#6569 Add strcasestr function to gnu.cfg

cfg/gnu.cfg

@@ -185,4 +185,19 @@
     </arg>
     <arg nr="6"/>
   </function>
+  <!-- https://www.gnu.org/software/gnulib/manual/html_node/c_002dstrcasestr.html -->
+  <!-- size_t strcasestr(const char *s1, const char *s2); -->
+  <function name="strcasestr">
+    <use-retval/>
+    <noreturn>false</noreturn>
+    <leak-ignore/>
+    <arg nr="1">
+      <not-null/>
+      <not-uninit/>
+    </arg>
+    <arg nr="2">
+      <not-null/>
+      <not-uninit/>
+    </arg>
+  </function>
 </def>

test/cfg/gnu.c

@@ -18,4 +18,7 @@ void leakReturnValNotUsed() {
    char* ptr2 = (char*)strndupa("test", 1);
    // cppcheck-suppress ignoredReturnValue
    strndupa("test", 1);
+   // cppcheck-suppress ignoredReturnValue
+   // cppcheck-suppress nullPointer
+   strcasestr("test", NULL);
 }