我创建了一个基本函数Foo1
,通过调用调用另一个函数Bar2
。展开清理基本块中的第一条指令必须是着陆点:
void bar2()
{
throw;
}
llvm::Function* Bar2Fn = llvm::Function::Create( voidSig , &bar2);
engine->addGlobalMapping( Bar2Fn, (void*)&bar2 );
llvm::InvokeInst* inv = builder.CreateInvoke( Bar2Fn , continueBlock, unwindBlock, llvmArgValues , "invoke");
builder.CreateBr(continueBlock);
builder.SetInsertPoint(unwindBlock);
llvm::LandingPadInst* landPadInst = builder.CreateLandingPad(...);
//add some cleanup code? where??
我真的不知道我需要在CreateLandingPad
的参数之间放置什么才能获得一个基本的登陆平台,它可以调用当前Foo1
堆栈对象的自定义清理代码。 Bar2
可能通过调用自己抛出(或重新抛出现有异常)的c ++函数来抛出
答案 0 :(得分:6)
我承认我在这里没什么经验,但你看过异常演示代码示例了吗?它似乎包含了您希望找到的那种序列。
基本上,你首先要设置个性,就像在C ++中一样:
llvm::Function *personality = module.getFunction("__gxx_personality_v0");
然后,您创建具有该个性的登录牌并定义其类型:
llvm::LandingPadInst *caughtResult =
builder.CreateLandingPad(ourCaughtResultType,
personality,
numExceptionsToCatch,
"landingPad");
设置要捕获的类型:
for (unsigned i = 0; i < numExceptionsToCatch; ++i) {
// Set up type infos to be caught
caughtResult->addClause(module.getGlobalVariable(
ourTypeInfoNames[exceptionTypesToCatch[i]]));
}
并表示它是一个清理处理程序:
caughtResult->setCleanup(true);
我相信这就是它;现在你可以自己获得例外:
llvm::Value *unwindException = builder.CreateExtractValue(caughtResult, 0);
从中获取这些代码段的ExceptionDemo.cpp文件包含更完整的序列;具体来说,它显示了如何检查捕获的异常的类型根,并在匹配某些内容时分支到特定的块 - 清理代码:
llvm::Value *retTypeInfoIndex = builder.CreateExtractValue(caughtResult, 1);
// FIXME: Redundant storage which, beyond utilizing value of
// caughtResultStore for unwindException storage, may be alleviated
// altogether with a block rearrangement
builder.CreateStore(caughtResult, caughtResultStorage);
builder.CreateStore(unwindException, exceptionStorage);
builder.CreateStore(ourExceptionThrownState, exceptionCaughtFlag);
// Retrieve exception_class member from thrown exception
// (_Unwind_Exception instance). This member tells us whether or not
// the exception is foreign.
llvm::Value *unwindExceptionClass =
builder.CreateLoad(builder.CreateStructGEP(
builder.CreatePointerCast(unwindException,
ourUnwindExceptionType->getPointerTo()),
0));
// Branch to the externalExceptionBlock if the exception is foreign or
// to a catch router if not. Either way the finally block will be run.
builder.CreateCondBr(builder.CreateICmpEQ(unwindExceptionClass,
llvm::ConstantInt::get(builder.getInt64Ty(),
ourBaseExceptionClass)),
exceptionRouteBlock,
externalExceptionBlock);
最后,还提供了另一个示例以及解释on the blog post that introduced the new exception handling mechanism。