std.cfg: Improved configuration for mbrlen() and extended test cases.

cfg/std.cfg

@@ -2312,6 +2312,7 @@
     </arg>
     <arg nr="3" direction="inout">
       <not-uninit/>
+      <not-null/>
     </arg>
   </function>
   <!-- wint_t btowc(int c); -->

test/cfg/std.c

@@ -1598,6 +1598,15 @@ void uninitvar_mbrlen(const char* p, size_t m, mbstate_t* s)
     (void)mbrlen(p,m,s);
 }
 
+void nullPointer_mbrlen(const char* p, size_t m, mbstate_t* s)
+{
+    /* no warning is expected: A call to the function with a null pointer as pmb resets the shift state (and ignores parameter max). */
+    (void)mbrlen(NULL,m,s);
+    (void)mbrlen(NULL,0,s);
+    /* cppcheck-suppress nullPointer */
+    (void)mbrlen(p,m,NULL);
+}
+
 void uninitvar_btowc(void)
 {
     int c;

test/cfg/std.cpp

@@ -1106,6 +1106,15 @@ void uninitvar_mbrlen(const char* p, size_t m, mbstate_t* s)
     (void)std::mbrlen(p,m,s);
 }
 
+void nullPointer_mbrlen(const char* p, size_t m, mbstate_t* s)
+{
+    // no warning is expected: A call to the function with a null pointer as pmb resets the shift state (and ignores parameter max).
+    (void)std::mbrlen(NULL,m,s);
+    (void)std::mbrlen(NULL,0,s);
+    // cppcheck-suppress nullPointer
+    (void)std::mbrlen(p,m,NULL);
+}
+
 void uninitvar_btowc(void)
 {
     int c;