为什么`gdb`看不到全局变量？

Question

请参阅如何gdb无法打印全局变量dictionary在下面的代码：

m@m-X555LJ ~ $ cat 148.cc 
#include <iostream> 
#include <string> 
#include <vector> 
#include <array> 
#include <utility> 
#include <algorithm> 
#include <sstream> 
using namespace std; 

using letters = array<int, 26>; 
letters emptylet = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}; 
vector<pair<string, letters>> dictionary; 

void backtrace(string &orig, vector<string> &phrase, vector<string> &acc, letters &curr, letters &goal, decltype(dictionary)::iterator it) { 
    if(it == dictionary.end()) 
    return; 
    for(int i = 0; i < it->second.size(); i++) 
    curr[i] += it->second[i]; 
    acc.push_back(it->first); 
    bool all_same = true; 
    for(int i = 0; i < curr.size(); i++) 
    if(curr[i] > goal[i]) 
     goto clean; 
    else if(curr[i] != goal[i]) 
     all_same = false; 
    if(all_same) { 
    if(acc != phrase) { 
     cout << orig << " ="; 
     for(string word: acc) 
     cout << ' ' << word; 
     cout << '\n'; 
    } 
    } else 
    backtrace(orig, phrase, acc, curr, goal, it+1); 
clean: 
    acc.pop_back(); 
    for(int i = 0; i < it->second.size(); i++) 
    curr[i] -= it->second[i]; 
    backtrace(orig, phrase, acc, curr, goal, it+1); 
} 

int main() 
{ 
    while((cin>>ws).peek()!='#') { 
    string word; 
    cin >> word; 
    letters let = emptylet; 
    for(char c: word) 
     let[c-'A']++; 
    dictionary.push_back(make_pair(word, let)); 
    } 
    while((cin>>ws).peek()!='#') { 
    string s; 
    getline(cin, s); 
    string orig = s; 
    stringstream ss(s+'\n'); 
    vector<string> phrase; 
    while(cin>>s){ 
     phrase.push_back(s); 
    } 
    sort(phrase.begin(), phrase.end()); 
    letters let = emptylet; 
    for(string wrd: phrase) 
     for(char c: wrd) 
     let[c-'A']++; 
    vector<string> empt; 
    backtrace(orig, phrase, empt, emptylet, let, dictionary.begin()); 
    } 
} 
m@m-X555LJ ~ $ g++ -g -std=c++11 -o 148 148.cc 
m@m-X555LJ ~ $ cat 148.in 
ABC 
AND 
DEF 
DXZ 
K 
KX 
LJSRT 
LT 
PT 
PTYYWQ 
Y 
YWJSRQ 
ZD 
ZZXY 
# 
ZZXY ABC DEF 
SXZYTWQP KLJ YRTD 
ZZXY YWJSRQ PTYYWQ ZZXY 
# 
m@m-X555LJ ~ $ gdb ./148 
GNU gdb (Ubuntu 7.11.1-0ubuntu1~16.04) 7.11.1 
Copyright (C) 2016 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-linux-gnu". 
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 ./148...done. 
(gdb) break 52 
Breakpoint 1 at 0x401d0f: file 148.cc, line 52. 
(gdb) r < 148.in 
Starting program: /home/m/148 < 148.in 

Breakpoint 1, main() at 148.cc:52 
52 while((cin>>ws).peek()!='#') { 
(gdb) p dictionary 
No symbol "dictionary" in current context. 
(gdb) p di 
dictionary[abi:cxx11] dir_data     dirfd     dirstream.h    div      divmod_1.c 
difftime     dirent     dirfd.c     disallow_malloc_check div.c     divrem.c 
difftime.c    dirent.h     dirname     distinguish_extX   div_t      
digits_dots.c   dirent64     dirname.c    distinguish_extX.isra.0 divide     
(gdb) p dictionary[abi:cxx11] 
No symbol "dictionary" in current context. 
(gdb) quit 
A debugging session is active. 

    Inferior 1 [process 3815] will be killed. 

Quit anyway? (y or n) y 
m@m-X555LJ ~ $ g++ --version 
g++ (Ubuntu 5.4.0-6ubuntu1~16.04.4) 5.4.0 20160609 
Copyright (C) 2015 Free Software Foundation, Inc. 
This is free software; see the source for copying conditions. There is NO 
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. 

m@m-X555LJ ~ $ 

我不明白这一点。为什么会这样？ gdb有什么明显的我不知道？

据我最好的了解，p dictionary应该打印std::vector全局变量的内容，称为dictionary。

而这不是第一次发生在我身上的事情。我记得gdb没有看到函数，变量等。这次我决定记录这个案例。

Answer 1

你可以看到这个问题，当您使用p di标签标签（像你一样） - 由GCC产生的符号被称为“字典[ABI：cxx11]”，你可以通过输入p 'dict打印标签 - 请注意名称周围的引号以使gdb不尝试将[ .. ]解释为表达式。