GDB/LLDB debugger pretty printers w/QString support and vscode launch config (#18960)
* GDB/LLDB debugger pretty printers w/QString support and vscode launch config * Python code now adheres to pep8. Slight refactor to lldb printer for readability. * Resolved a few missed trailing whitespace errors from pylint * Added missing trailing newline I missed in my last commit * Apply suggestions from code review --------- Co-authored-by: Chris Hennes <chennes@pioneerlibrarysystem.org>
This commit is contained in:
Boots
48
contrib/.vscode/launch.json
vendored
48
contrib/.vscode/launch.json
vendored
@@ -16,10 +16,30 @@
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],
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"linux": {
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"MIMode": "gdb",
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"miDebuggerPath": "/usr/bin/gdb"
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"miDebuggerPath": "/usr/bin/gdb",
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"setupCommands": [
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{
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"description": "Load QT pretty-printers for GDB",
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"text": "python import sys; sys.path.append('${workspaceFolder}/contrib/debugger'); from qt_pretty_printers_gdb import register_qt_printers; register_qt_printers()",
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"ignoreFailures": false
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},
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{
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"description": "Enable pretty-printing for GDB",
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"text": "-enable-pretty-printing",
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"ignoreFailures": true
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},
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{
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"description": "Set Disassembly Flavor to Intel",
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"text": "-gdb-set disassembly-flavor intel",
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"ignoreFailures": true
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}
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]
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},
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"osx": {
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"MIMode": "lldb"
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"MIMode": "lldb",
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"preRunCommands": [
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"command script import ${workspaceFolder}/contrib/debugger/qt_pretty_printers_lldb.py"
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]
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},
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"stopAtEntry": false,
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"externalConsole": false,
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@@ -47,10 +67,30 @@
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],
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"linux": {
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"MIMode": "gdb",
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"miDebuggerPath": "/usr/bin/gdb"
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"miDebuggerPath": "/usr/bin/gdb",
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"setupCommands": [
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{
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"description": "Load QT pretty-printers for GDB",
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"text": "python import sys; sys.path.append('${workspaceFolder}/contrib/debugger'); from qt_pretty_printers_gdb import register_qt_printers; register_qt_printers()",
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"ignoreFailures": false
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},
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{
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"description": "Enable pretty-printing for GDB",
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"text": "-enable-pretty-printing",
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"ignoreFailures": true
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},
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{
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"description": "Set Disassembly Flavor to Intel",
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"text": "-gdb-set disassembly-flavor intel",
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"ignoreFailures": true
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}
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]
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},
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"osx": {
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"MIMode": "lldb"
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"MIMode": "lldb",
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"preRunCommands": [
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"command script import ${workspaceFolder}/contrib/debugger/qt_pretty_printers_lldb.py"
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]
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},
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"stopAtEntry": false,
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"externalConsole": false,
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124
contrib/debugger/qt_pretty_printers_gdb.py
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124
contrib/debugger/qt_pretty_printers_gdb.py
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@@ -0,0 +1,124 @@
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# pylint: disable=line-too-long
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"""
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QT Pretty Printer for GDB
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Currently supports displaying the following QT types in the debugger
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* QString
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Can be used from GDB via:
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(gdb) python
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>import sys
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>sys.path.insert(0, '{Your FreeCAD source dir}/contrib/debugger')
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>from qt_pretty_printers_gdb import register_qt_printers
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>register_qt_printers()
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>end
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QT pretty-printer script loaded.
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QT pretty-printer registered.
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(gdb) run
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*breakpoint*
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(gdb) p testString
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$1 = This is a QString in the debugger!
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(gdb)
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Can be used in VSCode via launch.json
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{
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"version": "0.2.0",
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"configurations": [
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{
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"name": "(gdb) Launch",
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"type": "cppdbg",
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"request": "launch",
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"program": "${workspaceFolder}/build/bin/FreeCAD",
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"args": [],
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"stopAtEntry": true,
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"cwd": "${workspaceFolder}/build",
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"environment": [],
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"externalConsole": false,
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"MIMode": "gdb",
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"setupCommands": [
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{
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"description": "Load QT pretty-printers for GDB",
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"text": "python import sys; sys.path.append('${workspaceFolder}/contrib/debugger'); from qt_pretty_printers_gdb import register_qt_printers; register_qt_printers()",
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"ignoreFailures": false
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},
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{
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"description": "Enable pretty-printing for gdb",
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"text": "-enable-pretty-printing",
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"ignoreFailures": true
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},
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{
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"description": "Set Disassembly Flavor to Intel",
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"text": "-gdb-set disassembly-flavor intel",
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"ignoreFailures": true
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}
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],
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"miDebuggerPath": "/usr/bin/gdb"
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}
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]
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}
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Note: There may be variances between different operating systems and/or build configurations
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in how QString data is stored internally. This was tested on debian12/amd64. @BootsSiR
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"""
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# pylint: enable=line-too-long
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import gdb
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class QStringPrinter:
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"""Pretty-printer class for QString objects in GDB."""
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def __init__(self, val):
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self.val = val
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def to_string(self):
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"""Pretty-printer function for QString objects in LLDB."""
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try:
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d = self.val["d"]
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if d == 0:
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return 'null'
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offset = int(d["offset"])
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data_ptr = d.cast(gdb.lookup_type("char").pointer()) + offset
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char16_t_ptr = data_ptr.cast(gdb.lookup_type("char16_t").pointer())
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string_data = []
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i = 0
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while char16_t_ptr[i] != 0:
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string_data.append(chr(char16_t_ptr[i]))
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i += 1
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return "".join(string_data)
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except gdb.error as e:
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if "Cannot access memory at address" in str(e):
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return "<uninitialized>"
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return f"<error: {str(e)}>"
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except Exception as e: # pylint: disable=broad-except
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return f"<unexpected error: {str(e)}>"
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def lookup_function(val):
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"""Maps a type to the appropriate pretty printer"""
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try:
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qstring_type = gdb.lookup_type("QString")
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if val.type.strip_typedefs() == qstring_type:
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return QStringPrinter(val)
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return None
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except gdb.error:
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return None
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def register_qt_printers(objfile=None):
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"""Register the QString pretty-printer with GDB."""
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if objfile is None:
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objfile = gdb.current_objfile()
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# Check if the printer is already registered
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if not any(printer == lookup_function for printer in gdb.pretty_printers): # pylint: disable=comparison-with-callable
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print("QT pretty-printer script loaded.")
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gdb.pretty_printers.append(lookup_function)
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print("QT pretty-printer registered.")
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107
contrib/debugger/qt_pretty_printers_lldb.py
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107
contrib/debugger/qt_pretty_printers_lldb.py
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@@ -0,0 +1,107 @@
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# pylint: disable=line-too-long
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"""
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QT Pretty Printer for LLDB
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Currently supports displaying the following QT types in the debugger
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* QString
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Can be used from LLDB via:
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(lldb) command script import {Your FreeCAD source dir}/contrib/debugger/qt_pretty_printers_lldb.py
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(lldb) frame variable test
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(QString) test = "This is a test string."
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(lldb)
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Can be used in VSCode via launch.json (tested with CodeLLDB extension)
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{
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"version": "0.2.0",
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"configurations": [
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{
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"type": "lldb",
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"request": "launch",
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"name": "Debug LLDB",
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"stopOnEntry": false,
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"program": "${workspaceFolder}/build/bin/FreeCAD",
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"args": [],
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"cwd": "${workspaceFolder}/build/",
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"preLaunchTask": "CMake: build",
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"preRunCommands": [
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"command script import ${workspaceFolder}/contrib/debugger/qt_pretty_printers_lldb.py"
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]
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}
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]
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}
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Note: There may be variances between different operating systems and/or build configurations
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in how QString data is stored internally. This was tested on debian12/amd64 and
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macOS/arm64. @BootsSiR
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"""
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# pylint: enable=line-too-long
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import lldb
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def QStringPrinter(val, _internal_dict):
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"""Pretty-printer for QString objects in LLDB."""
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try:
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# Access the 'd' member of QString
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d = val.GetChildMemberWithName("d")
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if not d.IsValid():
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return 'null'
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# some machines have a different QString object layout (macOS? arm64?) so
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# first we must check if a ptr member exists
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ptr_field = d.GetChildMemberWithName("ptr")
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# if the ptr member exists, we will use that as the base address for our text data.
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if ptr_field.IsValid():
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# use the ptr value
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data_base_address = ptr_field.GetValueAsUnsigned()
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else:
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# we don't have a ptr member, so let's use an offset from the address of the
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# QString::Data as our base address
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d_address = d.GetValueAsUnsigned()
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# Assume the string data starts immediately after the first 24 bytes
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data_base_address = d_address + 24
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# if at this point, we don't have a valid data base address
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# we cannot proceed
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if data_base_address == 0:
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return "null"
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# Initialize variables for memory reading
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process = val.GetTarget().GetProcess()
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error = lldb.SBError()
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chunk_size = 256 # Size of each memory chunk to read
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string_data = []
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offset = 0
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# Read memory in chunks until null-terminator is found
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while True:
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raw_data = process.ReadMemory(data_base_address + offset, chunk_size, error)
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if not error.Success():
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return f"<error: unable to read memory: {error.GetCString()}>"
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# Parse UTF-16 data from the chunk
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for i in range(0, len(raw_data), 2): # char16_t is 2 bytes
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char16_val = int.from_bytes(raw_data[i:i+2], byteorder='little')
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if char16_val == 0: # Null-terminator found
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return f'"{ "".join(string_data) }"'
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string_data.append(chr(char16_val))
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# Increase the offset for the next chunk
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offset += chunk_size
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except Exception as e: # pylint: disable=broad-except
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return f"<error: {str(e)}>"
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def __lldb_init_module(debugger, _internal_dict):
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"""Register the QString pretty-printer with LLDB."""
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print("QT pretty-printer script loaded.")
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debugger.HandleCommand('type summary add QString -F qt_pretty_printers_lldb.QStringPrinter')
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print("QT pretty-printer registered.")
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