[PATCH v5 2/2] gdb: Keep original IFUNC return type when target type is unknown

When find_function_addr resolves a GNU IFUNC, it tries to replace the
original function type with the resolved target type, or with the type
returned by the resolver.  If neither source provides a useful return
type, keep the return type from the original function value.

This matters for internal inferior calls such as
find_function_in_inferior ("malloc"), where GDB creates a synthetic
function type with a known fallback return type.

Remove the guard from the IFUNC inferior-call test so the no-debug
resolver/no-debug target variants are tested too.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=34330
---
 gdb/infcall.c                        | 12 ++++++++++--
 gdb/testsuite/gdb.base/gnu-ifunc.exp |  7 -------
 2 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/gdb/infcall.c b/gdb/infcall.c
index e6b24ff5310..4c40f6cb06e 100644
--- a/gdb/infcall.c
+++ b/gdb/infcall.c
@@ -395,6 +395,9 @@ find_function_addr (struct value *function,
 	     FUNCTION_TYPE have been asked for.  */
 	  if (retval_type != NULL || function_type != NULL)
 	    {
+	      /* Default to original function type's return type.  Target type
+		 replaces this only if it provides a usable return type.  */
+	      value_type = ftype->target_type ();
 	      type *target_ftype = find_function_type (funaddr);
 	      /* If we don't have debug info for the target function,
 		 see if we can instead extract the target function's
@@ -403,8 +406,13 @@ find_function_addr (struct value *function,
 		target_ftype = find_gnu_ifunc_target_type (resolver_addr);
 	      if (target_ftype != NULL)
 		{
-		  value_type = check_typedef (target_ftype)->target_type ();
-		  ftype = target_ftype;
+		  type *target_value_type
+		    = check_typedef (target_ftype)->target_type ();
+		  if (target_value_type != nullptr)
+		    {
+		      value_type = target_value_type;
+		      ftype = target_ftype;
+		    }
 		}
 	    }
 	}
diff --git a/gdb/testsuite/gdb.base/gnu-ifunc.exp b/gdb/testsuite/gdb.base/gnu-ifunc.exp
index d146a197776..ab992bc2363 100644
--- a/gdb/testsuite/gdb.base/gnu-ifunc.exp
+++ b/gdb/testsuite/gdb.base/gnu-ifunc.exp
@@ -448,13 +448,6 @@ proc_with_prefix test_inferior_call {resolver_attr resolver_debug final_debug} {
        return
     }
 
-    # Without debug info for both the resolver and the resolved target,
-    # find_function_addr currently loses the synthetic return type after
-    # resolving the IFUNC.
-    if {!$resolver_debug && !$final_debug} {
-	unsupported "internal call resolves IFUNC malloc"
-	return
-    }
     gdb_test "print (get_string (\"hello-ifunc\"), str_in_arena ())" \
 	" = 1" \
 	"internal call resolves IFUNC malloc"
-- 
2.43.0