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【docker+gdb】调试 PHP 源码,看 strval 函数 C 完成【php教程】

作者:搜搜PHP网发布时间:2019-11-26分类:PHP教程浏览:81


导读:phpstrval函数的作用很简朴,就是你给他一个值,他给你返回字符串范例。算是一个比较简朴的函数了,我们来经由过程gdb来一探终究。经由过程本文,你能够窥伺下...
php strval 函数的作用很简朴,就是你给他一个值,他给你返回字符串范例。

算是一个比较简朴的函数了,我们来经由过程 gdb 来一探终究。

经由过程本文,你能够窥伺下

● gdb 的简朴运用

● gdb gui 形式初探

● 看看日常平凡写的 PHP 代码在 C 言语里的模样

● 对运用 gdb 调试 php 代码有个开端相识

● 对了,文末有一些截图,不要错过

采购食材

● 电脑一台

● docker 和 docker-compose

gdb 也好, PHP 也好,都打包成 docker 镜像啦,开袋即食,甚好。

备菜环节

1、运用 docker 拉取环境

# 拉取准备好的环境
git clone https://github.com/rovast/docker-examples.git
# 进入项目
cd docker-examples/gdb-php-src/
# 启动,会阅历一个冗长又不太冗长的守候,看你网速
docker-compose up -d

关于容器内的环境,人人能够看看 dockerfile

实在很简朴,就是基于 gcc 官方镜像构建,然后增加了 vim gdb,而且下载了 php7.0.0 的源码,根据 debug 参数举行编译

显现以下

Creating network "gdb-php-src_default" with the default driver
Creating gdb-php-src ... done

2、进入容器

docker exec -it gdb-php-src bash
### 显现下面的东西,示意你已进入到容器内了 ####
root@71a98d1bc1a6:/home#

我们看看容器内的环境(php 以及 gdb)

### 我们在容器内看看环境
root@71a98d1bc1a6:/home# ls
php-7.0.0  start.md
root@71a98d1bc1a6:/home# gdb -v
GNU gdb (Debian 7.12-6) 7.12.0.20161007-git
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".
root@71a98d1bc1a6:/home# php -v
PHP 7.0.0 (cli) (built: Apr 17 2019 13:33:30) ( NTS DEBUG )
Copyright (c) 1997-2015 The PHP Group
Zend Engine v3.0.0, Copyright (c) 1998-2015 Zend Technologies
root@71a98d1bc1a6:/home#

开仗(请在容器内操纵)

1、新建测试文件

root@71a98d1bc1a6:/home# vi test.php

输入以下内容

<?php
strval(1234);

这个文件干的事情就比较简朴了,就是把 -1234 [整形] 转换为 -1234 [字符串]

2、最先调试,进入 gdb

接下来车速较快,列位按步骤跟上

输入 gdb php,最先调试

root@71a98d1bc1a6:/home# gdb php
GNU gdb (Debian 7.12-6) 7.12.0.20161007-git
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 php...done.
(gdb)

3、打一些断点(敲敕令时能够用 tab 补全)

(gdb) b zend_long_to_str
Breakpoint 1 at 0x810423: file /home/php-7.0.0/Zend/zend_operators.c, line 2743.
(gdb) b zend_print_ulong_to_buf
Breakpoint 2 at 0x5f387b: zend_print_ulong_to_buf. (13 locations)
(gdb)

这里在症结函数 zend_long_to_str 和 zend_print_ulong_to_buf 打了断点。

b 在 gdb 中是 breakpoint 缩写,背面能够加函数名,或许当前文件的行号都是能够的

4、实行,检察断点值

(gdb) r test.php # 实行我们适才的谁人 PHP 文件
Starting program: /usr/local/bin/php test.php
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
warning: File "/usr/local/lib64/libstdc++.so.6.0.25-gdb.py" auto-loading has been declined by your `auto-load safe-path' set to "$debugdir:$datadir/auto-load".
To enable execution of this file add
   add-auto-load-safe-path /usr/local/lib64/libstdc++.so.6.0.25-gdb.py
line to your configuration file "/root/.gdbinit".
To completely disable this security protection add
   set auto-load safe-path /
line to your configuration file "/root/.gdbinit".
For more information about this security protection see the
"Auto-loading safe path" section in the GDB manual.  E.g., run from the shell:
   info "(gdb)Auto-loading safe path"
Breakpoint 1, zend_long_to_str (num=-1234) at /home/php-7.0.0/Zend/zend_operators.c:2743
2743      char *res = zend_print_long_to_buf(buf + sizeof(buf) - 1, num);
(gdb)

看的彷佛不明了嘛, ctrl + x 后再按 a 进入 gui 形式看看

 ┌──/home/php-7.0.0/Zend/zend_operators.c────────────────────────────────────────────────────────────────────────────────────────────────┐
   │2731    ZEND_API void ZEND_FASTCALL zend_locale_sprintf_double(zval *op ZEND_FILE_LINE_DC) /* {{{ */                                   │
   │2732    {                                                                                                                              │
   │2733            zend_string *str;                                                                                                      │
   │2734                                                                                                                                   │
   │2735            str = zend_strpprintf(0, "%.*G", (int) EG(precision), (double)Z_DVAL_P(op));                                           │
   │2736            ZVAL_NEW_STR(op, str);                                                                                                 │
   │2737    }                                                                                                                              │
   │2738    /* }}} */                                                                                                                      │
   │2739                                                                                                                                   │
   │2740    ZEND_API zend_string* ZEND_FASTCALL zend_long_to_str(zend_long num) /* {{{ */                                                  │
   │2741    {                                                                                                                              │
   │2742            char buf[MAX_LENGTH_OF_LONG + 1];                                                                                      │
B+>│2743            char *res = zend_print_long_to_buf(buf + sizeof(buf) - 1, num);                                                        │
   │2744            return zend_string_init(res, buf + sizeof(buf) - 1 - res, 0);                                                          │
   │2745    }                                                                                                                              │
   │2746    /* }}} */                                                                                                                      │
   │2747                                                                                                                                   │
   │2748    ZEND_API zend_uchar ZEND_FASTCALL is_numeric_str_function(const zend_string *str, zend_long *lval, double *dval) /* {{{ */ {   │
   │2749        return is_numeric_string_ex(ZSTR_VAL(str), ZSTR_LEN(str), lval, dval, -1, NULL);                                           │
   │2750    }                                                                                                                              │
   │2751    /* }}} */                                                                                                                      │
   │2752                                                                                                                                   │
   │2753    ZEND_API zend_uchar ZEND_FASTCALL _is_numeric_string_ex(const char *str, size_t length, zend_long *lval, double *dval, int allo│
   │2754    {                                                                                                                              │
   │2755            const char *ptr;                                                                                                       │
   │2756            int digits = 0, dp_or_e = 0;                                                                                           │
   │2757            double local_dval = 0.0;                                                                                               │
   └───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
multi-thre Thread 0x7ffff7fe37 In: zend_long_to_str                                                                      L2743 PC: 0x810423
(gdb)

有点意义了,函数在 2743 行断住了,我们来看看 num 的值

(gdb) p num
$1 = -1234
(gdb)

对嘛,这个就是我们要处置惩罚的值,我们全速运转到 zend_print_long_to_buf 里看看

(gdb) c
Continuing.

显现以下

(gdb) c
  ┌──/home/php-7.0.0/Zend/zend_operators.h────────────────────────────────────────────────────────────────────────────────────────────────┐
   │781             else                                                                                                   \               │
   │782             ZEND_TRY_BINARY_OP2_OBJECT_OPERATION(opcode)                                                                           │
   │783                                                                                                                                    │
   │784     #define ZEND_TRY_UNARY_OBJECT_OPERATION(opcode)                                                            \                   │
   │785             if (UNEXPECTED(Z_TYPE_P(op1) == IS_OBJECT)                                                             \               │
   │786                     && UNEXPECTED(Z_OBJ_HANDLER_P(op1, do_operation))                                                  \           │
   │787                     && EXPECTED(SUCCESS == Z_OBJ_HANDLER_P(op1, do_operation)(opcode, result, op1, NULL))) { \                     │
   │788                     return SUCCESS;                                                                                    \           │
   │789             }                                                                                                                      │
   │790                                                                                                                                    │
   │791     /* buf points to the END of the buffer */                                                                                      │
   │792     static zend_always_inline char *zend_print_ulong_to_buf(char *buf, zend_ulong num) {                                           │
B+>│793             *buf = '\0';                                                                                                           │
   │794             do {                                                                                                                   │
   │795                     *--buf = (char) (num % 10) + '0';                                                                              │
   │796                     num /= 10;                                                                                                     │
   │797             } while (num > 0);                                                                                                     │
   │798             return buf;                                                                                                            │
   │799     }                                                                                                                              │
   │800                                                                                                                                    │
   │801     /* buf points to the END of the buffer */                                                                                      │
   │802     static zend_always_inline char *zend_print_long_to_buf(char *buf, zend_long num) {                                             │
   │803             if (num < 0) {                                                                                                         │
   │804                 char *result = zend_print_ulong_to_buf(buf, ~((zend_ulong) num) + 1);                                              │
   │805                 *--result = '-';                                                                                                   │
   │806                     return result;                                                                                                 │
   │807             } else {                                                                                                               │
   └───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
multi-thre Thread 0x7ffff7fe37 In: zend_print_ulong_to_buf                                                               L793  PC: 0x8041fd

接下来,我们来举行一些单步调试,看看内存里的值

Breakpoint 1, zend_long_to_str (num=-1234) at /home/php-7.0.0/Zend/zend_operators.c:2743
(gdb) c  #-------------> 示意继承实行
Continuing.
Breakpoint 2, zend_print_ulong_to_buf (buf=0x7fffffffafe4 "", num=1234) at /home/php-7.0.0/Zend/zend_operators.h:793
(gdb) b 798  #-------------> 798行打个断点
Breakpoint 6 at 0x5f38e2: /home/php-7.0.0/Zend/zend_operators.h:798. (13 locations)
(gdb) c 
Continuing.
Breakpoint 6, zend_print_ulong_to_buf (buf=0x7fffffffafe0 "1234", num=0) at /home/php-7.0.0/Zend/zend_operators.h:798
(gdb) p buf  #-------------> 检察 buf 的值
$2 = 0x7fffffffafe0 "1234"
(gdb) x/10c buf  #-------------> 检察 buf 位置最先,一连 10 个以 char 为单元的内存值
0x7fffffffafe0: 49 '1'  50 '2'  51 '3'  52 '4'  0 '\000'        0 '\000'        0 '\000'        0 '\000'
0x7fffffffafe8: 0 '\000'        65 'A'
(gdb)

我们看到,函数返回的 buf 是字符串范例的 '1234'

我们看看函数 zend_print_ulong_to_buf,实在就是从高位到低位,按个取模(除以 10,取整数部份),然后塞到 buf 缓冲区。

比较有意义的是,buf 初始化的时刻指向的是缓冲区的末端,所以添补的时刻高位在末了,然后逐渐往前添补低位。

末了完毕的时刻,buf 就是我们须要的字符串类容了

消化

实在,本文就是运用 gdb 调试了 PHP 代码,仅此而已。

更多的是给人人供应了一个直接上手玩玩的时机,你所须要的只是个 docker,然后动着手调试,很有意义。

着手尝尝吧,以至,去看 C 源码吧!

附录

手摸手带你看 strval 函数 C 完成

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