[PATCH] D103440: [WIP][analyzer] Introduce range-based reasoning for addition operator

[Valeriy Savchenko via Phabricator via cfe-commits]

vsavchenko added a comment.

I also would like to see tests where the ranges are not going all the way to either `INT_MIN` or `INT_MAX` (if we talk about `int`), but overflow still might happen, and cases where overflow might happen, but we still can identify the overflowing results precisely (e.g. the result is `[INT_MIN, INT_MIN + 10] and [INT_MAX - 5, INT_MAX])



================
Comment at: clang/test/Analysis/constant-folding.c:279
+    if (c == INT_MIN && d == INT_MIN) {
+      clang_analyzer_eval((c + d) == 0); // expected-warning{{TRUE}}
+    }
----------------
Good!


================
Comment at: clang/test/Analysis/constant-folding.c:282
+
+    if (c >= -20 && d >= -40) {
+      clang_analyzer_eval((c + d) < -1); // expected-warning{{TRUE}}
----------------
Great, it's good to check negative numbers.
I have one note here.  The fact that we don't have a testing framework and use this approach of inspecting the actual analysis has an interesting implication.

```
if (a == 10) { // here we split path into 2 paths: one where a == 10, and one where a != 10;
               // one goes inside of if, one doesn't
  . . .
}
if (a >= 5) { // here we split into 3 paths: a == 10, a < 5, and a in [5, 9] and [11, INT_MAX] (aka a >= 5 and a != 10).
              // 1 path was infeasible: a == 10 and a < 5
              // Two of these paths go inside of the if, one doesn't
  . . .
  clang_analyzer_eval(a == 10); // it will produce two results: TRUE and FALSE
}
clang_analyzer_eval(a == 10); // it will produce three results: TRUE, FALSE, and FALSE
```

We don't want to test how path splitting works in these particular tests (they are about solver and constant folding after all), that's why we try to have only one path going through each `clang_analyzer_eval(...)`

In this example, you still have residual paths where `c != INT_MIN`, `c == INT_MIN and d != INT_MIN`, and `c == INT_MIN and d == INT_MIN`.


================
Comment at: clang/test/Analysis/constant-folding.c:304-305
+  if (c > 0 && d > 0) {
+    clang_analyzer_eval((c + d) > 1); // expected-warning{{TRUE}}
+    clang_analyzer_eval((c + d) < -1); // expected-warning{{TRUE}}
+  }
----------------
How can these two statements be TRUE at the same time?


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https://reviews.llvm.org/D103440