如何在DDD（或gdb）中用unique_ptr调试C ++ 11代码？ [英] How to debug C++11 code with unique_ptr in DDD (or gdb)?

问题描述

std :: unique_ptr 很好，但我发现它们在 DDD 或 gdb 。

我使用的gdb漂亮的打印机是gcc的一部分（例如， /usr/share/gcc-4.8.2/python/libstdcxx/v6/printers.py ）。例如：

  $ print pTest 
 std :: unique_ptr< MyType>包含0x2cef0a0 
  

然而，解引用指针不起作用：

  $ print * pTest 
无法找到运算符*。 
  

当我需要访问该值时，我必须手动复制指针并将其转换为正确的例如：

  print *（（MyType *）0x2cef0a0）
  

如果这个过程仍在运行，这个版本可以运行（仍然很丑但是更好）：

<$ p $如果分析核心转储

$ b $，print * pTest.get（）//将不起作用b

直接在DDD中 Display * pTest 的方法也行不通。它只会导致以下错误：

 <错误：找不到运算符*。> 
  

有没有办法在DDD中用unique_ptr调试C ++ 11代码（没有像我用繁琐的变通办法那样打破工作流程）？

---

我不害怕使用gdb命令，但DDD整合将是一个加号。例如，通过双击数据结构中的指针往往比打字更快。

我已经尝试删除漂亮的打印机，但它也不是最佳。我能想到的最好的是：

pre $ print pTest._M_t-> _M_head_impl


code>

解决方案

这个问题实际上与C ++ 11，unique_ptr或漂亮打印无关。问题是gcc不会发出std :: unique_ptr :: operator *的代码，可以通过gdb调用它来解引用unique_ptr。例如，如果你添加 * pTest; 到你的代码，那么gdb会执行解引用。

类似的问题是描述在SO后如何打印/评估c ++模板在gdb中运行。在 https://sourceware.org/上为auto_ptr描述了几乎相同的问题毫升/射手/ 2012-Q1 / msg00003.html 。如果我正确理解线程，则一种解决方法是修补漂亮的打印机，并在打印unique_ptr时打印出解除引用的指针。可以在 http://sourceware.org/bugzilla/show_bug上找到gdb错误报告。 cgi？id = 12937 。

gdb wiki位于 https://sourceware.org/gdb/wiki/STLSupport 描述了更漂亮的打印解决方案，可以有其他解决方法。

编辑：一个更优雅的解决方案，迫使编译器为包括operator *在内的所有成员模板发出代码，就是显式实例化类：

 模板class std :: unique_ptr< MyType>; 
  

std::unique_ptr are nice, but I find them less comfortable when debugging in DDD or gdb.

I'm using the gdb pretty printers that are part of gcc (e.g., /usr/share/gcc-4.8.2/python/libstdcxx/v6/printers.py). That is a big win for readability, for example:

$ print pTest
std::unique_ptr<MyType> containing 0x2cef0a0

However, dereferencing the pointer does not work:

$ print *pTest
Could not find operator*.

When I need to access the value, I have to manually copy the pointer and cast it to the correct type, for example:

print *((MyType*) 0x2cef0a0)

If the process is still running, this version works (still ugly but better):

print *pTest.get() // will not work if analyzing a core dump

The straightforward approach to Display *pTest in DDD does not work either. It only results in the following error:

<error: Could not find operator*.>

Is there a way to debug C++11 code with unique_ptr in DDD (without breaking the workflow like I do with my cumbersome workarounds)?

---

I'm not afraid to use gdb commands, but DDD integration would be a plus. For example, following pointers in data structures by just double-clicking on them is often faster than typing.

I already tried to drop the pretty printer, but it is also not optimal. The best that I could come up with is the following:

 print pTest._M_t->_M_head_impl

解决方案

This problem is actually not related to C++11, unique_ptr or pretty printing. The problem is that gcc does not emit code for std::unique_ptr::operator* that could be called by gdb to dereference the unique_ptr. If you for instance add *pTest; to your code then gdb does perform the dereferencing.

A similar problem is described in the SO post How to `print`/evaluate c++ template functions in gdb. Almost the same problem is described for an auto_ptr at https://sourceware.org/ml/archer/2012-q1/msg00003.html. If I understand the thread correctly one workaround would be to patch the pretty printer and also print out the dereferenced pointer when printing the unique_ptr. A gdb bug report can be found at http://sourceware.org/bugzilla/show_bug.cgi?id=12937.

The gdb wiki at https://sourceware.org/gdb/wiki/STLSupport describes more pretty printing solutions, which could have other workarounds.

Edit: A more elegant solution forcing the compiler to emit code for all member templates including operator* is to explicitly instantiate the class:

template class std::unique_ptr<MyType>;

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