msvcrt: Update size checks for secure scanf versions.

dlls/msvcrt/scanf.h

@@ -548,13 +548,13 @@ _FUNCTION_ {
                     while (width && (nch != _EOF_))
                     {
                         if (!suppress) {
-                            *str++ = _CHAR2SUPPORTED_(nch);
                             if(size) size--;
                             else {
                                 _UNLOCK_FILE_(file);
                                 *pstr = 0;
                                 return rd;
                             }
+                            *str++ = _CHAR2SUPPORTED_(nch);
                         }
                         st++;
                         width--;
@@ -574,13 +574,13 @@ _FUNCTION_ {
                     while (width && (nch != _EOF_))
                     {
                         if (!suppress) {
-                            *str++ = _WIDE2SUPPORTED_(nch);
                             if(size) size--;
                             else {
                                 _UNLOCK_FILE_(file);
                                 *pstr = 0;
                                 return rd;
                             }
+                            *str++ = _WIDE2SUPPORTED_(nch);
                         }
                         st++;
                         width--;

dlls/msvcrt/tests/scanf.c

@@ -282,10 +282,17 @@ static void test_sscanf_s(void)
     ok(ret == 0, "Wrong number of arguments read: %d\n", ret);
     ok(buf[0]=='\0', "buf = %s\n", buf);
 
-    buf[0] = 'a';
+    memset(buf, 'a', sizeof(buf));
     ret = psscanf_s("123", "%3c", buf, 2);
     ok(ret == 0, "Wrong number of arguments read: %d\n", ret);
     ok(buf[0]=='\0', "buf = %s\n", buf);
+    ok(buf[1]=='2', "buf[1] = %d\n", buf[1]);
+    ok(buf[2]=='a', "buf[2] = %d\n", buf[2]);
+
+    buf[3] = 'a';
+    buf[4] = 0;
+    ret = psscanf_s("123", "%3c", buf, 3);
+    ok(!strcmp("123a", buf), "buf = %s\n", buf);
 
     i = 1;
     ret = psscanf_s("123 123", "%s %d", buf, 2, &i);