`gdb` 无法展开堆栈 [英] `gdb` unable to unwind a stack
问题描述
考虑以下(损坏的)代码:
Consider following (broken) code:
#include <iostream>
#include <memory>
using namespace std;
class Test {
public:
unique_ptr<string> s;
Test() : s(NULL) {
}
void update(string& st) {
s = unique_ptr<string>(&(st));
}
};
void update(Test& t) {
string s("Hello to you");
t.update(s);
}
int main() {
Test t;
update(t);
cout << *t.s << endl;
}
这里我们在方法 Test::update() 中有错误，我们没有制作对象的 uniq 副本.所以当程序在macOS下运行时，你会得到:
Here we have error in method Test::update() we do not make a uniq copy of an object. So when the program is run under macOS, you'll get:
$ ./test
Hello t��E]�
test(44981,0x7fff99ba93c0) malloc: *** error for object 0x7fff5d45b690: pointer being freed was not allocated
*** set a breakpoint in malloc_error_break to debug
[1] 44981 abort ./test
我已经能够使用 lldb 成功调试此案例.即使没有在 malloc_error_break 中设置断点，也只是运行应用程序直到它被 SIGABRT 处理程序捕获.
I've been able to to debug this case successfully using lldb. Even without setting a breakpoint in malloc_error_break, just running application until it gets caught in SIGABRT handler.
lldb ./test
(lldb) target create "./test"
Current executable set to './test' (x86_64).
(lldb) run
Process 44993 launched: './test' (x86_64)
Hello t��_�
test(44993,0x7fff99ba93c0) malloc: *** error for object 0x7fff5fbff680: pointer being freed was not allocated
*** set a breakpoint in malloc_error_break to debug
Process 44993 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = signal SIGABRT
frame #0: 0x00007fff90d6cd42 libsystem_kernel.dylib`__pthread_kill + 10
libsystem_kernel.dylib`__pthread_kill:
-> 0x7fff90d6cd42 <+10>: jae 0x7fff90d6cd4c ; <+20>
0x7fff90d6cd44 <+12>: movq %rax, %rdi
0x7fff90d6cd47 <+15>: jmp 0x7fff90d65caf ; cerror_nocancel
0x7fff90d6cd4c <+20>: retq
Target 0: (test) stopped.
(lldb) bt
* thread #1, queue = 'com.apple.main-thread', stop reason = signal SIGABRT
* frame #0: 0x00007fff90d6cd42 libsystem_kernel.dylib`__pthread_kill + 10
frame #1: 0x00007fff90e5a457 libsystem_pthread.dylib`pthread_kill + 90
frame #2: 0x00007fff90cd2420 libsystem_c.dylib`abort + 129
frame #3: 0x00007fff90dc1fe7 libsystem_malloc.dylib`free + 530
frame #4: 0x0000000100001f7b test`Test::~Test() [inlined] std::__1::default_delete<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >::operator(this=0x00007fff5fbff730, __ptr="ax94x99�x7f ��_�x7f x80�_�x7f 0�_�x7f 0�_�x7f 0�_�x7f 0�_�x7f 0�_�x7f ��_�x7f x15x1e x01 x80�_�x7f
0")(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >*) const at memory:2397
frame #5: 0x0000000100001f46 test`Test::~Test() [inlined] std::__1::unique_ptr<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, std::__1::default_delete<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > > >::reset(this=0x00007fff5fbff730, __p="") at memory:2603
frame #6: 0x0000000100001ef3 test`Test::~Test() [inlined] std::__1::unique_ptr<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, std::__1::default_delete<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > > >::~unique_ptr(this=0x00007fff5fbff730) at memory:2571
frame #7: 0x0000000100001ef3 test`Test::~Test() [inlined] std::__1::unique_ptr<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, std::__1::default_delete<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > > >::~unique_ptr(this=0x00007fff5fbff730) at memory:2571
frame #8: 0x0000000100001ef3 test`Test::~Test(this=0x00007fff5fbff730) at main.cpp:6
frame #9: 0x0000000100001e15 test`Test::~Test(this=0x00007fff5fbff730) at main.cpp:6
frame #10: 0x0000000100001ab6 test`main at main.cpp:28
frame #11: 0x00007fff90c3e235 libdyld.dylib`start + 1
现在我发现问题出在 Test 析构函数中，从这里开始就是小菜一碟了.
Now I see that the problem is in Test destructor, and from here it's a piece of cake.
不幸的是，尝试在 macOS 下使用 gdb 调试此案例完全失败.这是我所做的:
Unfortunately, trying to debug this case using gdb under macOS was a total failure. Here is what I've done:
$ gdb ./test
GNU gdb (GDB) 8.0.1
Copyright (C) 2017 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law. Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-apple-darwin16.7.0".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from test...Reading symbols from /Users/bazhenov/Developer/linear-counter/tests/test/test.dSYM/Contents/Resources/DWARF/test...done.
done.
(gdb) run
Starting program: /Users/bazhenov/Developer/linear-counter/tests/test/test
[New Thread 0x1403 of process 45204]
warning: unhandled dyld version (15)
Hello tQ�_�
test(45204,0x7fff99ba93c0) malloc: *** error for object 0x7fff5fbff650: pointer being freed was not allocated
*** set a breakpoint in malloc_error_break to debug
Thread 2 received signal SIGABRT, Aborted.
0x00007fff90d6cd42 in ?? ()
(gdb) bt
#0 0x00007fff90d6cd42 in ?? ()
#1 0x00007fff90e5a457 in ?? ()
#2 0x00007fff5fbff590 in ?? ()
#3 0x0000030700000000 in ?? ()
#4 0x00007fff5fbff590 in ?? ()
#5 0x00007fff5fbff650 in ?? ()
#6 0x00007fff5fbff5a0 in ?? ()
#7 0x00007fff90cd2420 in ?? ()
#8 0xffffffff00000018 in ?? ()
#9 0x00007fff5fbff5b0 in ?? ()
#10 0x00007fffffffffdf in ?? ()
#11 0x00000001000c4000 in ?? ()
#12 0x00007fff5fbff5f0 in ?? ()
#13 0x00007fff90dc1fe7 in ?? ()
#14 0x378b45e65b700074 in ?? ()
#15 0x00007fff99ba00ac in ?? ()
#16 0x0000000000000000 in ?? ()
(gdb)
问题是:为什么 gdb 无法正确展开堆栈，如果我需要使用 gdb 获得正确的回溯，我有什么选择?
The question is: why gdb fails to unwind the stack correctly and what options do I have if I need to get correct backtrace using gdb?
推荐答案
为什么 gdb 无法正确展开堆栈
why gdb fails to unwind the stack correctly
在使用 gdb 的 Mac OS X Sierra 上存在一些问题，请参阅 这篇文章 和 gdb 错误报告.
There are some problems on Mac OS X Sierra with gdb, see this post and gdb bug report.
如果我需要使用 gdb 获得正确的回溯，我有什么选择
what options do I have if I need to get correct backtrace using gdb
您可以尝试降级Mac OS(不知道是否可以)或尝试应用临时破解补丁来自上述错误报告.
You can try to downgrade Mac OS (don't know whether is it possible) or try to apply temporary hack patch from above bug report.
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