On 6/29/23 13:22, Olivier Dion wrote:
On Thu, 22 Jun 2023, "Paul E. McKenney" <paul...@kernel.org> wrote:
On Thu, Jun 22, 2023 at 11:55:55AM -0400, Mathieu Desnoyers wrote:
On 6/21/23 19:19, Paul E. McKenney wrote:
I suggest C11 volatile atomic load/store. Load/store fusing is permitted
for non-volatile atomic loads and stores, and such fusing can ruin your
code's entire day. ;-)
After some testing, I got a wall of warnings:
-Wignored-qualifiers:
Warn if the return type of a function has a type qualifier such as
"const". For ISO C such a type qualifier has no effect, since the
value returned by a function is not an lvalue. For C++, the warning
is only emitted for scalar types or "void". ISO C prohibits
qualified "void" return types on function definitions, so such
return types always receive a warning even without this option.
Since we are using atomic builtins, for example load:
type __atomic_load_n (type *ptr, int memorder)
If we put the qualifier volatile to TYPE, we end up with the same
qualifier on the return value, triggering a warning for each atomic
operation.
This seems to be only a problem when compiling in C++ [0] while in C it
seems the compiler is more relaxed on this [1].
Ideas to make the toolchains happy? :-)
Change:
(__typeof__(*ptr) *volatile)(ptr);
(which applies the volatile to the pointer, rather than what is pointed to)
to either:
(volatile __typeof__(*ptr) *)(ptr);
or:
(__typeof__(*ptr) volatile *)(ptr);
Thanks,
Mathieu
[0] https://godbolt.org/z/3nW14M3v1
[1] https://godbolt.org/z/TcTeMeKbW
--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com
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