Xcode lldb 错误：无法打印出 Swift 变量 - 改为获取“$__lldb_injected_self.$__lldb_wrapped_expr_x”

Question

Sometimes, when trying to print out a variable in the debugger, the following error message is displayed:

error: warning: <EXPR>:12:9: warning: initialization of variable '$__lldb_error_result' was never used; consider replacing with assignment to '_' or removing it
    var $__lldb_error_result = __lldb_tmp_error
    ~~~~^~~~~~~~~~~~~~~~~~~~
    _

error: <EXPR>:18:5: error: use of unresolved identifier '$__lldb_injected_self'
    $__lldb_injected_self.$__lldb_wrapped_expr_120(     
    ^~~~~~~~~~~~~~~~~~~~~

This is a known lldb bug ( https://bugs.swift.org/browse/SR-6156 ), but perhaps someone knows a workaround that can be used until that bug is fixed?

Answer 1

As a workaround you can print it in the lldb debugger using:

frame variable variablename

Also possible using shortened syntax for quicker typing

fr v variablename

Since XCode 10.2 an ever simpler lldb syntax is supported:

v variable

Update - new workarounds:

Print stack addresses:

v -L variablename

po like on stack frame variable.property

 v -o variablename.property

Swift like p

e unsafeBitCast(address, to: ClassName.self)

Update2 - new workaround applicable for Swift classes being wrappers of objc classes.

Example:

v response
(HTTPURLResponse) response = 0x0000000283ba7640 {

if v works^:

e -l objc -- (int)[0x0000000283ba7640 statusCode]
(int) $2 = 404

I'd appreciate reports what is actually helpful and works. Thanks.

More information on this kind of capabilities can be found here: https://developer.apple.com/library/content/documentation/General/Conceptual/lldb-guide/chapters/C5-Examining-The-Call-Stack.html

Answer 2

清理项目并删除派生数据为我解决了这个问题。