[PATCH] Implement throw in conditional operator

[Richard Smith]

+    const QualType SubExprType = ThrowExpr->getSubExpr()->getType();

This is the wrong type; we want the type of the surrounding conditional
operator here, not the type of the exception.

I've committed a fix based on your patch in r211388. Thanks!


On Mon, Jun 16, 2014 at 9:37 AM, Marius Wachtler <undingen at gmail.com> wrote:

> Gentle ping..
> I updated the patch to target latest the svn revision and added an regexpr
> to check that "val" is really returned.
> Thank you
>
>
>
> On Wed, Jun 11, 2014 at 11:18 PM, Marius Wachtler <undingen at gmail.com>
> wrote:
>
>> Sorry for all the spam...
>> I attached the wrong patch file.
>>
>>
>>
>> On Wed, Jun 11, 2014 at 11:16 PM, Marius Wachtler <undingen at gmail.com>
>> wrote:
>>
>>> Thanks for your expertise.
>>> Attached you can find an updated patch where I removed the const and
>>> made the FileCheck a little bit more specific.
>>>
>>>
>>>
>>> On Wed, Jun 11, 2014 at 10:55 PM, Richard Smith <richard at metafoo.co.uk>
>>> wrote:
>>>
>>>> On Wed, Jun 11, 2014 at 1:25 PM, Marius Wachtler <undingen at gmail.com>
>>>> wrote:
>>>>
>>>>> Hi
>>>>>
>>>>> I added a testcase for the function you mention but I also added const
>>>>> to the return type because otherwise gcc won't compile it ("error: invalid
>>>>> initialization of non-const reference of type ‘int&’ from an rvalue of type
>>>>> ‘int’") - clang compiles both.
>>>>>
>>>>
>>>> GCC doesn't implement one of the relevant DRs; you don't need to make
>>>> the testcase work with it.
>>>>
>>>> The generated code from clang for the function looks correct and works
>>>>> as I would expect it.
>>>>> Compiling it with g++ 4.8.2 and -O2 will instead produce and object
>>>>> which will return an address to a temporary in the function and not a
>>>>> reference to the global val.
>>>>>
>>>>> I'm not sure if clangs behavior is correct or if it should also only
>>>>> accept a const reference? If the error is somewhere else I would appreciate
>>>>> some guidance to where to look around and what the expected behavior is.
>>>>>
>>>>
>>>> See http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#1550;
>>>> Clang's behavior is right, this is just a bug with IR generation.
>>>>
>>>> The C++11 non final standard I have says (5.16-2):
>>>>> "If either the second or the third operand has type (possibly
>>>>> cv-qualified) void, then the lvalue-to-rvalue (4.1), array-to-pointer (4.2),
>>>>> and function-to-pointer (4.3) standard conversions are performed on the
>>>>> second and third operands, and one of the following shall hold:
>>>>> — The second or the third operand (but not both) is a throw-expression
>>>>> (15.1); the result is of the type
>>>>> of the other and is a prvalue.
>>>>> — Both the second and the third operands have type void; the result is
>>>>> of type void and is a prvalue. [ Note: This includes the case where both
>>>>> operands are throw-expressions. — end note ]
>>>>> "
>>>>> So this means gcc is correct?
>>>>>
>>>>> Thank you very much
>>>>> - Marius
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> On Wed, Jun 11, 2014 at 1:05 AM, Richard Smith <richard at metafoo.co.uk>
>>>>> wrote:
>>>>>
>>>>>> Please also include a test that the produced lvalue actually has the
>>>>>> right value. Something like:
>>>>>>
>>>>>> int &test7(bool cond) {
>>>>>>   return cond ? throw 1 : val;
>>>>>> }
>>>>>>
>>>>>> ... and check that the value returned is @_Z3val
>>>>>>
>>>>>> On Tue, Jun 10, 2014 at 3:01 PM, Marius Wachtler <undingen at gmail.com>
>>>>>> wrote:
>>>>>>
>>>>>>> Hi
>>>>>>> Attached you can find an updates patch.
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On Tue, Jun 10, 2014 at 11:50 PM, David Majnemer <
>>>>>>> david.majnemer at gmail.com> wrote:
>>>>>>>
>>>>>>>> +
>>>>>>>>> +  case Expr::CXXThrowExprClass: {
>>>>>>>>> +    const auto* throwExpr = cast<CXXThrowExpr>(E);
>>>>>>>>>
>>>>>>>>
>>>>>>>> Please stick the star on the RHS. Also, it is customary in LLVM and
>>>>>>>> clang to spell it like "ThrowExpr"
>>>>>>>>
>>>>>>>>
>>>>>>>>> +    EmitCXXThrowExpr(throwExpr);
>>>>>>>>> +    const QualType subExprType =
>>>>>>>>> throwExpr->getSubExpr()->getType();
>>>>>>>>>
>>>>>>>>
>>>>>>>> Likewise for "subExprType"
>>>>>>>>
>>>>>>>> +    llvm::Type *Ty =
>>>>>>>>> llvm::PointerType::getUnqual(ConvertType(subExprType));
>>>>>>>>> +    return MakeAddrLValue(llvm::UndefValue::get(Ty), subExprType);
>>>>>>>>>    }
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> On Tue, Jun 10, 2014 at 5:19 PM, Marius Wachtler <
>>>>>>>> undingen at gmail.com> wrote:
>>>>>>>>
>>>>>>>>> Hello
>>>>>>>>>
>>>>>>>>> Attached you can find my first clang patch which should implement
>>>>>>>>> "cond ? throw 1 : val".
>>>>>>>>>
>>>>>>>>> Without this patch I get: "cannot compile this l-value expression
>>>>>>>>> yet"
>>>>>>>>>
>>>>>>>>> As this is my first time looking under the hood of clang I'm not
>>>>>>>>> sure if this is the right approach. I'm Looking forward to your feedback.
>>>>>>>>>
>>>>>>>>> - Marius Wachtler
>>>>>>>>>
>>>>>>>>> _______________________________________________
>>>>>>>>> cfe-commits mailing list
>>>>>>>>> cfe-commits at cs.uiuc.edu
>>>>>>>>> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> cfe-commits mailing list
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>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>
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