[PATCH] c++: Remove superflous assert [PR104403]

[PATCH] c++: Remove superflous assert [PR104403]

[Jakub Jelinek]

Hi!

I've added the assert because start_decl diagnoses such vars for C++20 and
earlier:
  if (current_function_decl && VAR_P (decl)
      && DECL_DECLARED_CONSTEXPR_P (current_function_decl)
      && cxx_dialect < cxx23)
but as can be seen, we cam trigger the assert in older standards e.g. during
non-manifestly constant evaluation.  Rather than refining the assert that
DECL_EXPRs for such vars don't appear for C++20 and older if they are inside
of functions declared constexpr this patch just removes the assert, the
code rejects encountering those vars in constant expressions anyway.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2022-02-08  Jakub Jelinek  <jakub@redhat.com>

	PR c++/104403
	* constexpr.cc (cxx_eval_constant_expression): Don't assert DECL_EXPRs
	of TREE_STATIC vars may only appear in -std=c++23.

	* g++.dg/cpp0x/lambda/lambda-104403.C: New test.

--- gcc/cp/constexpr.cc.jj	2022-02-06 11:16:22.353814431 +0100
+++ gcc/cp/constexpr.cc	2022-02-07 11:38:59.131165171 +0100
@@ -6652,7 +6652,6 @@ cxx_eval_constant_expression (const cons
 	    /* Allow __FUNCTION__ etc.  */
 	    && !DECL_ARTIFICIAL (r))
 	  {
-	    gcc_assert (cxx_dialect >= cxx23);
 	    if (!ctx->quiet)
 	      {
 		if (CP_DECL_THREAD_LOCAL_P (r))
--- gcc/testsuite/g++.dg/cpp0x/lambda/lambda-104403.C.jj	2022-02-07 11:40:32.760847269 +0100
+++ gcc/testsuite/g++.dg/cpp0x/lambda/lambda-104403.C	2022-02-07 11:40:06.109223079 +0100
@@ -0,0 +1,8 @@
+// PR c++/104403
+// { dg-do compile { target c++11 } }
+
+int
+main ()
+{
+  []{ switch (0) { case 0: static int value; return &value; } };
+}

	Jakub

Re: [PATCH] c++: Remove superflous assert [PR104403]

[Jason Merrill]

On 2/8/22 03:16, Jakub Jelinek wrote:
> Hi!
> 
> I've added the assert because start_decl diagnoses such vars for C++20 and
> earlier:
>    if (current_function_decl && VAR_P (decl)
>        && DECL_DECLARED_CONSTEXPR_P (current_function_decl)
>        && cxx_dialect < cxx23)
> but as can be seen, we cam trigger the assert in older standards e.g. during
> non-manifestly constant evaluation.  Rather than refining the assert that
> DECL_EXPRs for such vars don't appear for C++20 and older if they are inside
> of functions declared constexpr this patch just removes the assert, the
> code rejects encountering those vars in constant expressions anyway.
> 
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

OK.

> 2022-02-08  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR c++/104403
> 	* constexpr.cc (cxx_eval_constant_expression): Don't assert DECL_EXPRs
> 	of TREE_STATIC vars may only appear in -std=c++23.
> 
> 	* g++.dg/cpp0x/lambda/lambda-104403.C: New test.
> 
> --- gcc/cp/constexpr.cc.jj	2022-02-06 11:16:22.353814431 +0100
> +++ gcc/cp/constexpr.cc	2022-02-07 11:38:59.131165171 +0100
> @@ -6652,7 +6652,6 @@ cxx_eval_constant_expression (const cons
>   	    /* Allow __FUNCTION__ etc.  */
>   	    && !DECL_ARTIFICIAL (r))
>   	  {
> -	    gcc_assert (cxx_dialect >= cxx23);
>   	    if (!ctx->quiet)
>   	      {
>   		if (CP_DECL_THREAD_LOCAL_P (r))
> --- gcc/testsuite/g++.dg/cpp0x/lambda/lambda-104403.C.jj	2022-02-07 11:40:32.760847269 +0100
> +++ gcc/testsuite/g++.dg/cpp0x/lambda/lambda-104403.C	2022-02-07 11:40:06.109223079 +0100
> @@ -0,0 +1,8 @@
> +// PR c++/104403
> +// { dg-do compile { target c++11 } }
> +
> +int
> +main ()
> +{
> +  []{ switch (0) { case 0: static int value; return &value; } };
> +}
> 
> 	Jakub
>