catch_result_type.hpp>
-#include <catch2/interfaces/catch_interfaces_capture.hpp>
 
 #include <cassert>
 #include <algorithm>
@@ -810,6 +809,13 @@ namespace Catch {
         }
     }
 
+    IResultCapture& getResultCapture() {
+        if (auto* capture = getCurrentContext().getResultCapture())
+            return *capture;
+        else
+            CATCH_INTERNAL_ERROR("No result capture instance");
+    }
+
     void IResultCapture::pushScopedMessage( MessageInfo&& message ) {
         Detail::g_messages.push_back( CATCH_MOVE( message ) );
     }
@@ -840,10 +846,4 @@ namespace Catch {
         return getCurrentContext().getConfig()->rngSeed();
     }
 
-
-    namespace Detail {
-        void missingCaptureInstance() {
-            CATCH_INTERNAL_ERROR( "No result capture instance" );
-        }
-    } // namespace Detail
 }