https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106446
Bug ID: 106446
Summary: -Warray-bounds false positive on downcast under
condition
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: coillol at yandex dot ru
Target Milestone: ---
Minimized example:
---
struct B { int x = 1; };
struct D1 : B {};
struct Data {
int val = 666;
};
struct D2 : Data, B {
static bool is_me(const B &b);
};
static int bar(const B &b) {
if (D2::is_me(b))
return static_cast<const D2 &>(b).val;
return 777;
};
int foo() {
return bar(D1{});
}
---
Compiling using `g++
(Compiler-Explorer-Build-gcc-789c4b9bb015c361bc1a6adfcd0abadce555e562-binutils-2.38)
13.0.0 20220725 (experimental)` with `-O2 -Wall` there is a warning:
--
In function 'int bar(const B&)',
inlined from 'int foo()' at <source>:20:13:
<source>:15:39: warning: array subscript 0 is outside array bounds of 'D1 [1]'
[-Warray-bounds]
15 | return static_cast<const D2 &>(b).val;
| ^~~
<source>: In function 'int foo()':
<source>:20:17: note: at offset -4 into object '<anonymous>' of size 4
20 | return bar(D1{});
|
--
Such behavior is observed with from gcc >= 10.1. Less minimized example --
https://godbolt.org/z/vb786jhfn -- can be reproduced only with gcc >= 12.1.
