https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104944
Bug ID: 104944
Summary: incorrect alignas(void) accepted (with warning if
templated)
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: gccbugbjorn at fahller dot se
Target Milestone: ---
The erroneous code:
struct alignas(void) S{};
Is accepted without any diagnostic with g++
(Compiler-Explorer-Build-gcc-98cd717fca9f21625b9c79c9231c2e909d1d93a3-binutils-2.36.1)
12.0.1 20220306 (experimental)
https://godbolt.org/z/q7das4G1W
With 'void' coming from a template, a confusing warning is issued:
template <typename T>
struct alignas(T) S {};
S<void> s;
The message is:
In instantiation of 'struct S<void>':
<source>:4:9: required from here
<source>:2:16: warning: invalid application of '__alignof__' to a void type
[-Wpointer-arith]
2 | struct alignas(T) S {};
| ^
This is not entirely incorrect, but I believe most programmers would recognize
that they have no `__alignof__` in their code, nor any pointer arithmetics.
