[PATCH] c++: Fix crash during NRV optimization with invalid input [PR117099]

[Simon Martin]

On 18 Oct 2024, at 10:55, Sam James wrote:

> Simon Martin <simon@nasilyan.com> writes:
>
>> Hi Sam,
>
> Hi Simon,
>
>>
>> On 16 Oct 2024, at 22:06, Sam James wrote:
>>
>>> Simon Martin <simon@nasilyan.com> writes:
>>>
>>>> We ICE upon the following invalid code because we end up calling
>>>> finalize_nrv_r with a RETURN_EXPR with no operand.
>>>>
>>>> === cut here ===
>>>> struct X {
>>>>   ~X();
>>>> };
>>>> X test(bool b) {
>>>>   {
>>>>     X x;
>>>>     return x;
>>>>   }
>>>>   if (!(b)) return;
>>>> }
>>>> === cut here ===
>>>>
>>>> This patch fixes this by simply returning error_mark_node when
>>>> detecting
>>>> a void return in a function returning non-void.
>>>>
>>>> Successfully tested on x86_64-pc-linux-gnu.
>>>>
>>>> 	PR c++/117099
>>>>
>>>> gcc/cp/ChangeLog:
>>>>
>>>> 	* typeck.cc (check_return_expr): Return error_mark_node upon
>>>> 	void return for function returning non-void.
>>>>
>>>> gcc/testsuite/ChangeLog:
>>>>
>>>> 	* g++.dg/parse/crash77.C: New test.
>>>>
>>>> ---
>>>>  gcc/cp/typeck.cc                     |  1 +
>>>>  gcc/testsuite/g++.dg/parse/crash77.C | 14 ++++++++++++++
>>>>  2 files changed, 15 insertions(+)
>>>>  create mode 100644 gcc/testsuite/g++.dg/parse/crash77.C
>>>>
>>>> diff --git a/gcc/cp/typeck.cc b/gcc/cp/typeck.cc
>>>> index 71d879abef1..22a6ec9a185 100644
>>>> --- a/gcc/cp/typeck.cc
>>>> +++ b/gcc/cp/typeck.cc
>>>> @@ -11238,6 +11238,7 @@ check_return_expr (tree retval, bool
>>>> *no_warning, bool *dangling)
>>>>  	 RETURN_EXPR to avoid control reaches end of non-void function
>>>>  	 warnings in tree-cfg.cc.  */
>>>>        *no_warning = true;
>>>> +      return error_mark_node;
>>>>      }
>>>>    /* Check for a return statement with a value in a function that
>>>>       isn't supposed to return a value.  */
>>>> diff --git a/gcc/testsuite/g++.dg/parse/crash77.C
>>>> b/gcc/testsuite/g++.dg/parse/crash77.C
>>>> new file mode 100644
>>>> index 00000000000..d3f0ae6a877
>>>> --- /dev/null
>>>> +++ b/gcc/testsuite/g++.dg/parse/crash77.C
>>>> @@ -0,0 +1,14 @@
>>>> +// PR c++/117099
>>>> +// { dg-compile }
>>>
>>> dg-do compile
>>>
>> Aarg, of course, thanks for spotting this! Fixed in the attached
>> version.
>>
>>>> +
>>>> +struct X {
>>>> +  ~X();
>>>> +};
>>>> +
>>>> +X test(bool b) {
>>>> +  {
>>>> +    X x;
>>>> +    return x;
>>>> +  }
>>>> +  if (!(b)) return; // { dg-error "return-statement with no value" }
>>>> +}
>>>> -- 
>>>> 2.44.0
>>>>
>>>
>>> BTW, the line-endings on this seem a bit odd. Did you use
>>> git-send-email?
>> I did use git-send-email indeed. What oddities do you see with line
>> endings?
>> cat -A over the patch file looks good.
>>
>
> Weird -- if I open your original email in mu4e, I see a bunch of ^M at
> the end of the lines.
Strange. FWIW I’m generating and sending the patches from a MacOS box,
and there might be some weirdness coming from that. I’ll check and try
to fix.

Simon