一般來說，GDB主要完成下面四個方面的功能：
(1)啟動你的程序，可以按照你的自定義的要求隨心所欲的運行程序。
(2)可讓被調試的程序在你所指定的調置的斷點處停住。（斷點可以是條件表達式）
(3)當程序被停住時，可以檢查此時你的程序中所發生的事。
(4)動態的改變你程序的執行環境。
1、簡介
GDB是GNU開源組織發布的一個強大的UNIX下的程序調試工具。如果你是在 UNIX平台下做軟件，你會發現GDB這個調試工具有比VC、BCB的圖形化調試器更強大的功能。同時GDB也具有例如ddd這樣的圖形化的調試端。
2、調試C/C++程序
直接上代碼了
#include<iostream>
using namespace std;
long factorial(int n);
int main()
{
int n(0);
cin>>n;
long val=factorial(n);
cout<<val<<endl;
cin.get();
return 0;
}
long factorial(int n)
{
long result(1);
while(n--)
{
result*=n;
}
return result;
}
編譯
1
g++ k.cpp -g -Wall -Werror -o main
開始調試
[root@localhost code]# gdb ./main
GNU gdb (GDB) Red Hat Enterprise Linux (7.2-83.el6)
Copyright (C) 2010 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 "i686-redhat-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /code/main...done.
(gdb) l
warning: Source file is more recent than executable.
1 #include<iostream>
2 using namespace std;
3 long factorial(int n);
4
5 int main()
6 {
7 int n(0);
8 cin>>n;
9 long val=factorial(n);
10 cout<<val<<endl;
(gdb)
設置斷點 break linenumber
(gdb) b 9 Breakpoint 1 at 0x80486f9: file k.cpp, line 9. (gdb) r Starting program: /code/main 4 Breakpoint 1, main () at k.cpp:9 9 long val=factorial(n);
設置觀察點 watch var
(gdb) s
factorial (n=4) at k.cpp:17
17 long result(1);
(gdb) l
12 return 0;
13 }
14
15 long factorial(int n)
16 {
17 long result(1);
18 while(n--)
19 {
20 result*=n;
21 }
(gdb) watch n
Hardware watchpoint 2: n
(gdb) watch result
Hardware watchpoint 3: result
(gdb) c
Continuing.
Hardware watchpoint 3: result
Old value = 0
New value = 1
factorial (n=4) at k.cpp:18
18 while(n--)
(gdb)
Continuing.
Hardware watchpoint 2: n
Old value = 4
New value = 3
0x08048764 in factorial (n=3) at k.cpp:18
18 while(n--)
(gdb)
Continuing.
Hardware watchpoint 3: result
Old value = 1
New value = 3
factorial (n=3) at k.cpp:18
18 while(n--)
(gdb)
Continuing.
Hardware watchpoint 2: n
Old value = 3
New value = 2
0x08048764 in factorial (n=2) at k.cpp:18
18 while(n--)
(gdb)
Continuing.
Hardware watchpoint 3: result
Old value = 3
New value = 6
factorial (n=2) at k.cpp:18
18 while(n--)
(gdb)
Continuing.
Hardware watchpoint 2: n
Old value = 2
New value = 1
0x08048764 in factorial (n=1) at k.cpp:18
18 while(n--)
(gdb)
Continuing.
Hardware watchpoint 2: n
Old value = 1
New value = 0
0x08048764 in factorial (n=0) at k.cpp:18
18 while(n--)
(gdb)
Continuing.
Watchpoint 2 deleted because the program has left the block in
which its expression is valid.
Watchpoint 3 deleted because the program has left the block in
which its expression is valid.
0x08048705 in main () at k.cpp:9
9 long val=factorial(n);
(gdb) p val
$1 = 11476980
(gdb)
可以看到是while那裡，導致n越界了，fix
while(n>0) //doesn't let n reach 0
{
result*=n;
n--; //decrements only after the evaluation
}
一些快捷命令
l – list
p – print print {variable}
c – continue
s – step
b - break break line_number/break [file_name]:line_number/break [file_name]:func_name
r - run
set <var> = <value>
watch <var>
ENTER: pressing enter key would execute the previously executed command again.
c/n/s的區別
•c or continue: Debugger will continue executing until the next break point.
•n or next: Debugger will execute the next line as single instruction.
•s or step: Same as next, but does not treats function as a single instruction, instead goes into the function and executes it line by line
3、調試PHP程序
PHP代碼
<?php.
for($i = 0; $i < 10; $i++){
echo $i."\n";
sleep(3);
if(in_array($i,[1,9,20])){
print_r($i*$i);
var_dump($i*$i);
print $i*$i;
}
}
開始調試，加上斷點
[root@localhost code]# gdb php GNU gdb (GDB) Red Hat Enterprise Linux (7.2-83.el6) Copyright (C) 2010 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 "i686-redhat-linux-gnu". For bug reporting instructions, please see: <http://www.gnu.org/software/gdb/bugs/>... Reading symbols from /usr/bin/php...done. (gdb) b zif_sleep Breakpoint 1 at 0x8435180: file /usr/local/src/php-5.5.23/ext/standard/basic_functions.c, line 4449. (gdb) b zif_in_array Breakpoint 2 at 0x8426923: file /usr/local/src/php-5.5.23/ext/standard/array.c, line 1215. (gdb) b zif_print_r Breakpoint 3 at 0x8438273: file /usr/local/src/php-5.5.23/ext/standard/basic_functions.c, line 5553. (gdb) b zif_var_dump Breakpoint 4 at 0x847d296: file /usr/local/src/php-5.5.23/ext/standard/var.c, line 178. (gdb) b zif_printf Function "zif_printf" not defined. Make breakpoint pending on future shared library load? (y or [n]) n (gdb) b zif_sprintf Function "zif_sprintf" not defined. Make breakpoint pending on future shared library load? (y or [n]) n (gdb) b printf Breakpoint 5 at 0x806a390 (gdb) b memcpy Breakpoint 6 at 0x8069390 (gdb) b zif_print Function "zif_print" not defined. Make breakpoint pending on future shared library load? (y or [n]) n (gdb) b zif_echo Function "zif_echo" not defined. Make breakpoint pending on future shared library load? (y or [n]) n (gdb) info b Num Type Disp Enb Address What 1 breakpoint keep y 0x08435180 in zif_sleep at /usr/local/src/php-5.5.23/ext/standard/basic_functions.c:4449 2 breakpoint keep y 0x08426923 in zif_in_array at /usr/local/src/php-5.5.23/ext/standard/array.c:1215 3 breakpoint keep y 0x08438273 in zif_print_r at /usr/local/src/php-5.5.23/ext/standard/basic_functions.c:5553 4 breakpoint keep y 0x0847d296 in zif_var_dump at /usr/local/src/php-5.5.23/ext/standard/var.c:178 5 breakpoint keep y 0x0806a390 <printf@plt> 6 breakpoint keep y 0x08069390 <memcpy@plt> (gdb)
加幾個斷點測試一下 syntax：break [file_name]:func_name，這裡大致可以看一下 echo print等不是函數了
然後開始調試
(gdb) p *return_value
$1 = {value = {lval = 1515870810, dval = 1.7838867517321418e+127, str = {val = 0x5a5a5a5a <Address 0x5a5a5a5a out of bounds>,
len = 1515870810}, ht = 0x5a5a5a5a, obj = {handle = 1515870810, handlers = 0x5a5a5a5a}}, refcount__gc = 1, type = 0 '\000', is_ref__gc = 0 '\000'}
(gdb) p return_value->value
$2 = {lval = 1515870810, dval = 1.7838867517321418e+127, str = {val = 0x5a5a5a5a <Address 0x5a5a5a5a out of bounds>,
len = 1515870810}, ht = 0x5a5a5a5a, obj = {handle = 1515870810, handlers = 0x5a5a5a5a}}
(gdb) p return_value->value->lval
$3 = 1515870810
我們還可以使用內置的gdbinit來調試
(gdb) source /usr/local/src/php-5.5.23/.gdbinit (gdb) zbacktrace [0xb7fa1144] sleep(3) /code/kk.php:4
查看當前堆棧，PHP內核的執行過程
(gdb) bt #0 zif_sleep (ht=1, return_value=0xb7fbd6f0, return_value_ptr=0x0, this_ptr=0x0, return_value_used=0) at /usr/local/src/php-5.5.23/ext/standard/basic_functions.c:4449 #1 0x085f6870 in execute_internal (execute_data_ptr=0xb7fa1144, fci=0x0, return_value_used=0) at /usr/local/src/php-5.5.23/Zend/zend_execute.c:1484 #2 0x085aea5f in dtrace_execute_internal (execute_data_ptr=0xb7fa1144, fci=0x0, return_value_used=0) at /usr/local/src/php-5.5.23/Zend/zend_dtrace.c:97 #3 0x00935c33 in pt_execute_core (internal=1, execute_data=0xb7fa1144, fci=0x0, rvu=0) at /usr/local/src/trace-0.3.0/extension/trace.c:941 #4 0x00935e49 in pt_execute_internal (execute_data=0xb7fa1144, fci=0x0, return_value_used=0) at /usr/local/src/trace-0.3.0/extension/trace.c:1005 #5 0x085f7523 in zend_do_fcall_common_helper_SPEC (execute_data=0xb7fa1144) at /usr/local/src/php-5.5.23/Zend/zend_vm_execute.h:552 #6 0x085fb2a9 in ZEND_DO_FCALL_SPEC_CONST_HANDLER (execute_data=0xb7fa1144) at /usr/local/src/php-5.5.23/Zend/zend_vm_execute.h:2332 #7 0x085f6deb in execute_ex (execute_data=0xb7fa1144) at /usr/local/src/php-5.5.23/Zend/zend_vm_execute.h:363 #8 0x085ae9dc in dtrace_execute_ex (execute_data=0xb7fa1144) at /usr/local/src/php-5.5.23/Zend/zend_dtrace.c:73 #9 0x00935c5e in pt_execute_core (internal=0, execute_data=0xb7fa1144, fci=0x0, rvu=0) at /usr/local/src/trace-0.3.0/extension/trace.c:946 #10 0x00935e10 in pt_execute_ex (execute_data=0xb7fa1144) at /usr/local/src/trace-0.3.0/extension/trace.c:1000 #11 0x085f6e4a in zend_execute (op_array=0xb7fbc7b4) at /usr/local/src/php-5.5.23/Zend/zend_vm_execute.h:388 #12 0x085c1cf2 in zend_execute_scripts (type=8, retval=0x0, file_count=3) at /usr/local/src/php-5.5.23/Zend/zend.c:1327 #13 0x085470f9 in php_execute_script (primary_file=0xbffff4a4) at /usr/local/src/php-5.5.23/main/main.c:2525 #14 0x0865af46 in do_cli (argc=2, argv=0x8b9b908) at /usr/local/src/php-5.5.23/sapi/cli/php_cli.c:994 #15 0x0865bff3 in main (argc=2, argv=0x8b9b908) at /usr/local/src/php-5.5.23/sapi/cli/php_cli.c:1378
查看代碼段
(gdb) l
4444 Delay for a given number of seconds */
4445 PHP_FUNCTION(sleep)
4446 {
4447 long num;
4448
4449 if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "l", &num) == FAILURE) {
4450 RETURN_FALSE;
4451 }
4452 if (num < 0) {
4453 php_error_docref(NULL TSRMLS_CC, E_WARNING, "Number of seconds must be greater than or equal to 0");
(gdb) l 4450
4445 PHP_FUNCTION(sleep)
4446 {
4447 long num;
4448
4449 if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "l", &num) == FAILURE) {
4450 RETURN_FALSE;
4451 }
4452 if (num < 0) {
4453 php_error_docref(NULL TSRMLS_CC, E_WARNING, "Number of seconds must be greater than or equal to 0");
4454 RETURN_FALSE;
(gdb) l zif_usleep
4463 /* }}} */
4464
4465 /* {{{ proto void usleep(int micro_seconds)
4466 Delay for a given number of micro seconds */
4467 PHP_FUNCTION(usleep)
4468 {
4469 #if HAVE_USLEEP
4470 long num;
4471
4472 if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "l", &num) == FAILURE) {
繼續執行
(gdb) n
4452 if (num < 0) {
(gdb) p num
$6 = 3
(gdb) n
4457 RETURN_LONG(php_sleep(num));
(gdb) n
4462 }
(gdb) n
execute_internal (execute_data_ptr=0xb7fa1144, fci=0x0, return_value_used=0) at /usr/local/src/php-5.5.23/Zend/zend_execute.c:1488
1488 }
到了execute_internal ，可以查看一下當前函數的一個狀態
(gdb) p execute_data_ptr
$7 = (zend_execute_data *) 0xb7fa1144
(gdb) p *execute_data_ptr
$8 = {opline = 0xb7fbcacc, function_state = {function = 0x8bcf3e8, arguments = 0xb7fa119c}, op_array = 0xb7fbc7b4, object = 0x0,
symbol_table = 0x8b99cdc, prev_execute_data = 0x0, old_error_reporting = 0x0, nested = 0 '\000',
original_return_value = 0x38b4ac9, current_scope = 0x49, current_called_scope = 0x45, current_this = 0x0, fast_ret = 0x0,
call_slots = 0xb7fa1188, call = 0xb7fa1188}
(gdb) p *execute_data_ptr->function_state.function->common->function_name
$9 = 115 's'
(gdb) p execute_data_ptr->function_state.function->common->function_name
$10 = 0x8af03c9 "sleep"
(gdb) p execute_data_ptr->op_array->filename
$11 = 0xb7fbc8e8 "/code/kk.php"
查看當前hashtable
(gdb) p *execute_data_ptr->symbol_table
$ = {nTableSize = , nTableMask = , nNumOfElements = , nNextFreeElement = , pInternalPointer = xbfbc,
pListHead = xbfbc, pListTail = xbfbd, arBuckets = xbfb, pDestructor = xbff <_zval_ptr_dtor_wrapper>,
persistent = '\', nApplyCount = '\', bApplyProtection = '\', inconsistent = }
繼續執行輸出c之後，回車即可，同樣可以看到in_array的執行信息
(gdb) p *execute_data_ptr->function_state.function
$24 = {type = 1 '\001', common = {type = 1 '\001', function_name = 0x8af1841 "in_array", scope = 0x0, fn_flags = 256,
prototype = 0x0, num_args = 3, required_num_args = 2, arg_info = 0x8ae7554}, op_array = {type = 1 '\001',
function_name = 0x8af1841 "in_array", scope = 0x0, fn_flags = 256, prototype = 0x0, num_args = 3, required_num_args = 2,
arg_info = 0x8ae7554, refcount = 0x842691d, opcodes = 0x8bcf120, last = 0, vars = 0x0, last_var = 0, T = 1,
nested_calls = 3086618796, used_stack = 0, brk_cont_array = 0x0, last_brk_cont = 1, try_catch_array = 0xb7fa10dd,
last_try_catch = 96, has_finally_block = 160 '\240', static_variables = 0x0, this_var = 11482064,
filename = 0xaf1ff4 "|\035\257", line_start = 11482016, line_end = 146381272,
doc_comment = 0xbffff238 "x\362\377\277\244\aY\b\021", doc_comment_len = 10305959, early_binding = 11085989,
literals = 0x8b7a0a0, last_literal = 140062666, run_time_cache = 0xb7fa10d4, last_cache_slot = 90, reserved = {0x9, 0x8b5f7ac,
0x796, 0x0}}, internal_function = {type = 1 '\001', function_name = 0x8af1841 "in_array", scope = 0x0, fn_flags = 256,
prototype = 0x0, num_args = 3, required_num_args = 2, arg_info = 0x8ae7554, handler = 0x842691d <zif_in_array>,
module = 0x8bcf120}}
(gdb) p execute_data_ptr->function_state.function->common->function_name
$26 = 0x8af1841 "in_array"
(gdb) p execute_data_ptr->op_array->filename
$27 = 0xb7fbc8e8 "/code/kk.php"
還可以加一下監控watch、設置一些調試變量set 等等
其他的調試工具還有 strace 查看系統調用、ltrace 查看類庫的調用、vld查看opcode。
以上內容是小編給大家分享的關於如何使用GDB調試PHP程序的全部內容，希望大家喜歡。
