https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104386
Bug ID: 104386
Summary: no_unique_address causes invalid member alignment of
pod struct
Product: gcc
Version: 11.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: gcc at ebasoft dot com.pl
Target Milestone: ---
struct base
{ [[no_unique_address]]
uint32_t x; std::byte v;
};
struct foo : public base
{ std::byte z; };
gcc sizeof(foo) == 8 https://godbolt.org/z/G4Mo3PdKT
clang sizeof(foo) == 12 https://godbolt.org/z/bdzvaMn9c
As I was told it is gcc bug
https://www.reddit.com/r/cpp/comments/sjx2mk/no_unique_addres_where_can_in_c_standard_instead/
[orbital1337]"Your class base is a POD but its not a POD for the purpose of
layout (since it has potentially overlapping data members). Thus the Itanium
ABI specifies that it's size without padding (dsize) should be set to its size
with padding (sizeof). The first datamember of your class foo is put at
dsize(base). clang does the right thing and puts it at an offset of 8 bytes
whereas gcc ignores that one line of the specification and puts it at an offset
of 5 bytes instead."
