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Background

I am trying to debug a C++ code that uses some personal dynamic libraries. I am using Mac OSX, but I am not using llvm/clang to compile my code nor the libraries. At the moment, I am using the GNU g++ compiler (4.7) provided by homebrew.

The problem

I have two choices of debuggers in this environment: the gdb version provided by Mac Developer Tools (GNU gdb 6.3.50-20050815 (Apple version gdb-1824)) and the gdb installed with homebrew (GNU gdb (GDB) 7.5.1). I would prefer to use the latter, but when using it, it shows many important variables as optimized out.

For example, this is an extract of the output of my program using gdb 7.5.1:

Breakpoint 1, MWE::Outputs (this=<optimized out>, time=<optimized out>)
    at /Users/ynet/temp/mwe.cpp:203
203     cout << "example" << endl;
(gdb) p this
$1 = <optimized out>

While gdb 6.3.50 shows:

Breakpoint 1, MWE::Outputs (this=0x100601080, time=0.64300000000000046) at /Users/ynet/temp/mwe.cpp:203
203     cout << "example" << endl;
(gdb) p this
$1 = (MWE * const) 0x100601080

Both programs are identical (i.e. it's the same executable); it has been compiled with the homebrew g++-4.7 and not the llvm/clang compiler provided by Apple Developer Tools. Unlike questions regarding the optimized out results of gdb, I have checked that I am compiling with '-O0' (my current flags are '-O0 -g -ggdb')

Question

Why do I get two different behaviors of gdb in this case and what should I do in order to use the most recent gdb version without the optimized values?

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1 回答 1

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为什么在这种情况下我会得到 gdb 的两种不同行为，我应该怎么做才能使用没有优化值的最新 gdb 版本？

<optimized out>GDB 打印未优化的代码显然是一个错误。

您应该尝试使用从主干构建的 GDB 重现此问题，创建一个显示问题的最小测试用例，并提交错误 bugzilla。

于 2013-03-21T20:21:28.757 回答