================
@@ -1870,6 +1870,28 @@ bool Sema::IsFunctionConversion(QualType FromType,
QualType ToType,
FromFn = QT->getAs<FunctionType>();
Changed = true;
}
+
+ // For C, when called from checkPointerTypesForAssignment,
+ // we need not to alter FromFn, or else even an innocuous cast
+ // like dropping effects will fail. In C++ however we do want to
+ // alter FromFn. TODO: Is this correct?
+ if (getLangOpts().CPlusPlus) {
+ FromFPT =
+ dyn_cast<FunctionProtoType>(FromFn); // in case FromFn changed above
----------------
Sirraide wrote:
No, that one’s different.
The point here is that `cast` asserts if the value you’re casting is-not-a the
type you’re casting to, whereas `dyn_cast` returns `nullptr`. As a result, the
intended way to use `dyn_cast` is to follow it with a check to see if it
returned `nullptr`; in this case, however, the next line immediately uses the
result of the cast without doing any checks whatsoever, so this would just
crash if `dyn_cast` returned null, whereas `cast` would instead assert, which
is what we want. In other words, if you’re not doing null checks, you want to
use `cast` instead of `dyn_cast`.
In this case, we’re in C++ mode (because of the surrounding `if`), so we should
never have prototypeless functions; that means a `cast` here should be fine.
https://github.com/llvm/llvm-project/pull/84983
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