backends: Handle DW_TAG_unspecified_type in dwarf_peeled_die_type

binutils 2.40 introduces DW_TAG_unspecified_type for assembly
functions with an unknown return type. This breaks the
run-funcretval.sh testcase because dwfl_module_return_value_location
returns an error for such functions because it cannot determine the
return value location. Fix that by treating DW_TAG_unspecified_type
as if the DIE doesn't have a DW_AT_type.

Also update the testcase to explicitly checking for
DW_TAG_unspecified_type and printing "returns unspecified type".

https://sourceware.org/bugzilla/show_bug.cgi?id=30047

Signed-off-by: Mark Wielaard <mark@klomp.org>

5 files changed, 40 insertions, 3 deletions

diff --git a/NEWS b/NEWS
index 71534b8c..80faca39 100644
--- a/NEWS
+++ b/NEWS
@@ -1,3 +1,8 @@
+Version 0.189
+
+libdwfl: dwfl_module_return_value_location now returns 0 (no return type)
+         for DIEs that point to a DW_TAG_unspecified_type.
+
 Version 0.188
 
 readelf: Add -D, --use-dynamic option.
diff --git a/backends/ChangeLog b/backends/ChangeLog
index 40ec7c0c..81f08314 100644
--- a/backends/ChangeLog
+++ b/backends/ChangeLog
@@ -1,3 +1,8 @@
+2023-02-07  Mark Wielaard  <mark@klomp.org>
+
+	* libebl_CPU.h (dwarf_peeled_die_type): Explicitly handle
+	DW_TAG_unspecified_type as if there was no DW_AT_type.
+
 2023-01-19  Mark Wielaard  <mark@klomp.org>
 
 	* sparc_reloc.def (NONE): Add EXEC and DYN.
diff --git a/backends/libebl_CPU.h b/backends/libebl_CPU.h
index 2abad76f..3b2cc3e4 100644
--- a/backends/libebl_CPU.h
+++ b/backends/libebl_CPU.h
@@ -1,5 +1,6 @@
 /* Common interface for libebl modules.
    Copyright (C) 2000, 2001, 2002, 2003, 2005, 2013, 2014 Red Hat, Inc.
+   Copyright (C) 2023 Mark J. Wielaard <mark@klomp.org>
    This file is part of elfutils.
 
    This file is free software; you can redistribute it and/or modify
@@ -53,7 +54,9 @@ extern bool (*generic_debugscn_p) (const char *) attribute_hidden;
      dwarf_tag (_die); })
 
 /* Get a type die corresponding to DIE.  Peel CV qualifiers off
-   it.  */
+   it.  Returns zero if the DIE doesn't have a type, or the type
+   is DW_TAG_unspecified_type.  Returns -1 on error.  Otherwise
+   returns the result tag DW_AT value.  */
 static inline int
 dwarf_peeled_die_type (Dwarf_Die *die, Dwarf_Die *result)
 {
@@ -69,7 +72,14 @@ dwarf_peeled_die_type (Dwarf_Die *die, Dwarf_Die *result)
   if (dwarf_peel_type (result, result) != 0)
     return -1;
 
-  return DWARF_TAG_OR_RETURN (result);
+  if (result == NULL)
+    return -1;
+
+  int tag = dwarf_tag (result);
+  if (tag == DW_TAG_unspecified_type)
+    return 0; /* Treat an unspecified type as if there was no type.  */
+
+  return tag;
 }
 
 static inline bool
diff --git a/tests/ChangeLog b/tests/ChangeLog
index 974a3a4f..89f1a991 100644
--- a/tests/ChangeLog
+++ b/tests/ChangeLog
@@ -1,3 +1,8 @@
+2023-02-07  Mark Wielaard  <mark@klomp.org>
+
+	* tests/funcretval.c (handle_function): Check for
+	DW_TAG_unspecified_type.
+
 2023-02-03  Mark Wielaard  <mark@klomp.org>
 
 	* run-addr2line-C-test.sh: Check ELFUTILS_DISABLE_DEMANGLE.
diff --git a/tests/funcretval.c b/tests/funcretval.c
index 16cd1a44..41198ab7 100644
--- a/tests/funcretval.c
+++ b/tests/funcretval.c
@@ -1,5 +1,6 @@
 /* Test program for dwfl_module_return_value_location.
    Copyright (C) 2005 Red Hat, Inc.
+   Copyright (C) 2023 Mark J. Wielaard <mark@klomp.org>
    This file is part of elfutils.
 
    This file is free software; you can redistribute it and/or modify
@@ -67,7 +68,18 @@ handle_function (Dwarf_Die *funcdie, void *arg)
     error (EXIT_FAILURE, 0, "dwfl_module_return_value_location: %s",
 	   dwfl_errmsg (-1));
   else if (nlocops == 0)
-    puts ("returns no value");
+    {
+      // Check if this is the special unspecified type
+      // https://sourceware.org/bugzilla/show_bug.cgi?id=30047
+      Dwarf_Die die_mem, *typedie = &die_mem;
+      Dwarf_Attribute attr_mem, *attr;
+      attr = dwarf_attr_integrate (funcdie, DW_AT_type, &attr_mem);
+      if (dwarf_formref_die (attr, typedie) != NULL
+	  && dwarf_tag (typedie) == DW_TAG_unspecified_type)
+	puts ("returns unspecified type");
+      else
+	puts ("returns no value");
+    }
   else
     {
       printf ("return value location:");