Implemented #8931: Avoid hangs when process with embedded connection goes into stopped state.

Author: AlexPeshkoff

src/common/os/os_utils.h

@@ -386,6 +386,24 @@ namespace os_utils
 #endif
 	};
 
+	class StopHandler
+	{
+	public:
+#ifdef WIN_NT
+		explicit StopHandler(bool*)
+		{ }
+#else
+		explicit StopHandler(bool* stop);
+		explicit StopHandler(Firebird::MemoryPool&);
+		~StopHandler();
+
+	private:
+		static bool* stopPtr;
+
+		static void handler(void*);
+#endif
+	};
+
 } // namespace os_utils
 
 #endif // INCLUDE_OS_FILE_UTILS_H

src/common/os/posix/os_utils.cpp

@@ -451,4 +451,31 @@ void CtrlCHandler::handler(void*)
 	terminated = true;
 }
 
+/// class StopHandler
+
+bool* StopHandler::stopPtr = nullptr;
+
+StopHandler::StopHandler(bool* stop)
+{
+	fb_assert(!stopPtr);
+	stopPtr = stop;
+	ISC_signal(SIGTSTP, handler, 0);
+}
+
+StopHandler::StopHandler(MemoryPool&)
+{
+	ISC_signal(SIGTSTP, handler, 0);
+}
+
+StopHandler::~StopHandler()
+{
+	ISC_signal_cancel(SIGTSTP, handler, 0);
+}
+
+void StopHandler::handler(void*)
+{
+	if (stopPtr)
+		*stopPtr = true;
+}
+
 } // namespace os_utils

src/isql/isql.epp

@@ -301,6 +301,8 @@ static inline int fb_isdigit(const char c)
 typedef Array<char> CharBuffer;
 GlobalPtr<CharBuffer> charBuffer;
 
+static bool sigTstp = false;
+
 #ifdef WIN_NT
 
 GlobalPtr<Array<WCHAR>> wideBuffer;
@@ -789,6 +791,8 @@ int ISQL_main(int argc, char* argv[])
  *
  **************************************/
 
+	os_utils::StopHandler stopHandler(&sigTstp);
+
 #if defined(HAVE_EDITLINE_H) && defined(HAVE_LOCALE_H)
 	setlocale(LC_CTYPE, "");
 #endif
@@ -1023,7 +1027,22 @@ static void readNextInputLine(const char* prompt)
 		// CVC: On 2005-04-02, use an empty prompt when not working in
 		// interactive mode to behave like @@@ below at request by Pavel.
 		const char* new_prompt = Interactive ? prompt : "";
-		lastInputLine = readline(new_prompt);
+		for(;;)
+		{
+			lastInputLine = readline(new_prompt);
+
+			// In a case of ignored SIGTSTP (ctrl-Z typically) readline return NULL -
+			// same as for EOF case, causing normal termination. Let's avoid it.
+			if (!lastInputLine)
+			{
+				if (!sigTstp)
+					break;
+				sigTstp = false;
+				new_prompt = "";
+			}
+			else
+				break;
+		}
 
 		if (lastInputLine != NULL && strlen(lastInputLine) != 0) {
 			add_history(lastInputLine);

src/yvalve/why.cpp

@@ -48,6 +48,7 @@
 #include "../common/IntlParametersBlock.h"
 #include "../common/os/isc_i_proto.h"
 #include "../common/os/path_utils.h"
+#include "../common/os/os_utils.h"
 #include "../common/classes/alloc.h"
 #include "../common/classes/array.h"
 #include "../common/classes/stack.h"
@@ -863,6 +864,7 @@ class ShutdownInit
 	void signalInit()
 	{
 #ifdef UNIX
+		static GlobalPtr<os_utils::StopHandler> stopHandler;
 		static GlobalPtr<CtrlCHandler> ctrlCHandler;
 #else
 		static GlobalPtr<ShutdownInit> shutdownInit;