Fix disengage failure logs for FatalConditionHandlerGuard

FatalConditionHandlerGuard is used within RunContext::invokeActiveTestCase().
The intent of this guard is to avoid binary crash without failed test being
reported.
Still in case FatalConditionHandlerGuard destructor being called during stack
unwinding AND finds unexpected top-level filter for SEH unhandled exception,
the binary may still crash. As result of such crash the original exception
details are being hidden.

As the Catch2 provides only `CATCH_CATCH_ANON` macro, with no access to
exception details by design, looks like the best way to handle issue is to:
 - state requirements explicitly by `noexcept` specifier
 - use `Catch::cerr()` to print out possible issue notification

Signed-off-by: Kochetkov, Yuriy <yuriyx.kochetkov@intel.com>

src/catch2/internal/catch_fatal_condition_handler.cpp

@@ -40,7 +40,7 @@ namespace Catch {
     // If neither SEH nor signal handling is required, the handler impls
     // do not have to do anything, and can be empty.
     void FatalConditionHandler::engage_platform() {}
-    void FatalConditionHandler::disengage_platform() {}
+    void FatalConditionHandler::disengage_platform() noexcept {}
     FatalConditionHandler::FatalConditionHandler() = default;
     FatalConditionHandler::~FatalConditionHandler() = default;
 
@@ -124,9 +124,11 @@ namespace Catch {
         previousTopLevelExceptionFilter = SetUnhandledExceptionFilter(topLevelExceptionFilter);
     }
 
-    void FatalConditionHandler::disengage_platform() {
+    void FatalConditionHandler::disengage_platform() noexcept {
         if (SetUnhandledExceptionFilter(previousTopLevelExceptionFilter) != topLevelExceptionFilter) {
-            CATCH_RUNTIME_ERROR("Could not restore previous top level exception filter");
+            Catch::cerr()
+                << "Unexpected SEH unhandled exception filter on disengage."
+                << " The filter was restored, but might be rolled back unexpectedly.";
         }
         previousTopLevelExceptionFilter = nullptr;
     }
@@ -168,7 +170,7 @@ namespace Catch {
     static stack_t oldSigStack{};
     static struct sigaction oldSigActions[sizeof(signalDefs) / sizeof(SignalDefs)]{};
 
-    static void restorePreviousSignalHandlers() {
+    static void restorePreviousSignalHandlers() noexcept {
         // We set signal handlers back to the previous ones. Hopefully
         // nobody overwrote them in the meantime, and doesn't expect
         // their signal handlers to live past ours given that they
@@ -231,7 +233,7 @@ namespace Catch {
 #endif
 
 
-    void FatalConditionHandler::disengage_platform() {
+    void FatalConditionHandler::disengage_platform() noexcept {
         restorePreviousSignalHandlers();
     }
 

src/catch2/internal/catch_fatal_condition_handler.hpp

@@ -32,7 +32,7 @@ namespace Catch {
         // Should be if-defed to work on current platform, can assume
         // engage-disengage 1:1 pairing.
         void engage_platform();
-        void disengage_platform();
+        void disengage_platform() noexcept;
     public:
         // Should also have platform-specific implementations as needed
         FatalConditionHandler();
@@ -44,7 +44,7 @@ namespace Catch {
             engage_platform();
         }
 
-        void disengage() {
+        void disengage() noexcept {
             assert(m_started && "Handler cannot be uninstalled without being installed first");
             m_started = false;
             disengage_platform();