[gdb/tdep] Fix inferior call return of small char array for ppc64 v1 abi

In ppc64_sysv_abi_return_value I came across this if clause:
...
   /* Small character arrays are returned, right justified, in r3.  */
  if (valtype->code () == TYPE_CODE_ARRAY
      && !valtype->is_vector ()
      && valtype->length () <= 8
      && valtype->target_type ()->code () == TYPE_CODE_INT
      && valtype->target_type ()->length () == 1)
...

I decided to write a test-case to try and trigger this.

AFAIU, in C/C++, we're not allowed to return an array, so I wrote an Ada
test-case instead, with a function returning this type:
...
  type T is new String (1 .. 4);
...

After doing so I realized that the clause above is not triggering because
valtype->target_type ()->code () == TYPE_CODE_CHAR.  Fix this by allowing
both TYPE_CODE_INT and TYPE_CODE_CHAR.

Then I realized that the specific "small character array" handling comes from
the v1 abi.  Add a check for this as well.

Tested on ppc64le-linux, with v2 abi.

Approved-By: Simon Marchi <simon.marchi@efficios.com>

5 files changed, 107 insertions, 2 deletions

diff --git a/gdb/ppc-sysv-tdep.c b/gdb/ppc-sysv-tdep.c
index cae5aa6..f872f73 100644
--- a/gdb/ppc-sysv-tdep.c
+++ b/gdb/ppc-sysv-tdep.c
@@ -2060,10 +2060,12 @@ ppc64_sysv_abi_return_value (struct gdbarch *gdbarch, struct value *function,
     }
 
   /* Small character arrays are returned, right justified, in r3.  */
-  if (valtype->code () == TYPE_CODE_ARRAY
+  if (tdep->elf_abi == POWERPC_ELF_V1
+      && valtype->code () == TYPE_CODE_ARRAY
       && !valtype->is_vector ()
       && valtype->length () <= 8
-      && valtype->target_type ()->code () == TYPE_CODE_INT
+      && (valtype->target_type ()->code () == TYPE_CODE_INT
+	  || valtype->target_type ()->code () == TYPE_CODE_CHAR)
       && valtype->target_type ()->length () == 1)
     {
       int regnum = tdep->ppc_gp0_regnum + 3;
diff --git a/gdb/testsuite/gdb.ada/return-small-char-array.exp b/gdb/testsuite/gdb.ada/return-small-char-array.exp
new file mode 100644
index 0000000..75c781e
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/return-small-char-array.exp
@@ -0,0 +1,40 @@
+# Copyright 2025 Free Software Foundation, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+load_lib "ada.exp"
+
+require allow_ada_tests
+
+standard_ada_testfile proc
+
+if { [gdb_compile_ada $srcfile $binfile executable debug] != "" } {
+  return -1
+}
+
+clean_restart $testfile
+
+set bp_location [gdb_get_line_number "STOP" $testdir/proc.adb]
+runto "proc.adb:$bp_location"
+
+gdb_test "print Value.Name(My_Value)" \
+    { = "abcd"}
+
+# Step into the function.
+gdb_test "step 2" \
+    "return Of_Value;"
+
+# and finish.
+gdb_test "finish" \
+    { = "abcd"}
diff --git a/gdb/testsuite/gdb.ada/return-small-char-array/proc.adb b/gdb/testsuite/gdb.ada/return-small-char-array/proc.adb
new file mode 100644
index 0000000..b18d9fe
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/return-small-char-array/proc.adb
@@ -0,0 +1,22 @@
+--  Copyright 2025 Free Software Foundation, Inc.
+--
+--  This program is free software; you can redistribute it and/or modify
+--  it under the terms of the GNU General Public License as published by
+--  the Free Software Foundation; either version 3 of the License, or
+--  (at your option) any later version.
+--
+--  This program is distributed in the hope that it will be useful,
+--  but WITHOUT ANY WARRANTY; without even the implied warranty of
+--  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+--  GNU General Public License for more details.
+--
+--  You should have received a copy of the GNU General Public License
+--  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+with Value;
+procedure Proc is
+  My_Value : Value.T := "abcd";
+begin
+  null; -- STOP
+  My_Value := Value.Name(My_Value);
+end;
diff --git a/gdb/testsuite/gdb.ada/return-small-char-array/value.adb b/gdb/testsuite/gdb.ada/return-small-char-array/value.adb
new file mode 100644
index 0000000..2dd9faa
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/return-small-char-array/value.adb
@@ -0,0 +1,21 @@
+--  Copyright 2025 Free Software Foundation, Inc.
+--
+--  This program is free software; you can redistribute it and/or modify
+--  it under the terms of the GNU General Public License as published by
+--  the Free Software Foundation; either version 3 of the License, or
+--  (at your option) any later version.
+--
+--  This program is distributed in the hope that it will be useful,
+--  but WITHOUT ANY WARRANTY; without even the implied warranty of
+--  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+--  GNU General Public License for more details.
+--
+--  You should have received a copy of the GNU General Public License
+--  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package body Value is
+  function Name (Of_Value : T) return T is
+  begin
+    return Of_Value;
+  end Name;
+end Value;
diff --git a/gdb/testsuite/gdb.ada/return-small-char-array/value.ads b/gdb/testsuite/gdb.ada/return-small-char-array/value.ads
new file mode 100644
index 0000000..16b171e
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/return-small-char-array/value.ads
@@ -0,0 +1,20 @@
+--  Copyright 2025 Free Software Foundation, Inc.
+--
+--  This program is free software; you can redistribute it and/or modify
+--  it under the terms of the GNU General Public License as published by
+--  the Free Software Foundation; either version 3 of the License, or
+--  (at your option) any later version.
+--
+--  This program is distributed in the hope that it will be useful,
+--  but WITHOUT ANY WARRANTY; without even the implied warranty of
+--  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+--  GNU General Public License for more details.
+--
+--  You should have received a copy of the GNU General Public License
+--  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package Value is
+  type T is new String (1 .. 4);
+
+  function Name (Of_Value : T) return T;
+end;