debug: Improve debug info of c++14 deduced return type [PR94459]

Message ID 20200403224713.GK2212@tucnak
State New
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Series
  • debug: Improve debug info of c++14 deduced return type [PR94459]
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Commit Message

Jason Merrill via Gcc-patches April 3, 2020, 10:47 p.m.
Hi!

On the following testcase, in gdb ptype S<long>::m1 prints long as return
type, but all the other methods show void instead.
PR53756 added code to add_type_attribute if the return type is
auto/decltype(auto), but we actually should look through references,
pointers and qualifiers.
Haven't included there DW_TAG_atomic_type, because I think at least ATM
one can't use that in C++.  Not sure about DW_TAG_array_type or what else
could be deduced.

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

2020-04-04  Domani Hannes  <ssbssa@yahoo.de>
	    Jakub Jelinek  <jakub@redhat.com>

	PR debug/94459
	* dwarf2out.c (gen_subprogram_die): Look through references, pointers
	and qualifiers when checking if in-class DIE had an 'auto' or
	'decltype(auto)' return type to emit type again on definition.

	* g++.dg/debug/pr94459.C: New test.


	Jakub

Comments

Jason Merrill via Gcc-patches April 3, 2020, 10:58 p.m. | #1
Am Samstag, 4. April 2020, 00:47:27 MESZ hat Jakub Jelinek via Gcc-patches <gcc-patches@gcc.gnu.org> Folgendes geschrieben:

> Hi!

>

> On the following testcase, in gdb ptype S<long>::m1 prints long as return

> type, but all the other methods show void instead.

> PR53756 added code to add_type_attribute if the return type is

> auto/decltype(auto), but we actually should look through references,

> pointers and qualifiers.

> Haven't included there DW_TAG_atomic_type, because I think at least ATM

> one can't use that in C++.  Not sure about DW_TAG_array_type or what else

> could be deduced.

>

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

>

> 2020-04-04  Domani Hannes  <ssbssa@yahoo.de>

>         Jakub Jelinek  <jakub@redhat.com>


Minor hiccup from my side, my name should be written as Hannes Domani.

I think when I registered the bugzilla account, I wasn't aware yet that
it should be family name last, I've fixed that now.


Hannes
Jason Merrill via Gcc-patches April 4, 2020, 4:08 a.m. | #2
On 4/3/20 6:47 PM, Jakub Jelinek wrote:
> Hi!

> 

> On the following testcase, in gdb ptype S<long>::m1 prints long as return

> type, but all the other methods show void instead.

> PR53756 added code to add_type_attribute if the return type is

> auto/decltype(auto), but we actually should look through references,

> pointers and qualifiers.

> Haven't included there DW_TAG_atomic_type, because I think at least ATM

> one can't use that in C++.  Not sure about DW_TAG_array_type or what else

> could be deduced.


http://eel.is/c++draft/dcl.spec.auto#3 says it has to appear as a 
decl-specifier.

http://eel.is/c++draft/temp.deduct.type#8 lists the forms where a 
template argument can be deduced.

Looks like you are missing arrays, pointers to members, and function 
return types.

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

> 

> 2020-04-04  Domani Hannes  <ssbssa@yahoo.de>

> 	    Jakub Jelinek  <jakub@redhat.com>

> 

> 	PR debug/94459

> 	* dwarf2out.c (gen_subprogram_die): Look through references, pointers

> 	and qualifiers when checking if in-class DIE had an 'auto' or

> 	'decltype(auto)' return type to emit type again on definition.

> 

> 	* g++.dg/debug/pr94459.C: New test.

> 

> --- gcc/dwarf2out.c.jj	2020-04-03 10:04:44.704972108 +0200

> +++ gcc/dwarf2out.c	2020-04-03 17:52:48.909483818 +0200

> @@ -22905,11 +22905,19 @@ gen_subprogram_die (tree decl, dw_die_re

>   		  != (unsigned) s.column))

>   	    add_AT_unsigned (subr_die, DW_AT_decl_column, s.column);

>   

> -	  /* If the prototype had an 'auto' or 'decltype(auto)' return type,

> +	  /* If the prototype had a cv 'auto' or 'decltype(auto)' return type,

>   	     emit the real type on the definition die.  */

>   	  if (is_cxx () && debug_info_level > DINFO_LEVEL_TERSE)

>   	    {

>   	      dw_die_ref die = get_AT_ref (old_die, DW_AT_type);

> +	      while (die

> +		     && (die->die_tag == DW_TAG_reference_type

> +			 || die->die_tag == DW_TAG_rvalue_reference_type

> +			 || die->die_tag == DW_TAG_pointer_type

> +			 || die->die_tag == DW_TAG_const_type

> +			 || die->die_tag == DW_TAG_volatile_type

> +			 || die->die_tag == DW_TAG_restrict_type))

> +		die = get_AT_ref (die, DW_AT_type);

>   	      if (die == auto_die || die == decltype_auto_die)

>   		add_type_attribute (subr_die, TREE_TYPE (TREE_TYPE (decl)),

>   				    TYPE_UNQUALIFIED, false, context_die);

> --- gcc/testsuite/g++.dg/debug/pr94459.C.jj	2020-04-03 18:06:28.234725520 +0200

> +++ gcc/testsuite/g++.dg/debug/pr94459.C	2020-04-03 18:05:59.287104932 +0200

> @@ -0,0 +1,49 @@

> +// PR debug/94459

> +// { dg-do compile { target c++11 } }

> +// { dg-options "-g -dA" }

> +

> +template <typename T>

> +struct S

> +{

> +  T v;

> +  S () : v (0) {}

> +  auto m1 () { return v; }

> +  auto &m2 () { return v; }

> +  auto &&m3 () { return (T&&)v; }

> +  const auto m4 () { return v; }

> +  const auto &m5 () { return v; }

> +  const auto &&m6 () { return (T&&)v; }

> +  volatile auto m7 () { return v; }

> +  volatile auto &m8 () { return v; }

> +  volatile auto &&m9 () { return (T&&)v; }

> +  volatile const auto m10 () { return v; }

> +  volatile const auto &m11 () { return v; }

> +  volatile const auto &&m12 () { return (T&&)v; }

> +  const volatile auto m13 () { return v; }

> +  const volatile auto &m14 () { return v; }

> +  const volatile auto &&m15 () { return (T&&)v; }

> +#ifndef __STRICT_ANSI__

> +  __restrict const volatile auto &&m16 () { return (T&&)v; }

> +  const __restrict auto &m17 () { return v; }

> +#endif

> +};

> +

> +S<long> s, u, v;

> +

> +long

> +foo ()

> +{

> +  return s.m1 () + s.m2 () + s.m3 () + s.m4 () + s.m5 ()

> +	 + s.m6 () + s.m7 () + s.m8 () + s.m9 () + s.m10 ()

> +	 + s.m11 () + s.m12 () + s.m13 () + s.m14 () + s.m15 ()

> +#ifndef __STRICT_ANSI__

> +	 + u.m16 () + v.m17 ()

> +#endif

> +	 + 0;

> +}

> +

> +int

> +main ()

> +{

> +  return foo ();

> +}

> 

> 	Jakub

>

Patch

--- gcc/dwarf2out.c.jj	2020-04-03 10:04:44.704972108 +0200
+++ gcc/dwarf2out.c	2020-04-03 17:52:48.909483818 +0200
@@ -22905,11 +22905,19 @@  gen_subprogram_die (tree decl, dw_die_re
 		  != (unsigned) s.column))
 	    add_AT_unsigned (subr_die, DW_AT_decl_column, s.column);
 
-	  /* If the prototype had an 'auto' or 'decltype(auto)' return type,
+	  /* If the prototype had a cv 'auto' or 'decltype(auto)' return type,
 	     emit the real type on the definition die.  */
 	  if (is_cxx () && debug_info_level > DINFO_LEVEL_TERSE)
 	    {
 	      dw_die_ref die = get_AT_ref (old_die, DW_AT_type);
+	      while (die
+		     && (die->die_tag == DW_TAG_reference_type
+			 || die->die_tag == DW_TAG_rvalue_reference_type
+			 || die->die_tag == DW_TAG_pointer_type
+			 || die->die_tag == DW_TAG_const_type
+			 || die->die_tag == DW_TAG_volatile_type
+			 || die->die_tag == DW_TAG_restrict_type))
+		die = get_AT_ref (die, DW_AT_type);
 	      if (die == auto_die || die == decltype_auto_die)
 		add_type_attribute (subr_die, TREE_TYPE (TREE_TYPE (decl)),
 				    TYPE_UNQUALIFIED, false, context_die);
--- gcc/testsuite/g++.dg/debug/pr94459.C.jj	2020-04-03 18:06:28.234725520 +0200
+++ gcc/testsuite/g++.dg/debug/pr94459.C	2020-04-03 18:05:59.287104932 +0200
@@ -0,0 +1,49 @@ 
+// PR debug/94459
+// { dg-do compile { target c++11 } }
+// { dg-options "-g -dA" }
+
+template <typename T>
+struct S
+{
+  T v;
+  S () : v (0) {}
+  auto m1 () { return v; }
+  auto &m2 () { return v; }
+  auto &&m3 () { return (T&&)v; }
+  const auto m4 () { return v; }
+  const auto &m5 () { return v; }
+  const auto &&m6 () { return (T&&)v; }
+  volatile auto m7 () { return v; }
+  volatile auto &m8 () { return v; }
+  volatile auto &&m9 () { return (T&&)v; }
+  volatile const auto m10 () { return v; }
+  volatile const auto &m11 () { return v; }
+  volatile const auto &&m12 () { return (T&&)v; }
+  const volatile auto m13 () { return v; }
+  const volatile auto &m14 () { return v; }
+  const volatile auto &&m15 () { return (T&&)v; }
+#ifndef __STRICT_ANSI__
+  __restrict const volatile auto &&m16 () { return (T&&)v; }
+  const __restrict auto &m17 () { return v; }
+#endif
+};
+
+S<long> s, u, v;
+
+long
+foo ()
+{
+  return s.m1 () + s.m2 () + s.m3 () + s.m4 () + s.m5 ()
+	 + s.m6 () + s.m7 () + s.m8 () + s.m9 () + s.m10 ()
+	 + s.m11 () + s.m12 () + s.m13 () + s.m14 () + s.m15 ()
+#ifndef __STRICT_ANSI__
+	 + u.m16 () + v.m17 ()
+#endif
+	 + 0;
+}
+
+int
+main ()
+{
+  return foo ();
+}