Files
rust/tests/codegen-llvm
Matthias Krüger ffba05ee29 Rollup merge of #146865 - folkertdev:kcfi-only-reify-dyn-compatible, r=rcvalle
kcfi: only reify trait methods when dyn-compatible

fixes https://github.com/rust-lang/rust/issues/146853

Only generate a `ReifyShim` for trait method calls if the trait is dyn-compatible.

Until now kcfi would generate a `ReifyShim` whenever a trait method was cast to a function pointer. But technically the shim is only needed for dyn-compatible traits (where the method might end up in a vtable).

Up to this point that was only slightly inefficient, but in combination with c-variadic trait methods it is wrong. For c-variadic trait methods the generated shim is incorrect, and that is why c-variadic methods make a trait no longer dyn-compatible: we should simply never generate a `ReifyShim` that is c-variadic.

With this change the documentation on `ReifyReason` is now actually correct:

>  If KCFI is enabled, creating a function pointer from a method on a dyn-compatible trait. This includes the case of converting `::call`-like methods on closure-likes to function pointers.

cc ```@maurer``` ```@workingjubilee```

r? ```@rcvalle```
2025-10-07 19:39:06 +02:00
..
2025-08-15 16:42:21 +00:00
2025-08-20 16:35:33 +02:00

The files here use the LLVM FileCheck framework, documented at https://llvm.org/docs/CommandGuide/FileCheck.html.

One extension worth noting is the use of revisions as custom prefixes for FileCheck. If your codegen test has different behavior based on the chosen target or different compiler flags that you want to exercise, you can use a revisions annotation, like so:

// revisions: aaa bbb
// [bbb] compile-flags: --flags-for-bbb

After specifying those variations, you can write different expected, or explicitly unexpected output by using <prefix>-SAME: and <prefix>-NOT:, like so:

// CHECK: expected code
// aaa-SAME: emitted-only-for-aaa
// aaa-NOT:                        emitted-only-for-bbb
// bbb-NOT:  emitted-only-for-aaa
// bbb-SAME:                       emitted-only-for-bbb