https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109283
Steven Sun <StevenSun2021 at hotmail dot com> changed:
What |Removed |Added
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CC| |StevenSun2021 at hotmail dot
com
--- Comment #1 from Steven Sun <StevenSun2021 at hotmail dot com> ---
It is indeed a bug. I currently only investigated into the gcc-12, it generates
something for
```
struct S{ /**/ };
bool w;
co_yield w ? S{"a"} : S{"b"};
```
pseudo-code for the generated gimple:
```
char __res[sizeof(S)];
char __a[sizeof(S)];
char __b[sizeof(S)];
new (__a) S("a");
new (__b) S("b");
if (w)
memcpy(__res, __a, sizeof(S));
else
memcpy(__res, __b, sizeof(S));
/*
...
*/
__b->~S();
__a->~S();
__c->~S();
```
So, clearly there is at least 3 bugs here:
i. `__res` is never constructed.
ii. only one of the `__a` and `__b` should be constructed, not both.
iii. the assignment is not corrected (it uses `gimple_assign` for value copy).
If the ii is correctly implemented, iii will not happen.
Though, the code will work fine on all trivial types.
The correct code should be
```
char __res[sizeof(S)];
if (w)
new (__res) S("a");
else
new (__res) S("b");
/*
...
*/
__res->~S();
```
