From 58fe72ab83ab6490b9a09e71f5762f2a12bd2c5a Mon Sep 17 00:00:00 2001
From: Felix Morgner <felix.morgner@ost.ch>
Date: Sun, 30 Aug 2026 17:30:35 +0200
Subject: kstd/gdb: add error_code and result printers

---
 libs/kstd/gdb/__init__.py   | 10 ++++---
 libs/kstd/gdb/error_code.py | 66 +++++++++++++++++++++++++++++++++++++++++++++
 libs/kstd/gdb/result.py     | 51 +++++++++++++++++++++++++++++++++++
 3 files changed, 124 insertions(+), 3 deletions(-)
 create mode 100644 libs/kstd/gdb/error_code.py
 create mode 100644 libs/kstd/gdb/result.py

(limited to 'libs/kstd')

diff --git a/libs/kstd/gdb/__init__.py b/libs/kstd/gdb/__init__.py
index 0cdafffd..018b31f2 100644
--- a/libs/kstd/gdb/__init__.py
+++ b/libs/kstd/gdb/__init__.py
@@ -1,15 +1,17 @@
 import gdb.printing
 
 
-from .units import KstdBytesPrinter
-from .vector import KstdVectorPrinter
-from .string import KstdStringPrinter
+from .error_code import KstdErrorCodePrinter
+from .result import KstdResultPrinter
 from .smart_pointers import (
     KstdUniquePtrPrinter,
     KstdSharedPtrPrinter,
     KstdObserverPtrPrinter,
     KstdWeakPtrPrinter,
 )
+from .string import KstdStringPrinter
+from .units import KstdBytesPrinter
+from .vector import KstdVectorPrinter
 
 
 def build_pretty_printers():
@@ -22,6 +24,8 @@ def build_pretty_printers():
     pp.add_printer("observer_ptr", "^kstd::observer_ptr<.*>$", KstdObserverPtrPrinter)
     pp.add_printer("bytes", "^kstd::basic_unit<.*, kstd::bytes_tag, .*>$", KstdBytesPrinter)
     pp.add_printer("offset", "^kstd::basic_unit<.*, kstd::byte_offset_tag, .*>$", KstdBytesPrinter)
+    pp.add_printer("error_code", "^kstd::error_code$", KstdErrorCodePrinter)
+    pp.add_printer("result", "^std::expected<.*, kstd::error_code>$", KstdResultPrinter)
     return pp
 
 
diff --git a/libs/kstd/gdb/error_code.py b/libs/kstd/gdb/error_code.py
new file mode 100644
index 00000000..1569f59a
--- /dev/null
+++ b/libs/kstd/gdb/error_code.py
@@ -0,0 +1,66 @@
+import gdb
+
+
+class KstdErrorCodePrinter(gdb.ValuePrinter):
+    def __init__(self, val):
+        self.__val = val
+
+    def _error_value(self):
+        return int(self.__val["m_value"])
+
+    def _category_name(self):
+        try:
+            category_pointer = self.__val["m_category"]
+            if int(category_pointer) == 0:
+                return "<null category>"
+            category = category_pointer.dereference()
+            try:
+                dynamic = category.dynamic_type
+                name = str(dynamic)
+            except gdb.error:
+                name = str(category.type)
+            name = name.replace("(anonymous namespace)::", "")
+            if name.endswith("_t"):
+                name = name[:-2]
+            return name
+        except (gdb.error, AttributeError):
+            return "?"
+
+    def _message(self):
+        try:
+            category_pointer = self.__val["m_category"]
+            if int(category_pointer) == 0:
+                return None
+            value = self._error_value()
+            address = int(category_pointer)
+            result = gdb.parse_and_eval(
+                f"((kstd::error_category const *){address:#x})->message({value})"
+            )
+            try:
+                ptr = result["_M_str"]
+                length = int(result["_M_len"])
+                if int(ptr) != 0 and length > 0:
+                    return ptr.string(length=length)
+            except (gdb.error, AttributeError, KeyError):
+                pass
+            return str(result)
+        except (gdb.error, RuntimeError):
+            return None
+
+    def to_string(self):
+        value = self._error_value()
+        category = self._category_name()
+        msg = self._message()
+        if msg is not None:
+            return f"{category}:{value} ({msg})"
+        return f"{category}:{value}"
+
+    def children(self):
+        yield ("value", self.__val["m_value"])
+        category_pointer = self.__val["m_category"]
+        if int(category_pointer) != 0:
+            yield ("category", category_pointer.dereference())
+
+    def display_hint(self):
+        return None
+
diff --git a/libs/kstd/gdb/result.py b/libs/kstd/gdb/result.py
new file mode 100644
index 00000000..8cef0fed
--- /dev/null
+++ b/libs/kstd/gdb/result.py
@@ -0,0 +1,51 @@
+import gdb
+
+from .error_code import KstdErrorCodePrinter
+
+
+class KstdResultPrinter(gdb.ValuePrinter):
+    def __init__(self, val):
+        self.__val = val
+        self.__has_value = bool(val["_M_has_value"])
+        try:
+            t = val.type.template_argument(0)
+            self.__is_void = t.code == gdb.TYPE_CODE_VOID
+        except (gdb.error, AttributeError):
+            self.__is_void = False
+
+    @property
+    def _error_code(self):
+        return self.__val["_M_unex"]
+
+    @property
+    def _value(self):
+        return self.__val["_M_val"]
+
+    def _format_value(self, gdb_value):
+        printer = gdb.default_visualizer(gdb_value)
+        if printer is not None:
+            return printer.to_string()
+        s = str(gdb_value)
+        if s.startswith("{"):
+            return str(gdb_value.type.strip_typedefs())
+        return s
+
+    def _format_error(self, error_code_val):
+        printer = KstdErrorCodePrinter(error_code_val)
+        return printer.to_string()
+
+    def to_string(self):
+        if not self.__has_value:
+            return f"failure: {self._format_error(self._error_code)}"
+        if self.__is_void:
+            return "success"
+        return f"success: {self._format_value(self._value)}"
+
+    def children(self):
+        if not self.__has_value:
+            yield ("error", self._error_code)
+        elif not self.__is_void:
+            yield ("value", self._value)
+
+    def display_hint(self):
+        return None
-- 
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