ASDenysPetrov added a comment.
In D106681#3075337 <https://reviews.llvm.org/D106681#3075337>, @steakhal wrote:
> I just wanted you to think about these cases.
> BTW this should work for **L1646**:
>
> extern const int arr[]; // Incomplete array type
> void top() {
> (void)arr[42];
> }
Yes this will work for **L1646**. But I've already added similar tests for this
line: `glob_array_index4` and `struct_arr_index1` functions in
//initialization.cpp//. I mean it doesn't matter whether it is an incomplete or
complete type.
================
Comment at: clang/test/Analysis/initialization.c:103
+void glob_arr_index4() {
+ clang_analyzer_eval(glob_arr_no_init[2]); // expected-warning{{UNKNOWN}}
+}
----------------
steakhal wrote:
> I'm pretty sure we should not get `Unknown` for simply loading from a global
> variable.
> That would imply that loading two times subsequently we could not prove that
> the value remained the same.
> But that should remain the same, thus compare equal unless some other code
> modifier that memory region.
>
> That could happen for two reasons:
> 1) There is a racecondition, and another thread modified that location. But
> that would be UB, so that could not happen.
> 2) The global variable is //volatile//, so the hardware might changed its
> content- but this global is not volatile so this does not apply.
>
> That being said, this load should have resulted in a //fresh// conjured
> symbolic value instead of //unknown//.
> Could you please check if it did result in //unknown// before your patch, or
> you did introduce this behavior?
I'm not sure I caught your thoughts.
But I think the things is much simplier:
`clang_analyzer_eval` can only produce `UNKNOWN` or `TRUE` or `FALSE`. If we
know the constraint of `glob_arr_no_init[2]` we return `TRUE` or `FALSE`, and
`UNKNOWN` otherwise.
But in fact I should use `clang_analyzer_dump` here instead of
`clang_analyzer_eval`. This is actually my fault. I'll update this.
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D106681/new/
https://reviews.llvm.org/D106681
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