[PATCHv6 4/4] gdb/python: extend gdb.write to support styled output

Andrew Burgess
2025-07-07T14:46:44Z

It is already possible to produce styled output from Python by
converting the gdb.Style to its escape code sequence, and writing that
to the output stream.

But this commit adds an alternative option to the mix by extending the
existing gdb.write() function to accept a 'style' argument. The value
of this argument can be 'None' to indicate no style change should be
performed, this is the default, and matches the existing behaviour.

Or the new 'style' argument can be a gdb.Style object, in which case
the specified style is applied only for the string passed to
gdb.write, after which the default style is re-applied.

Using gdb.write with a style object more closely matches how GDB
handles styling internally, and has the benefit that the user doesn't
need to remember to restore the default style when they are done.
---
gdb/NEWS | 3 ++
gdb/doc/python.texi | 9 +++-
gdb/python/py-style.c | 27 ++++++++++
gdb/python/python-internal.h | 15 ++++++
gdb/python/python.c | 30 ++++++++++--
.../gdb.python/py-color-pagination.exp | 49 +++++++++++++++++++
.../gdb.python/py-color-pagination.py | 16 ++++++
gdb/testsuite/gdb.python/py-style.exp | 29 +++++++++++
8 files changed, 172 insertions(+), 6 deletions(-)

diff --git a/gdb/NEWS b/gdb/NEWS
index 6ae6710e877..6a324706a1f 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -148,6 +148,9 @@ info threads [-gid] [-stopped] [-running] [ID]...
Use gdb.StyleParameterSet(NAME) to create 'set style NAME ...'
and 'show style NAME ...' parameters.

+ ** The gdb.write() function now takes an additional, optional,
+ 'style' argument, which can be used to style the output.
+
** The memory_source argument (the second argument) has been removed
from gdb.disassembler.builtin_disassemble. This argument was
never used by GDB, and was added by mistake. The unused argument
diff --git a/gdb/doc/python.texi b/gdb/doc/python.texi
index 486f0a8f750..55a79b6785d 100644
--- a/gdb/doc/python.texi
+++ b/gdb/doc/python.texi
@@ -452,7 +452,7 @@ Basic Python
historical compatibility.
@end defun

-@defun gdb.write (string @r{[}, stream@r{]})
+@defun gdb.write (string @r{[}, stream@r{]} @r{[}, style@r{]})
Print a string to @value{GDBN}'s paginated output stream. The
optional @var{stream} determines the stream to print to. The default
stream is @value{GDBN}'s standard output stream. Possible stream
@@ -475,6 +475,13 @@ Basic Python
@value{GDBN}'s log stream (@pxref{Logging Output}).
@end table

+The @var{style} should be a @code{gdb.Style} object (@pxref{Styles In
+Python}), or @code{None} (the default). If @var{style} is @code{None}
+then the current style for @var{stream} will be applied to @var{text}.
+If @var{style} is a @code{gdb.Style} object, then this style is
+applied to @var{text}, after which the default output style is
+restored.
+
Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
call this function and will automatically direct the output to the
relevant stream.
diff --git a/gdb/python/py-style.c b/gdb/python/py-style.c
index b3983af3a85..0e9af1fc4c4 100644
--- a/gdb/python/py-style.c
+++ b/gdb/python/py-style.c
@@ -353,6 +353,15 @@ stylepy_init (PyObject *self, PyObject *args, PyObject *kwargs)

\f

+/* See python-internal.h. */
+
+bool
+gdbpy_is_style (PyObject *obj)
+{
+ gdb_assert (obj != nullptr);
+ return PyObject_TypeCheck (obj, &style_object_type);
+}
+
/* Return the ui_file_style for STYLEPY. If the style cannot be found,
then return an empty optional, and set a Python error. */

@@ -369,6 +378,24 @@ stylepy_to_style (style_object *stylepy)
return style;
}

+/* See python-internal.h. */
+
+std::optional<ui_file_style>
+gdbpy_style_object_to_ui_file_style (PyObject *obj)
+{
+ gdb_assert (obj != nullptr);
+ if (!gdbpy_is_style (obj))
+ {
+ PyErr_Format
+ (PyExc_TypeError, _("argument must be a gdb.Style object, not %s."),
+ Py_TYPE (obj)->tp_name);
+ return {};
+ }
+
+ style_object *style_obj = (style_object *) obj;
+ return stylepy_to_style (style_obj);
+}
+
/* Implementation of gdb.Style.escape_sequence(). Return the escape
sequence to apply Style. If styling is turned off, then this returns
the empty string. Can raise an exception if a named style can no longer
diff --git a/gdb/python/python-internal.h b/gdb/python/python-internal.h
index 7f4237eecc2..28199691226 100644
--- a/gdb/python/python-internal.h
+++ b/gdb/python/python-internal.h
@@ -565,6 +565,21 @@ struct symtab_and_line *sal_object_to_symtab_and_line (PyObject *obj);
frame_info_ptr frame_object_to_frame_info (PyObject *frame_obj);
struct gdbarch *arch_object_to_gdbarch (PyObject *obj);

+/* Return true if OBJ is a gdb.Style object. OBJ must not be NULL. */
+
+extern bool gdbpy_is_style (PyObject *obj);
+
+/* Return the ui_file_style from OBJ, a gdb.Style object. OBJ must not be
+ NULL, but can be a non gdb.Style object, in which case a Python error is
+ set and an empty optional is returned.
+
+ It is also possible that OBJ is a gdb.Style object, but the underlying
+ style cannot be fetched for some reason. If this happens then a Python
+ error is set and an empty optional is returned. */
+
+extern std::optional<ui_file_style>
+ gdbpy_style_object_to_ui_file_style (PyObject *obj);
+
extern PyObject *gdbpy_execute_mi_command (PyObject *self, PyObject *args,
PyObject *kw);

diff --git a/gdb/python/python.c b/gdb/python/python.c
index 1af7896eb08..77d96da61c6 100644
--- a/gdb/python/python.c
+++ b/gdb/python/python.c
@@ -1561,12 +1561,22 @@ static PyObject *
gdbpy_write (PyObject *self, PyObject *args, PyObject *kw)
{
const char *arg;
- static const char *keywords[] = { "text", "stream", NULL };
+ static const char *keywords[] = { "text", "stream", "style", nullptr };
int stream_type = 0;
+ PyObject *style_obj = Py_None;

- if (!gdb_PyArg_ParseTupleAndKeywords (args, kw, "s|i", keywords, &arg,
- &stream_type))
- return NULL;
+ if (!gdb_PyArg_ParseTupleAndKeywords (args, kw, "s|iO", keywords, &arg,
+ &stream_type, &style_obj))
+ return nullptr;
+
+ if (style_obj != Py_None && !gdbpy_is_style (style_obj))
+ {
+ PyErr_Format
+ (PyExc_TypeError,
+ _("'style' argument must be gdb.Style or None, not %s."),
+ Py_TYPE (style_obj)->tp_name);
+ return nullptr;
+ }

try
{
@@ -1584,7 +1594,17 @@ gdbpy_write (PyObject *self, PyObject *args, PyObject *kw)
break;
}

- gdb_puts (arg, stream);
+ if (style_obj == Py_None)
+ gdb_puts (arg, stream);
+ else
+ {
+ std::optional<ui_file_style> style
+ = gdbpy_style_object_to_ui_file_style (style_obj);
+ if (!style.has_value ())
+ return nullptr;
+
+ fputs_styled (arg, style.value (), stream);
+ }
}
catch (const gdb_exception &except)
{
diff --git a/gdb/testsuite/gdb.python/py-color-pagination.exp b/gdb/testsuite/gdb.python/py-color-pagination.exp
index 7b3dc1859c1..0a2f01e6533 100644
--- a/gdb/testsuite/gdb.python/py-color-pagination.exp
+++ b/gdb/testsuite/gdb.python/py-color-pagination.exp
@@ -110,8 +110,57 @@ proc test_pagination { type mode } {
}
}

+# Run the command 'style-fill-v2' which fills the screen with output and
+# triggers the pagination prompt. Check that styling is applied correctly
+# to the output. This v2 command is exercising passing a style to
+# gdb.write() rather than passing the escape sequence for the style.
+proc test_pagination_v2 { } {
+ set saw_bad_color_handling false
+ set expected_restore_color ""
+ set last_color ""
+ gdb_test_multiple "style-fill-v2" "" {
+ -re "^style-fill-v2\r\n" {
+ exp_continue
+ }
+
+ -re "^((?:${::any_color}\033\\\[m)?)(${::any_color})$::str\033\\\[m" {
+ # After a continuation prompt GDB will restore the previous
+ # color, and then we immediately switch to a new color.
+ set restored_color $expect_out(1,string)
+ if { $restored_color ne ""
+ && $restored_color ne $expected_restore_color } {
+ set saw_bad_color_handling true
+ }
+ set last_color $expect_out(2,string)
+ exp_continue
+ }
+
+ -re "^$::pagination_prompt$" {
+ # After a pagination prompt we expect GDB to restore the last
+ # color, but this will then be disabled due to a styled
+ # gdb.write emitting a return to default style escape sequence.
+ set expected_restore_color "$last_color\033\[m"
+
+ # Send '\n' to view more output.
+ send_gdb "\n"
+ exp_continue
+ }
+
+ -re "^\r\n" {
+ # The matches the newline sent to the continuation prompt.
+ exp_continue
+ }
+
+ -re "^$::gdb_prompt $" {
+ gdb_assert { !$saw_bad_color_handling } $gdb_test_name
+ }
+ }
+}
+
foreach_with_prefix type { color style } {
foreach_with_prefix mode { write print } {
test_pagination $type $mode
}
}
+
+test_pagination_v2
diff --git a/gdb/testsuite/gdb.python/py-color-pagination.py b/gdb/testsuite/gdb.python/py-color-pagination.py
index f0252e5bf86..9cdc76cb0ce 100644
--- a/gdb/testsuite/gdb.python/py-color-pagination.py
+++ b/gdb/testsuite/gdb.python/py-color-pagination.py
@@ -62,5 +62,21 @@ class StyleTester(gdb.Command):
write(mode, "\n")

+class StyleTester2(gdb.Command):
+ def __init__(self):
+ super().__init__("style-fill-v2", gdb.COMMAND_USER)
+
+ def invoke(self, args, from_tty):
+ str = "<" + "-" * 78 + ">"
+ for i in range(0, 20):
+ for color_name in basic_colors:
+ c = gdb.Color(color_name)
+ s = gdb.Style(foreground=c)
+ gdb.write(str, style=s)
+
+ gdb.write("\n")
+
+
ColorTester()
StyleTester()
+StyleTester2()
diff --git a/gdb/testsuite/gdb.python/py-style.exp b/gdb/testsuite/gdb.python/py-style.exp
index 020d0e0319b..7f3b01333a1 100644
--- a/gdb/testsuite/gdb.python/py-style.exp
+++ b/gdb/testsuite/gdb.python/py-style.exp
@@ -340,3 +340,32 @@ gdb_test_no_output "python input_text = \"a totally different string that is als
gdb_test "python print(output_text)" \
"^this is a unique string that is unlikely to appear elsewhere 12345" \
"check the output_text is still valid"
+
+# Test gdb.write passing in a style. Define a helper function to
+# ensure all output is flushed before we return to the prompt.
+gdb_test_multiline "create function to call gdb.write then flush" \
+ "python" "" \
+ "def write_and_flush(*args, **kwargs):" "" \
+ " gdb.write(*args, **kwargs)" "" \
+ " gdb.write(\"\\n\")" "" \
+ " gdb.flush(gdb.STDOUT)" "" \
+ "end" ""
+
+gdb_test "python write_and_flush(\"some text\")" \
+ "^some text" "unstyled text, no style passed"
+
+gdb_test "python write_and_flush(\"some text\", style=None)" \
+ "^some text" "unstyled text, pass style as None"
+
+gdb_test "python write_and_flush(\"some text\", style=filename_style)" \
+ "^\033\\\[34;41;2;27msome text\033\\\[m" \
+ "styled output, pass style by keyword"
+
+gdb_test "python write_and_flush(\"some text\", gdb.STDOUT, filename_style)" \
+ "^\033\\\[34;41;2;27msome text\033\\\[m" \
+ "styled output, pass style by position"
+
+gdb_test "python write_and_flush(\"some text\", style='filename')" \
+ [multi_line \
+ "Python Exception <class 'TypeError'>: 'style' argument must be gdb\\.Style or None, not str\\." \
+ "Error occurred in Python: 'style' argument must be gdb\\.Style or None, not str\\."]
--
2.47.1