Re: [PATCH] c++, v2: Fix ICE during mangling of a conversion operator function template [PR126093]

On 8/18/26 3:34 AM, Jakub Jelinek wrote:
> On Tue, Aug 11, 2026 at 04:25:19PM -0400, Jason Merrill wrote:
>> On 8/7/26 8:45 AM, Jakub Jelinek wrote:
>>> We ICE when trying to mangle the TEMPLATE_DECL of a conversion operator,
>>> because FNDECL_USED_AUTO macro requires FUNCTION_DECL, but here we
>>> have a TEMPLATE_DECL instead.
>>> In this case, DECL_CONV_FN_TYPE contains the right type, so this patch
>>> just guards the FNDECL_USED_AUTO macro use on FUNCTION_DECLs.
>>
>> Hmm, if it's valid to get a TEMPLATE_DECL here I think we want to
>> STRIP_TEMPLATE earlier in the function to avoid the need for this; lots of
>> other things here seem to assume we're looking at the inner decl.
> 
> Ok, here is a different patch then to use STRIP_TEMPLATE before calling
> write_unqualified_name in the {class,function,variable,alias} template,
> concept, namespace alias and namespace (for the last two STRIP_TEMPLATE
> will do nothing, so I haven't moved it to a separate handling).
> 
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

OK.
> 2026-08-18  Jakub Jelinek  <[email protected]>
> 
> 	PR c++/126093
> 	* mangle.cc (write_reflection): Call write_unqualified_name on
> 	STRIP_TEMPLATE (arg) rather than just arg.
> 
> 	* g++.dg/reflect/mangle1.C: Add 2 new tests for reflections of
> 	conversion templates.
> 
> --- gcc/cp/mangle.cc.jj	2026-08-07 17:33:22.558549077 +0200
> +++ gcc/cp/mangle.cc	2026-08-17 19:57:43.384028251 +0200
> @@ -4302,7 +4302,7 @@ write_reflection (tree refl)
>   	   || strcmp (prefix, "ns") == 0)
>       {
>         write_prefix (decl_mangling_context (arg));
> -      write_unqualified_name (arg);
> +      write_unqualified_name (STRIP_TEMPLATE (arg));
>       }
>     else if (strcmp (prefix, "ba") == 0)
>       {
> --- gcc/testsuite/g++.dg/reflect/mangle1.C.jj	2026-08-07 17:33:22.564549003 +0200
> +++ gcc/testsuite/g++.dg/reflect/mangle1.C	2026-08-17 19:56:23.372630344 +0200
> @@ -15,6 +15,10 @@ struct S : B {
>     int : 0;
>     static int var;
>   };
> +struct Q {
> +  template <typename T>
> +  operator T () { return T (); }
> +};
>   struct W { union {}; union {}; union {}; union {}; };
>   template <auto> struct TCls {};
>   template <auto> void TFn ();
> @@ -65,6 +69,10 @@ namespace NS2 {
>     struct Z {
>     };
>     struct AA { int a, b; };
> +  struct Q {
> +    template <int N>
> +    operator int () { return N; }
> +  };
>   }
>   
>   constexpr auto ctx = std::meta::access_context::current ();
> @@ -147,6 +155,8 @@ baz (int x)
>     bar <241, ^^NS2::TCls> (); // class template
>     bar <250, ^^TFn> (); // function template
>     bar <251, ^^NS2::TFn> (); // function template
> +  bar <252, members_of (^^Q, ctx)[0]> (); // function template
> +  bar <253, members_of (^^NS2::Q, ctx)[0]> (); // function template
>     bar <260, ^^TVar> (); // variable template
>     bar <261, ^^NS2::TVar> (); // variable template
>     bar <270, ^^TAlias> (); // alias template
> @@ -239,6 +249,8 @@ baz (int x)
>   // { dg-final { scan-assembler "_Z3barILi241ELDmct3NS24TClsEEvv" } }
>   // { dg-final { scan-assembler "_Z3barILi250ELDmft3TFnEEvv" } }
>   // { dg-final { scan-assembler "_Z3barILi251ELDmft3NS23TFnEEvv" } }
> +// { dg-final { scan-assembler "_Z3barILi252ELDmft1QcvT_EEvv" } }
> +// { dg-final { scan-assembler "_Z3barILi253ELDmft3NS21QcviEEvv" } }
>   // { dg-final { scan-assembler "_Z3barILi260ELDmvt4TVarEEvv" } }
>   // { dg-final { scan-assembler "_Z3barILi261ELDmvt3NS24TVarEEvv" } }
>   // { dg-final { scan-assembler "_Z3barILi270ELDmat6TAliasEEvv" } }
> 
> 
> 	Jakub
>