CheckBufferOverrun: Skip warnings about array index out of bounds in unions. Theoretically, the array is at least as large as the biggest union member.

lib/checkbufferoverrun.cpp

@@ -1507,6 +1507,9 @@ void CheckBufferOverrun::bufferOverrun()
             if (var->dimension(0) <= 1 && Token::simpleMatch(var->nameToken()->linkAt(1),"] ; }"))
                 continue;
 
+            if (var->scope() && var->scope()->type == Scope::eUnion)
+                continue;
+
             ArrayInfo arrayInfo(var, symbolDatabase);
             arrayInfo.varname(varname);
 

test/testbufferoverrun.cpp

@@ -563,6 +563,12 @@ private:
               "    ab->a[0] = 0;\n"
               "}");
         ASSERT_EQUALS("", errout.str());
+
+        check("union { char a[1]; int b; } ab;\n"
+              "void f() {\n"
+              "    ab.a[2] = 0;\n"
+              "}");
+        ASSERT_EQUALS("", errout.str());
     }