Fix #12422 False positive: subtracting pointers in same struct

lib/checkother.cpp

@@ -3801,6 +3801,8 @@ void CheckOther::checkComparePointers()
                 continue;
             if (v1.tokvalue->varId() == v2.tokvalue->varId())
                 continue;
+            if (var1->scope() == var2->scope() && var1->scope()->isClassOrStructOrUnion())
+                continue;
             if (var1->isReference() || var2->isReference())
                 continue;
             if (var1->isRValueReference() || var2->isRValueReference())

test/testother.cpp

@@ -11549,7 +11549,6 @@ class TestOther : public TestFixture {
               "    return xp > yp;\n"
               "}");
         ASSERT_EQUALS(
-            "[test.cpp:1] -> [test.cpp:5] -> [test.cpp:1] -> [test.cpp:6] -> [test.cpp:7]: (error) Comparing pointers that point to different objects\n"
             "[test.cpp:5]: (style) Variable 'xp' can be declared as pointer to const\n"
             "[test.cpp:6]: (style) Variable 'yp' can be declared as pointer to const\n"
             "[test.cpp:5]: (style) Variable 'xp' can be declared as pointer to const\n" // duplicate
@@ -11646,6 +11645,15 @@ class TestOther : public TestFixture {
               "}\n");
         ASSERT_EQUALS("[test.cpp:1] -> [test.cpp:3] -> [test.cpp:2] -> [test.cpp:3] -> [test.cpp:3]: (error) Subtracting pointers that point to different objects\n",
                       errout.str());
+
+        check("struct S {\n" // #12422
+              "    int a, b;\n"
+              "};\n"
+              "void f() {\n"
+              "    S s{};\n"
+              "    size_t x = static_cast<size_t>(reinterpret_cast<char*>(&s.b) - reinterpret_cast<char*>(&s.a));\n"
+              "}\n");
+        ASSERT_EQUALS("", errout.str());
     }
 
     void unusedVariableValueTemplate() {