gdb/python: add Type.is_signed property

Add a new read-only property, Type.is_signed, which is True for signed
types, and False otherwise.

This property should only be read on types for which Type.is_scalar is
true, attempting to read this property for non-scalar types will raise
a ValueError.

I chose 'is_signed' rather than 'is_unsigned' in order to match the
existing Architecture.integer_type method, which takes a 'signed'
parameter.  As far as I could find, that was the only existing
signed/unsigned selector in the Python API, so it seemed reasonable to
stay consistent.

gdb/NEWS

@@ -235,6 +235,11 @@ GNU/Linux/LoongArch    loongarch*-*-linux*
   ** New read-only attribute gdb.Type.is_scalar, which is True for
      scalar types, and False for all other types.
 
+  ** New read-only attribute gdb.Type.is_signed.  This attribute
+     should only be read when Type.is_scalar is True, and will be True
+     for signed types, and False for all other types.  Attempting to
+     read this attribute for non-scalar types will raise a ValueError.
+
 * New features in the GDB remote stub, GDBserver
 
   ** GDBserver is now supported on OpenRISC GNU/Linux.

gdb/doc/python.texi

@@ -1269,6 +1269,16 @@ this property is @code{False}.  Examples of non-scalar types include
 structures, unions, and classes.
 @end defvar
 
+@defvar Type.is_signed
+For scalar types (those for which @code{Type.is_scalar} is
+@code{True}), this property is @code{True} if the type is signed,
+otherwise this property is @code{False}.
+
+Attempting to read this property for a non-scalar type (a type for
+which @code{Type.is_scalar} is @code{False}), will raise a
+@code{ValueError}.
+@end defvar
+
 The following methods are provided:
 
 @defun Type.fields ()

gdb/python/py-type.c

@@ -446,6 +446,27 @@ typy_is_scalar (PyObject *self, void *closure)
     Py_RETURN_FALSE;
 }
 
+/* Return true if this type is signed.  Raises a ValueError if this type
+   is not a scalar type.  */
+
+static PyObject *
+typy_is_signed (PyObject *self, void *closure)
+{
+  struct type *type = ((type_object *) self)->type;
+
+  if (!is_scalar_type (type))
+    {
+      PyErr_SetString (PyExc_ValueError,
+		       _("Type must be a scalar type"));
+      return nullptr;
+    }
+
+  if (type->is_unsigned ())
+    Py_RETURN_FALSE;
+  else
+    Py_RETURN_TRUE;
+}
+
 /* Return the type, stripped of typedefs. */
 static PyObject *
 typy_strip_typedefs (PyObject *self, PyObject *args)
@@ -1502,6 +1523,8 @@ static gdb_PyGetSetDef type_object_getset[] =
     "The objfile this type was defined in, or None.", NULL },
   { "is_scalar", typy_is_scalar, nullptr,
     "Is this a scalar type?", nullptr },
+  { "is_signed", typy_is_signed, nullptr,
+    "Is this an signed type?", nullptr },
   { NULL }
 };
 

gdb/testsuite/gdb.python/py-arch.exp

@@ -64,12 +64,25 @@ if { ![is_address_zero_readable] } {
 }
 
 foreach size {0 1 2 3 4 8 16} {
-    foreach sign {"" ", True" ", False" ", None" ", \"blah\""} {
+    foreach sign_data {{"" True} \
+			   {", True" True} \
+			   {", False" False} \
+			   {", None" False} \
+			   {", \"blah\"" True}} {
+	set sign [lindex $sign_data 0]
+	# GDB's 0 bit type is always signed.
+	if { $size == 0 } {
+	    set sign_result True
+	} else {
+	    set sign_result [lindex $sign_data 1]
+	}
 	set fullsize [expr 8 * $size]
 	gdb_test_no_output "python t = arch.integer_type($fullsize$sign)" \
 	    "get integer type for $size$sign"
 	gdb_test "python print(t.sizeof)" "$size" \
 	    "print size of integer type for $size$sign"
+	gdb_test "python print(t.is_signed == ${sign_result})" "True" \
+	    "check signedness of type for $size$sign"
     }
 }
 

gdb/testsuite/gdb.python/py-type.exp

@@ -270,6 +270,32 @@ proc test_template {} {
     gdb_test "python print (ttype.template_argument(2))" "&C::c"
 }
 
+# Check the is_signed property of some types.
+proc test_is_signed {lang} {
+    if {$lang == "c++"} {
+	gdb_test "python print(gdb.parse_and_eval ('c').type.is_signed)"  \
+	"ValueError: Type must be a scalar type.*"
+	gdb_test "python print(gdb.parse_and_eval ('&c').type.is_signed == False)" "True"
+    }
+
+    gdb_test "python print(gdb.parse_and_eval('global_unsigned_char').type.is_signed == False)" "True"
+    gdb_test "python print(gdb.parse_and_eval('global_char').type.is_signed)" "True|False"
+    gdb_test "python print(gdb.parse_and_eval('global_signed_char').type.is_signed == True)" "True"
+
+    gdb_test "python print(gdb.parse_and_eval ('ss.x').type.is_signed == True)" "True"
+    gdb_test "python print(gdb.parse_and_eval ('ss').type.is_signed)" \
+	"ValueError: Type must be a scalar type.*"
+    gdb_test "python print(gdb.parse_and_eval ('uu').type.is_signed)"  \
+	"ValueError: Type must be a scalar type.*"
+    gdb_test "python print(gdb.parse_and_eval ('uu.i').type.is_signed == True)" "True"
+    gdb_test "python print(gdb.parse_and_eval ('uu.f').type.is_signed == True)" "True"
+    gdb_test "python print(gdb.parse_and_eval ('uu.a').type.is_signed)"  \
+	"ValueError: Type must be a scalar type.*"
+
+    gdb_test "python print(gdb.parse_and_eval ('&ss.x').type.is_signed == False)" "True"
+    gdb_test "python print(gdb.parse_and_eval ('&uu').type.is_signed == False)" "True"
+}
+
 # Test the gdb.Type.is_scalar property.
 proc test_is_scalar { lang } {
     if {$lang == "c++"} {
@@ -320,6 +346,7 @@ if { [build_inferior "${binfile}" "c"] == 0 } {
       test_fields "c"
       test_enums
       test_is_scalar "c"
+      test_is_signed "c"
   }
 }
 
@@ -334,5 +361,6 @@ if { [build_inferior "${binfile}-cxx" "c++"] == 0 } {
       test_template
       test_enums
       test_is_scalar "c++"
+      test_is_signed "c++"
   }
 }