libposix: deep refactor; add sys/posixly command

With these changes, libposix (and newlib) can run MirBSD Korn Shell.

qa/lib/newlib/214-sigsetjmp.c

@@ -0,0 +1,132 @@
+#include <signal.h>
+#include <setjmp.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+sigset_t sigset;
+sigjmp_buf mark;
+int catcherWasCalled;
+
+void catcher(int);
+void p(void);
+
+int main(int argc, char *argv[]) {
+
+	int result = 0;
+	int returnCode = 0;
+
+	/*
+	 * Block the SIGUSR2 signal.  This signal set will be
+	 * saved as part of the environment by the sigsetjmp()
+	 * function and subsequently restored by the siglongjmp()
+	 * function.
+	 */
+
+	sigemptyset(&sigset);
+	sigaddset(&sigset, SIGUSR2);
+	sigprocmask(SIG_SETMASK, &sigset, NULL);
+
+	/* Save the stack environment and the current signal mask */
+
+	returnCode = sigsetjmp(mark, 1);
+
+	/* Handle the sigsetjmp return code */
+
+	switch(returnCode) {
+	case  0:
+		printf("sigsetjmp() has been called\n");
+
+		/*
+		 * Call function p() which will call the siglongjmp()
+		 * function
+		 */
+		p();
+
+		printf("control returning here is an error\n");
+		result=-1;
+		break;
+	case -1:
+		printf("siglongjmp() function was called\n");
+
+		/* Retrieve the current signal mask */
+
+		sigprocmask(SIG_SETMASK, NULL, &sigset);
+
+		/* Verify SIGUSR2 is in sigset */
+		if(sigismember(&sigset, SIGUSR2)) {
+			  printf("signal mask was restored after siglongjmp()\n");
+			  result=0;
+		} else {
+			  printf("signal mask was not restored after siglongjmp()\n");
+			  result=-1;
+		}
+		break;
+	default:
+		printf("this unexpected return code is an error\n");
+		result=-1;
+		break;
+	}
+
+	printf("return from main with result %d\n", result);
+
+	return result;
+}
+
+void p(void) {
+
+	struct sigaction sigact;
+	int error=0;
+
+	printf("performing function p()\n");
+
+	/* Setup signal handler in case error condition is detected */
+	sigemptyset(&sigact.sa_mask);
+	sigact.sa_flags = 0;
+	sigact.sa_handler = catcher;
+	sigaction(SIGUSR2, &sigact, NULL);
+
+	/*
+	 * Delete SIGUSR2 from the signal set that was initialized
+	 * by the main() function. This allows us to demonstrate
+	 * that the original signal set saved by the sigsetjmp() function
+	 * is restored by the siglongjmp() function.
+	 */
+	sigdelset(&sigset, SIGUSR2);
+	sigprocmask(SIG_SETMASK, &sigset, NULL);
+
+	/* After some processing an error condition is detected */
+	error=-1;
+
+	/* Call catcher() function if error is detected */
+	if(error != 0) {
+		catcherWasCalled = 0;
+
+		/* Send SIGUSR2 to handle the error condition */
+
+		printf("error condition detected, send SIGUSR2 signal\n");
+		kill(getpid(), SIGUSR2);
+
+		if(catcherWasCalled == 1) {
+			printf("catcher() function handled the error condition\n");
+
+			/*
+			 * Perform a nonlocal "goto" and specify -1 for the
+			 * return value
+			 */
+
+			siglongjmp(mark, -1);
+
+			printf("control getting here is an error\n");
+			exit(3);
+		}
+	}
+}
+
+void catcher(int signo) {
+	/*
+	 * Indicate the catcher() function is handling the
+	 * SIGUSR2 signal.
+	 */
+	catcherWasCalled = 1;
+}