https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122360
Bug ID: 122360
Summary: Initialized variable is reported as uninitialized when
reading through a reinterpret_cast-ed pointer
Product: gcc
Version: 12.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: csaba_22 at yahoo dot co.uk
Target Milestone: ---
When compiled with -O2 -Wall -Wno-strict-aliasing, the following code
#include <stdint.h>
uint8_t sum()
{
uint64_t dw = 42ul;
uint32_t wo = reinterpret_cast<uint32_t*>(&dw)[0] +
reinterpret_cast<uint32_t*>(&dw)[1];
uint16_t hw = reinterpret_cast<uint16_t*>(&wo)[0] +
reinterpret_cast<uint16_t*>(&wo)[1];
uint16_t bb = reinterpret_cast<uint8_t *>(&hw)[0] +
reinterpret_cast<uint8_t *>(&hw)[1];
return bb;
}
reports 'dw' is used uninitialized, even though dw is declared with an
initializer.
https://godbolt.org/z/GKK9xsrP8
Originally detected with RedHat's GCC 12.2.1; same behavior with GCC 12.5 on
godbolt.
