gdb 调试PHP

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：

<?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：

(gdb) print_cvs
Compiled variables count: 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

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

define print_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 ==
if strcmp($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

gdb 调试PHP