[clang] [clang-tools-extra] RFC: [clang-tidy] [analyzer] Nondeterministic pointer usage improvements (PR #110471)

[via cfe-commits]

================
@@ -0,0 +1,69 @@
+// RUN: %check_clang_tidy %s bugprone-nondeterministic-pointer-usage %t -- -- -I%S -std=c++!4
+
+#include "Inputs/system-header-simulator-cxx.h"
+
+template<class T>
+void f(T x);
+
+void PointerIteration() {
+  int a = 1, b = 2;
+  std::set<int> OrderedIntSet = {a, b};
+  std::set<int *> OrderedPtrSet = {&a, &b};
+  std::unordered_set<int> UnorderedIntSet = {a, b};
+  std::unordered_set<int *> UnorderedPtrSet = {&a, &b};
+  std::map<int, int> IntMap = { std::make_pair(a,a), std::make_pair(b,b) };
+  std::map<int*, int*> PtrMap = { std::make_pair(&a,&a), std::make_pair(&b,&b) };
+  std::unordered_map<int, int> IntUnorderedMap = { std::make_pair(a,a), std::make_pair(b,b) };
+  std::unordered_map<int*, int*> PtrUnorderedMap = { std::make_pair(&a,&a), std::make_pair(&b,&b) };
+
+  for (auto i : OrderedIntSet) // no-warning
+    f(i);
+
+  for (auto i : OrderedPtrSet) // no-warning
+    f(i);
+
+  for (auto i : UnorderedIntSet) // no-warning
+    f(i);
+
+  for (auto i : UnorderedPtrSet) // CHECK-MESSAGES: warning: Iteration of pointers is nondeterministic [bugprone-nondeterministic-pointer-usage]
+    f(i);
+
+  for (auto &i : UnorderedPtrSet) // no-warning
+    f(i);
+
+  for (auto &i : IntMap) // no-warning
+    f(i);
+
+  for (auto &i : PtrMap) // no-warning
+    f(i);
+
+  for (auto &i : IntUnorderedMap) // no-warning
+    f(i);
+
+  for (auto &i : PtrUnorderedMap) // FALSE NEGATIVE!
+    f(i);
+}
+
+bool g (int *x) { return true; }
+bool h (int x) { return true; }
+
+void PointerSorting() {
+  int a = 1, b = 2, c = 3;
+  std::vector<int> V1 = {a, b};
+  std::vector<int *> V2 = {&a, &b};
+
+  std::is_sorted(V1.begin(), V1.end());                    // no-warning
+  std::nth_element(V1.begin(), V1.begin() + 1, V1.end());  // no-warning
+  std::partial_sort(V1.begin(), V1.begin() + 1, V1.end()); // no-warning
+  std::sort(V1.begin(), V1.end());                         // no-warning
+  std::stable_sort(V1.begin(), V1.end());                  // no-warning
+  std::partition(V1.begin(), V1.end(), h);                 // no-warning
+  std::stable_partition(V1.begin(), V1.end(), h);          // no-warning
+  std::is_sorted(V2.begin(), V2.end()); // CHECK-MESSAGES: warning: Sorting pointers is nondeterministic [bugprone-nondeterministic-pointer-usage]
----------------
whisperity wrote:

```suggestion
  std::is_sorted(V2.begin(), V2.end());
  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: Sorting pointers is nondeterministic [bugprone-nondeterministic-pointer-usage]
```

Clang-Tidy LIT files conventionally force the match against the line number (with relative numbers in the code wherever possible to facilitate later extension and shuffling-around) because the `// CHECK-MESSAGES:`, as present in the code right now, are not satisfactory enough to ensure that the right matches happen at the right locations. (`%check_clang_tidy` doesn't exactly works like `--verify` for CSA!)

https://github.com/llvm/llvm-project/pull/110471