[PATCH] D35110: [Analyzer] Constraint Manager Negates Difference

[Artem Dergachev via Phabricator via cfe-commits]

NoQ added inline comments.


================
Comment at: lib/StaticAnalyzer/Core/RangeConstraintManager.cpp:511
+           SSE->getLHS()->getType()->isSignedIntegerOrEnumerationType() ||
+           SSE->getLHS()->getType()->isPointerType()) {
+          return negV->Negate(BV, F);
----------------
baloghadamsoftware wrote:
> NoQ wrote:
> > Pointer types are currently treated as unsigned, so i'm not sure you want them here.
> For me it seems that pointer differences are still pointer types and they are signed. (The range becomes negative upon negative assumption. From test `ptr-arith.c`:
> 
> ```
> void use_symbols(int *lhs, int *rhs) {
>   clang_analyzer_eval(lhs < rhs); // expected-warning{{UNKNOWN}}
>   if (lhs < rhs)
>     return;
>   clang_analyzer_eval(lhs < rhs); // expected-warning{{FALSE}}
> 
>   clang_analyzer_eval(lhs - rhs); // expected-warning{{UNKNOWN}}
>   if ((lhs - rhs) != 5)
>     return;
>   clang_analyzer_eval((lhs - rhs) == 5); // expected-warning{{TRUE}}
> }
> ```
> 
> If I put `clang_analyzer_printState()` into the empty line in the middle, I get the following range for the difference: `[-9223372036854775808, 0]`. If I replace `int*` with `unsigned`, this range becomes `[0, 0]`, so `int*` is handled as a signed type here.
Umm, yeah, i was wrong.

*looks closer*

`T` is the type of the difference, right? I don't think i'd expect pointer type as the type of the difference.

Could you add test cases for pointers if you intend to support them (and maybe for unsigned types)?


https://reviews.llvm.org/D35110