[Php] use gdb to debug the php program and gdb to debug the php program _ PHP Tutorial-php Tutorial

[Php] use gdb to debug the php program and gdb to debug the php program. [Php] use gdb to Debug php programs. gdb to Debug php programs 1. introduction GDB is a powerful tool for debugging programs under UNIX released by the GNU open-source organization. If you are working on a UNIX platform, [php] uses gdb to debug the php program and gdb to debug the php program.
1. Introduction

GDB is a powerful UNIX program debugging tool released by the GNU open-source organization. If you are working on a UNIX platform, you will find that the GDB debugging tool has more powerful functions than the visual debugger of VC and BCB. At the same time, GDB also has a graphical debugging end such as ddd.

2. debug the C/C ++ program

Code directly

# Include
 
  
Using namespace std; long factorial (int n); int main () {int n (0); cin> n; long val = factorial (n); cout <
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Compile
   
g++ k.cpp -g -Wall -Werror -o main
   
Start Debugging
   
[Root @ localhost code] # gdb. /mainGNU 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
    
     
2 using namespace std; 3 long factorial (int n); 45 int main () 6 {7 int n (0); 8 cin> n; 9 long val = factorial (n); 10 cout <
     << pre>
      
Set the breakpoint break linenumber
      
(gdb) b 9Breakpoint 1 at 0x80486f9: file k.cpp, line 9.(gdb) rStarting program: /code/main 4Breakpoint 1, main () at k.cpp:99           long val=factorial(n);
      
Set watch var
      
(gdb) sfactorial (n=4) at k.cpp:1717          long result(1);(gdb) l12          return 0;13      }1415      long factorial(int n)16      {17          long result(1);18          while(n--)19          {20              result*=n;21          }(gdb) watch nHardware watchpoint 2: n(gdb) watch resultHardware watchpoint 3: result(gdb) cContinuing.Hardware watchpoint 3: resultOld value = 0New value = 1factorial (n=4) at k.cpp:1818          while(n--)(gdb) Continuing.Hardware watchpoint 2: nOld value = 4New value = 30x08048764 in factorial (n=3) at k.cpp:1818          while(n--)(gdb) Continuing.Hardware watchpoint 3: resultOld value = 1New value = 3factorial (n=3) at k.cpp:1818          while(n--)(gdb) Continuing.Hardware watchpoint 2: nOld value = 3New value = 20x08048764 in factorial (n=2) at k.cpp:1818          while(n--)(gdb) Continuing.Hardware watchpoint 3: resultOld value = 3New value = 6factorial (n=2) at k.cpp:1818          while(n--)(gdb) Continuing.Hardware watchpoint 2: nOld value = 2New value = 10x08048764 in factorial (n=1) at k.cpp:1818          while(n--)(gdb) Continuing.Hardware watchpoint 2: nOld value = 1New value = 00x08048764 in factorial (n=0) at k.cpp:1818          while(n--)(gdb) Continuing.Watchpoint 2 deleted because the program has left the block inwhich its expression is valid.Watchpoint 3 deleted because the program has left the block inwhich its expression is valid.0x08048705 in main () at k.cpp:99           long val=factorial(n);(gdb) p val$1 = 11476980(gdb) 
      
It can be seen that while, resulting in n out of bounds, fix
      
while(n>0) //doesn't let n reach 0{  result*=n;  n--;        //decrements only after the evaluation}
      
Some quick commands
      
l – listp – print print {variable}c – continues – stepb - break  break line_number/break [file_name]:line_number/break [file_name]:func_namer - runset  = 
        
         watch 
         ENTER: pressing enter key would execute the previously executed command again.
        
      
Differences between c/n/s
      

       
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. debug the PHP program
      
PHP code
      
       
Start Debugging and add breakpoints
[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 
        
         6       breakpoint     keep y   0x08069390 
         
          (gdb) 
         
        
Add a few breakpoints to test syntax: break [file_name]: func_name. here we can roughly see that echo print is not a function.
Then start debugging.
(gdb) run kk.php ( or set args ./kk.php && r)Starting program: /usr/bin/php kk.php[Thread debugging using libthread_db enabled]0Breakpoint 3, 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:44494449            if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "l", &num) == FAILURE) {(gdb) 
Here, let's take a look at what is returned by the zif_sleep function return_value.
(gdb) p *return_value$1 = {value = {lval = 1515870810, dval = 1.7838867517321418e+127, str = {val = 0x5a5a5a5a ,       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 ,     len = 1515870810}, ht = 0x5a5a5a5a, obj = {handle = 1515870810, handlers = 0x5a5a5a5a}}(gdb) p return_value->value->lval$3 = 1515870810
We can also use the built-in gdbinit for debugging.
(gdb) source /usr/local/src/php-5.5.23/.gdbinit(gdb) zbacktrace[0xb7fa1144] sleep(3) /code/kk.php:4
View the execution process of the current stack and PHP kernel
(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
View code segments
(gdb) l4444       Delay for a given number of seconds */4445    PHP_FUNCTION(sleep)4446    {4447            long num;44484449            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 44504445    PHP_FUNCTION(sleep)4446    {4447            long num;44484449            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_usleep4463    /* }}} */44644465    /* {{{ proto void usleep(int micro_seconds)4466       Delay for a given number of micro seconds */4467    PHP_FUNCTION(usleep)4468    {4469    #if HAVE_USLEEP4470            long num;44714472            if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "l", &num) == FAILURE) {
Continue execution
(gdb) n4452            if (num < 0) {(gdb) p num$6 = 3(gdb) n4457            RETURN_LONG(php_sleep(num));(gdb) n4462    }(gdb) nexecute_internal (execute_data_ptr=0xb7fa1144, fci=0x0, return_value_used=0) at /usr/local/src/php-5.5.23/Zend/zend_execute.c:14881488    }
To execute_internal, you can view a status of the current function.
(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"
View the current hashtable
(gdb) p *execute_data_ptr->symbol_table$16 = {nTableSize = 64, nTableMask = 63, nNumOfElements = 8, nNextFreeElement = 0, pInternalPointer = 0xb7fb924c,   pListHead = 0xb7fb924c, pListTail = 0xb7fbd228, arBuckets = 0xb7fb9120, pDestructor = 0x85bf06f <_zval_ptr_dtor_wrapper>,   persistent = 0 '\000', nApplyCount = 0 '\000', bApplyProtection = 1 '\001', inconsistent = 0}
After executing the output c, press enter to view the execution information of in_array.
(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 
        
         ,     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"
        
You can also add monitoring watch and set some debugging variables.
Other debugging tools include strace viewing system calls, ltrace viewing class library calls, and vld viewing opcode
　　
 
References
Http://www.cprogramming.com/gcc.html
Http://www.thegeekstuff.com/2010/03/debug-c-program-using-gdb/
Http://www.cprogramming.com/gdb.html
Http://www.laruence.com/2011/06/23/2057.html
Http://derickrethans.nl/what-is-php-doing.html
 
Example 1: GDB is a powerful program debugging tool for UNIX released by the GNU open-source organization. If you are running software on a UNIX platform ,...

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