diff --git a/src/doc/unstable-book/src/language-features/lang-items.md b/src/doc/unstable-book/src/language-features/lang-items.md index 6f096e582f5..b6e61e7050c 100644 --- a/src/doc/unstable-book/src/language-features/lang-items.md +++ b/src/doc/unstable-book/src/language-features/lang-items.md @@ -248,7 +248,6 @@ the source code. - `eh_personality`: `libpanic_unwind/gcc.rs` (GNU) - `eh_personality`: `libpanic_unwind/seh.rs` (SEH) - `eh_unwind_resume`: `libpanic_unwind/gcc.rs` (GCC) - - `eh_catch_typeinfo`: `libpanic_unwind/seh.rs` (SEH) - `eh_catch_typeinfo`: `libpanic_unwind/emcc.rs` (EMCC) - `panic`: `libcore/panicking.rs` - `panic_bounds_check`: `libcore/panicking.rs` diff --git a/src/libpanic_unwind/seh.rs b/src/libpanic_unwind/seh.rs index da5ee5369e0..f599f9815a6 100644 --- a/src/libpanic_unwind/seh.rs +++ b/src/libpanic_unwind/seh.rs @@ -167,6 +167,9 @@ pub struct _TypeDescriptor { // Note that we intentionally ignore name mangling rules here: we don't want C++ // to be able to catch Rust panics by simply declaring a `struct rust_panic`. +// +// When modifying, make sure that the type name string exactly matches +// the one used in src/librustc_codegen_llvm/intrinsic.rs. const TYPE_NAME: [u8; 11] = *b"rust_panic\0"; static mut THROW_INFO: _ThrowInfo = _ThrowInfo { @@ -199,12 +202,12 @@ extern "C" { static TYPE_INFO_VTABLE: *const u8; } -// We use #[lang = "eh_catch_typeinfo"] here as this is the type descriptor which -// we'll use in LLVM's `catchpad` instruction which ends up also being passed as -// an argument to the C++ personality function. +// This type descriptor is only used when throwing an exception. The catch part +// is handled by the try intrinsic, which generates its own TypeDescriptor. // -// Again, I'm not entirely sure what this is describing, it just seems to work. -#[cfg_attr(not(test), lang = "eh_catch_typeinfo")] +// This is fine since the MSVC runtime uses string comparison on the type name +// to match TypeDescriptors rather than pointer equality. +#[cfg_attr(bootstrap, lang = "eh_catch_typeinfo")] static mut TYPE_DESCRIPTOR: _TypeDescriptor = _TypeDescriptor { pVFTable: unsafe { &TYPE_INFO_VTABLE } as *const _ as *const _, spare: core::ptr::null_mut(), diff --git a/src/librustc_codegen_llvm/intrinsic.rs b/src/librustc_codegen_llvm/intrinsic.rs index fa89c630345..fa7e7e6e4a2 100644 --- a/src/librustc_codegen_llvm/intrinsic.rs +++ b/src/librustc_codegen_llvm/intrinsic.rs @@ -954,6 +954,31 @@ fn codegen_msvc_try( let cs = catchswitch.catch_switch(None, None, 1); catchswitch.add_handler(cs, catchpad.llbb()); + // We can't use the TypeDescriptor defined in libpanic_unwind because it + // might be in another DLL and the SEH encoding only supports specifying + // a TypeDescriptor from the current module. + // + // However this isn't an issue since the MSVC runtime uses string + // comparison on the type name to match TypeDescriptors rather than + // pointer equality. + // + // So instead we generate a new TypeDescriptor in each module that uses + // `try` and let the linker merge duplicate definitions in the same + // module. + // + // When modifying, make sure that the type_name string exactly matches + // the one used in src/libpanic_unwind/seh.rs. + let type_info_vtable = bx.declare_global("??_7type_info@@6B@", bx.type_i8p()); + let type_name = bx.const_bytes(b"rust_panic\0"); + let type_info = + bx.const_struct(&[type_info_vtable, bx.const_null(bx.type_i8p()), type_name], false); + let tydesc = bx.declare_global("__rust_panic_type_info", bx.val_ty(type_info)); + unsafe { + llvm::LLVMRustSetLinkage(tydesc, llvm::Linkage::LinkOnceODRLinkage); + llvm::SetUniqueComdat(bx.llmod, tydesc); + llvm::LLVMSetInitializer(tydesc, type_info); + } + // The flag value of 8 indicates that we are catching the exception by // reference instead of by value. We can't use catch by value because // that requires copying the exception object, which we don't support @@ -961,12 +986,7 @@ fn codegen_msvc_try( // // Source: MicrosoftCXXABI::getAddrOfCXXCatchHandlerType in clang let flags = bx.const_i32(8); - let tydesc = match bx.tcx().lang_items().eh_catch_typeinfo() { - Some(did) => bx.get_static(did), - None => bug!("eh_catch_typeinfo not defined, but needed for SEH unwinding"), - }; let funclet = catchpad.catch_pad(cs, &[tydesc, flags, slot]); - let i64_align = bx.tcx().data_layout.i64_align.abi; let payload_ptr = catchpad.load(slot, ptr_align); let payload = catchpad.load(payload_ptr, i64_align);