research st, add test for setjmp and longjmp.

+/*
+# http://blog.csdn.net/win_lin/article/details/40948277
+# for all supports setjmp and longjmp:
+    g++ -g -O0 -o jmp_2flow jmp_2flow.cpp
+*/
+#include <stdio.h>
+#include <stdlib.h>
+#include <setjmp.h>
+
+jmp_buf context_thread_0;
+jmp_buf context_thread_1;
+
+void thread0_functions()
+{
+    int ret = setjmp(context_thread_0);
+    // when ret is 0, create thread,
+    // when ret is not 0, longjmp to this thread.
+    if (ret == 0) {
+        return;
+    }
+    
+    int age = 10000;
+    const char* name = "winlin";
+    printf("[thread0] age=%d, name=%s\n", age, name);
+    if (!setjmp(context_thread_0)) {
+        printf("[thread0] switch to thread1\n");
+        longjmp(context_thread_1, 1);
+    }
+    
+    // crash, for the stack is modified by thread1.
+    // name = 0x2b67004009c8 <error: Cannot access memory at address 0x2b67004009c8>
+    printf("[thread0] terminated, age=%d, name=%s\n", age, name);
+    exit(0);
+}
+
+void thread1_functions()
+{
+    int ret = setjmp(context_thread_1);
+    // when ret is 0, create thread,
+    // when ret is not 0, longjmp to this thread.
+    if (ret == 0) {
+        return;
+    }
+    
+    int age = 11111;
+    printf("[thread1] age=%d\n", age);
+    if (!setjmp(context_thread_1)) {
+        printf("[thread1] switch to thread0\n");
+        longjmp(context_thread_0, 1);
+    }
+    
+    printf("[thread1] terminated, age=%d\n", age);
+    exit(0);
+}
+
+int main(int argc, char** argv) 
+{
+    thread0_functions();
+    thread1_functions();
+    
+    // kickstart
+    longjmp(context_thread_0, 1);
+    
+    return 0;
+}

 /*
+# http://blog.csdn.net/win_lin/article/details/40948277
 # for all supports setjmp and longjmp:
     g++ -g -O0 -o jmp_flow jmp_flow.cpp
 */