gdb 调试PHP

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http://phpor.net/blog/post/997

PHP的代码包中提供了一个 .gdbinit 的gdb脚本文件，里面提供了20多个 gdb 的自定义命令，用于方便PHP的调试，下面举几个例子：
测试脚本a.php：

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<?php
$a = "AAA";
$b = "BBB";
test("phpor");
function test($name) {
        $m = "MMM";
        $n = "NNN";
        sleep(1);
        echo$name;
}

gdb 调试命令：
———————–
gdb php
set args a.php
break sleep
r
…
———————–

1. print_cvs 打印当前执行环境中已编译的PHP变量，如：

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(gdb)print_cvs
Compiledvariablescount:3
0=name
[0x9543f7c](refcount=2)string(5):"phpor"
1=m
[0x9543f98](refcount=1)string(3):"MMM"
2=n
[0x9543fb4](refcount=1)string(3):"NNN"
(gdb)

2. printzv 打印指定的PHP变量，需要指定地址，如：
(gdb) printzv 0x9543f98
[0x9543f98] (refcount=1) string(3): “MMM”
(gdb)

3. 打印PHP的函数调用栈，如：
(gdb) zbacktrace
[0x95770a4] sleep(1) /usr/home/junjie2/a.php:11
[0x9576fe0] test(“phpor”) /usr/home/junjie2/a.php:7
(gdb)

4. print_ft 打印函数表（ HashTable ）
(gdb) set $eg = executor_globals
(gdb) print $eg.function_table
$6 = (HashTable *) 0xa5bd450
(gdb) print_ft $eg.function_table
[0xa5bd450] {
“zend_version\0” => “zend_version”
“func_num_args\0” => “func_num_args”
“func_get_arg\0” => “func_get_arg”
“func_get_args\0” => “func_get_args”
“strlen\0” => “strlen”
“strcmp\0” => “strcmp”
“strncmp\0” => “strncmp”
“strcasecmp\0” => “strcasecmp”
“strncasecmp\0” => “strncasecmp”
“each\0” => “each”
…

学习：
1. 通过阅读 print_cvs 命令的实现，可以知道可以通过prev_execute_data来打印上一执行空间的PHP变量，如：
(gdb) printzv *executor_globals.current_execute_data->prev_execute_data->CVs[1]
[0x9543408] (refcount=1) string(3): “AAA”
(gdb) printzv *executor_globals.current_execute_data->prev_execute_data->CVs[2]
[0x95433ec] (refcount=1) string(3): “BBB”
(gdb)

2. 通过 op_array->vars 来找到对应的变量的名字
(gdb) printf “%s\n” ,executor_globals.current_execute_data->prev_execute_data->op_array->vars[1].name
a
(gdb) printf “%s\n” ,executor_globals.current_execute_data->prev_execute_data->op_array->vars[2].name
b

3. 修改了一下 print_cvs 命令，通过参数来获取每个执行空间的PHP的已编译变量

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define print_cvs
        ____executor_globals
        set $f = $eg.current_execute_data
        if $argc == 1
                set $j = 1
                while $j < $arg0 && $f.prev_execute_data != 0
                        set $f = $f.prev_execute_data
                        set $j = $j + 1
                end
        end
        set $p = $f.CVs
        set $c = $f.op_array.last_var
        set $v = $f.op_array.vars
        set $i = 0
        printf "Compiled variables count: %d\n", $c
        while $i < $c
                printf "%d = %s\n", $i, $v[$i].name
                if $p[$i] != 0
                        printzv *$p[$i]
                else
                        printf "*uninitialized*\n"
                end
                set $i = $i + 1
        end
end

使用方法：
———————
(gdb) zbacktrace #查看PHP的调用栈
[0x8ce2078] sleep(1) /usr/home/junjie2/a.php:9
[0x8ce1fe0] test(“phpor”) /usr/home/junjie2/a.php:5
(gdb) print_cvs #查看当前执行空间中的PHP变量
Compiled variables count: 3
0 = name
[0x8cae3d0] (refcount=2) string(5): “phpor”
1 = m
[0x8cae93c] (refcount=1) string(3): “MMM”
2 = n
[0x8cae958] (refcount=1) string(3): “NNN”
(gdb) print_cvs 2 # 查看指定执行空间中的PHP变量，这个参数给大了也没关系，最多打印最外层的PHP变量
Compiled variables count: 2
0 = a
[0x8cae408] (refcount=1) string(3): “AAA”
1 = b
[0x8cae3ec] (refcount=1) string(3): “BBB”
(gdb)
———————

4. 有时候需要借助环境变量，如：
(gdb) print_ft (HashTable *)0xa5bd450
A syntax error in expression, near `’.
(gdb) set $phpor=(HashTable *)0xa5bd450
(gdb) print_ft $phpor
[0xa5bd450] {
“zend_version\0” => “zend_version”
“func_num_args\0” => “func_num_args”
“func_get_arg\0” => “func_get_arg”
“func_get_args\0” => “func_get_args”
“strlen\0” => “strlen”
“strcmp\0” => “strcmp”
“strncmp\0” => “strncmp”

5. 打印指定的PHP变量

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defineprint_pval
    ____executor_globals
    set$p=$eg.current_execute_data.CVs
    set$c=$eg.current_execute_data.op_array.last_var
    set$v=$eg.current_execute_data.op_array.vars
    set$i=0
    set$name=$arg0
 
    #printf "search php var: %s c:%d\n", $name, $c
    while$i<$c
        #printf "name: %s\n", $name
        set$n=$v[$i].name
        # use strcmp but ==
        ifstrcmp($n,$name)==0
            if$p[$i]!=0
                printzv *$p[$i]
                # use loop_break but break
                loop_break
            end    
        end    
        #printf "i %d, %s\n", $i, $v[$i].name
        set$i=$i+1
    end
    if$i==$c
        printf"no found var named: %s\n",$name
    end
end

PHP的代码包中提供了一个 .gdbinit 的gdb脚本文件，里面提供了20多个 gdb 的自定义命令，用于方便PHP的调试，下面举几个例子：
测试脚本a.php：

1
2
3
4
5
6
7
8
9
10
<?php
$a = "AAA";
$b = "BBB";
test("phpor");
function test($name) {
        $m = "MMM";
        $n = "NNN";
        sleep(1);
        echo$name;
}

gdb 调试命令：
———————–
gdb php
set args a.php
break sleep
r
…
———————–

1. print_cvs 打印当前执行环境中已编译的PHP变量，如：

1
2
3
4
5
6
7
8
9
(gdb)print_cvs
Compiledvariablescount:3
0=name
[0x9543f7c](refcount=2)string(5):"phpor"
1=m
[0x9543f98](refcount=1)string(3):"MMM"
2=n
[0x9543fb4](refcount=1)string(3):"NNN"
(gdb)

2. printzv 打印指定的PHP变量，需要指定地址，如：
(gdb) printzv 0x9543f98
[0x9543f98] (refcount=1) string(3): “MMM”
(gdb)

3. 打印PHP的函数调用栈，如：
(gdb) zbacktrace
[0x95770a4] sleep(1) /usr/home/junjie2/a.php:11
[0x9576fe0] test(“phpor”) /usr/home/junjie2/a.php:7
(gdb)

4. print_ft 打印函数表（ HashTable ）
(gdb) set $eg = executor_globals
(gdb) print $eg.function_table
$6 = (HashTable *) 0xa5bd450
(gdb) print_ft $eg.function_table
[0xa5bd450] {
“zend_version\0” => “zend_version”
“func_num_args\0” => “func_num_args”
“func_get_arg\0” => “func_get_arg”
“func_get_args\0” => “func_get_args”
“strlen\0” => “strlen”
“strcmp\0” => “strcmp”
“strncmp\0” => “strncmp”
“strcasecmp\0” => “strcasecmp”
“strncasecmp\0” => “strncasecmp”
“each\0” => “each”
…

3. 修改了一下 print_cvs 命令，通过参数来获取每个执行空间的PHP的已编译变量

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define print_cvs
        ____executor_globals
        set $f = $eg.current_execute_data
        if $argc == 1
                set $j = 1
                while $j < $arg0 && $f.prev_execute_data != 0
                        set $f = $f.prev_execute_data
                        set $j = $j + 1
                end
        end
        set $p = $f.CVs
        set $c = $f.op_array.last_var
        set $v = $f.op_array.vars
        set $i = 0
        printf "Compiled variables count: %d\n", $c
        while $i < $c
                printf "%d = %s\n", $i, $v[$i].name
                if $p[$i] != 0
                        printzv *$p[$i]
                else
                        printf "*uninitialized*\n"
                end
                set $i = $i + 1
        end
end

使用方法：
———————
(gdb) zbacktrace #查看PHP的调用栈
[0x8ce2078] sleep(1) /usr/home/junjie2/a.php:9
[0x8ce1fe0] test(“phpor”) /usr/home/junjie2/a.php:5
(gdb) print_cvs #查看当前执行空间中的PHP变量
Compiled variables count: 3
0 = name
[0x8cae3d0] (refcount=2) string(5): “phpor”
1 = m
[0x8cae93c] (refcount=1) string(3): “MMM”
2 = n
[0x8cae958] (refcount=1) string(3): “NNN”
(gdb) print_cvs 2 # 查看指定执行空间中的PHP变量，这个参数给大了也没关系，最多打印最外层的PHP变量
Compiled variables count: 2
0 = a
[0x8cae408] (refcount=1) string(3): “AAA”
1 = b
[0x8cae3ec] (refcount=1) string(3): “BBB”
(gdb)
———————

5. 打印指定的PHP变量

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defineprint_pval
    ____executor_globals
    set$p=$eg.current_execute_data.CVs
    set$c=$eg.current_execute_data.op_array.last_var
    set$v=$eg.current_execute_data.op_array.vars
    set$i=0
    set$name=$arg0
 
    #printf "search php var: %s c:%d\n", $name, $c
    while$i<$c
        #printf "name: %s\n", $name
        set$n=$v[$i].name
        # use strcmp but ==
        ifstrcmp($n,$name)==0
            if$p[$i]!=0
                printzv *$p[$i]
                # use loop_break but break
                loop_break
            end    
        end    
        #printf "i %d, %s\n", $i, $v[$i].name
        set$i=$i+1
    end
    if$i==$c
        printf"no found var named: %s\n",$name
    end
end