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        2. 深入了解PHP:用gdb調試源碼

          來源:php中文網 | 2022-12-28 17:51:11 |

          本篇文章給大家帶來了關于PHP的相關知識,其中主要介紹了關于使用gdb調試源碼的相關內容,下面一起來看一下,希望對大家有幫助。

          推薦學習:《PHP視頻教程》

          php編譯時有一個debug模式,這個模式會關閉內存優化,提示內存泄露,屏蔽調用棧優化可以讓我們看到完整的php c層面的調用棧。

          通常我會編譯兩個php版(一個正常,一個打開debug)在不同的目錄,通過export決定使用哪個。


          (資料圖片)

          通過php-config命令可以看到configure-options,修改其中的prefix 和 with-config-file-path 到新的目錄,然后添加--enable-debug 命令

          yongkbmaster ?  ~ php-configUsage: /data/env/runtime/php-7.1.33-debug/bin/php-config [OPTION]Options:  --prefix            [/data/env/runtime/php-7.1.33-debug]  --includes          [-I/data/env/runtime/php-7.1.33-debug/include/php -I/data/env/runtime/php-7.1.33-debug/include/php/main -I/data/env/runtime/php-7.1.33-debug/include/php/TSRM -I/data/env/runtime/php-7.1.33-debug/include/php/Zend -I/data/env/runtime/php-7.1.33-debug/include/php/ext -I/data/env/runtime/php-7.1.33-debug/include/php/ext/date/lib]  --ldflags           []  --libs              [-lcrypt   -lz -lexslt -lresolv -lcrypt -lrt -lldap -llber -lpng -lz -ljpeg -lcurl -lbz2 -lz -lrt -lm -ldl -lnsl  -lxml2 -lz -lm -ldl -lgssapi_krb5 -lkrb5 -lk5crypto -lcom_err -lssl -lcrypto -lcurl -lxml2 -lz -lm -ldl -lfreetype -lxml2 -lz -lm -ldl -lxml2 -lz -lm -ldl -lcrypt -lxml2 -lz -lm -ldl -lxml2 -lz -lm -ldl -lxml2 -lz -lm -ldl -lxml2 -lz -lm -ldl -lxslt -lxml2 -lz -ldl -lm -lssl -lcrypto -lcrypt ]  --extension-dir     [/data/env/runtime/php-7.1.33-debug/lib/php/extensions/debug-non-zts-20160303]  --include-dir       [/data/env/runtime/php-7.1.33-debug/include/php]  --man-dir           [/data/env/runtime/php-7.1.33-debug/php/man]  --php-binary        [/data/env/runtime/php-7.1.33-debug/bin/php]  --php-sapis         [ cli fpm phpdbg cgi]  --configure-options [--prefix=/data/env/runtime/php-7.1.33-debug --enable-debug --enable-phpdbg-debug --with-config-file-path=/data/env/runtime/php-7.1.33-debug/etc --with-curl --with-freetype-dir --with-gd --with-gettext --with-iconv-dir --with-kerberos --with-libdir=lib64 --with-libxml-dir --with-mysqli --with-openssl --with-pcre-regex --with-pdo-mysql --with-pdo-sqlite --with-pear --with-png-dir --with-jpeg-dir --with-xmlrpc --with-xsl --with-zlib --with-bz2 --with-mhash --enable-fpm --enable-bcmath --enable-libxml --enable-inline-optimization --enable-gd-native-ttf --enable-mbregex --enable-mbstring --enable-opcache --enable-pcntl --enable-shmop --enable-soap --enable-sockets --enable-sysvsem --enable-sysvshm --enable-xml --enable-zip --with-ldap]  --version           [7.1.33]  --vernum            [70133]

          修改之后大概是這樣子,然后編譯安裝 就可以得到debug版本了

          --prefix=/data/env/runtime/php-7.1.33-debug --enable-debug --enable-phpdbg-debug --with-config-file-path=/data/env/runtime/php-7.1.33-debug/etc --with-curl --with-freetype-dir --with-gd --with-gettext --with-iconv-dir --with-kerberos --with-libdir=lib64 --with-libxml-dir --with-mysqli --with-openssl --with-pcre-regex --with-pdo-mysql --with-pdo-sqlite --with-pear --with-png-dir --with-jpeg-dir --with-xmlrpc --with-xsl --with-zlib --with-bz2 --with-mhash --enable-fpm --enable-bcmath --enable-libxml --enable-inline-optimization --enable-gd-native-ttf --enable-mbregex --enable-mbstring --enable-opcache --enable-pcntl --enable-shmop --enable-soap --enable-sockets --enable-sysvsem --enable-sysvshm --enable-xml --enable-zip --with-ldap

          php --version中看到DEBUG 就可以了

          yongkbmaster ?  ~ /data/env/runtime/php-7.1.33-debug/bin/php --versionPHP 7.1.33 (cli) (built: Dec 29 2020 19:16:50) ( NTS DEBUG )Copyright (c) 1997-2018 The PHP GroupZend Engine v3.1.0, Copyright (c) 1998-2018 Zend Technologie

          注意:Debug版本的擴展需要再次編譯安裝,不能拷貝正常版本的so,安裝方式和普通擴展一致,一般不需要開額外的debug參數。如果你需要調試擴展比如swoole你需要設置擴展的debug參數,可以參考擴展的./configure文件說明。

          gdb使用

          這里簡單介紹一下gdb的基本使用,更詳細的使用方法可以自行google。

          啟動gdb

          捕獲進程

          gdb -p {pid}

          run 方法啟動

          gdb phprun test3.php

          通過core 文件

          gdb -c core.8451

          斷點

          break n :在第n行處設置斷點(可以帶上代碼路徑和代碼名稱)

          //注意:這里只能斷點c代碼,php文件不行的,var.c:201在php-7.1.33是var_dump的入口break var.c:201

          b fn1 if a>b:條件斷點設置

          break func(break縮寫為b):在函數func()的入口處設置斷點

          //大部分php的方法在c層面的方法名都是zif_ + php方法名。 例如 var_dump 在c的方法名叫zif_var_dumpbreak zif_var_dump

          delete 斷點號n:刪除第n個斷點

          disable 斷點號n:暫停第n個斷點

          enable 斷點號n:開啟第n個斷點

          clear 行號n:清除第n行的斷點

          info b (info breakpoints) :顯示當前程序的斷點設置情況

          delete breakpoints:清除所有斷點

          其他

          list (簡寫 l) ,其作用就是列出程序的源代碼,默認每次顯示10行。

          list 行號:將顯示當前文件以“行號”為中心的前后10行代碼,

          print a:將顯示 a 的值

          continue (簡寫c ):繼續執行,到下一個斷點處(或運行結束)。設置斷點后需要按這個。

          next (簡寫n):當前函數,下一行

          step (簡寫s):跳入函數內部

          where/bt :當前運行的堆棧列表;

          php gdb 小工具

          這里就是本文的重點了php為gdb提供了一組小工具,在源代碼目錄下的.gdbinit文件中,它可以幫助我們更好的gdb php源代碼。

          準備

          為了更好的演示,我這里準備一個php文件。

          <?phpconst A = "test const";const B = "test const B";class B {        public $a = "test";        public function funB() {                var_dump("test funB");        }}class C extends B {        public function funC() {                var_dump("test funC");        }}$a = "test";$b = ["a1" => 1, "a2" => 2];$c = new B();$d = [A, B];$e = new C();$f = $b;var_dump($a, $b, $c, $d, $e, $f);get_object_vars($e);

          啟動gdb,設置2個斷點。

          gdb php //注意這里要用debug版本的(gdb) break var.c:211Breakpoint 1 at 0x76e717: file /data/env/runtime/php-7.1.33-src/ext/standard/var.c, line 211.(gdb) break zend_object_handlers.c:492Breakpoint 2 at 0x86ce9d: file /data/env/runtime/php-7.1.33-src/Zend/zend_object_handlers.c, line 492.(gdb) r test4.php

          然后載入小工具

          source /data/env/runtime/php-7.1.33-src/.gdbinit

          使用

          zbacktrace 顯示當前的php調用棧

          (gdb) zbacktrace[0x7ffff1614200] var_dump("test", array(2)[0x7ffff1614260], object[0x7ffff1614270], array(2)[0x7ffff1614280], object[0x7ffff1614290], array(2)[0x7ffff16142a0]) [internal function][0x7ffff1614030] (main) /root/test4.php:26

          dump_bt 查看當前調用棧 和 zbacktrace 類似

          (gdb) dump_bt executor_globals.current_execute_data[0x7ffff1614200] var_dump("test", array(2)[0x7ffff1614260], object[0x7ffff1614270], array(2)[0x7ffff1614280], object[0x7ffff1614290], array(2)[0x7ffff16142a0]) [internal function][0x7ffff1614030] (main) /root/test4.php:26

          printzv 輸出zend value 的情況

          (gdb) printzv &args[0][0x7ffff1614250] (refcount=0) string: test

          print_global_vars 輸出全局變量

          (gdb) print_global_varsHash(13)[0x11bf0d0]: {  [0] _GET => [0x7ffff1657100] (refcount=2) array:  [1] _POST => [0x7ffff1657120] (refcount=2) array:  [2] _COOKIE => [0x7ffff1657140] (refcount=2) array:  [3] _FILES => [0x7ffff1657160] (refcount=2) array:  [4] argv => [0x7ffff1657180] (refcount=2) array:  [5] argc => [0x7ffff16571a0] long: 1  [6] _SERVER => [0x7ffff16571c0] (refcount=2) array:  [7] a => [0x7ffff16571e0] indirect: [0x7ffff1613080] (refcount=0) string: test  [8] b => [0x7ffff1657200] indirect: [0x7ffff1613090] (refcount=5) array:  [9] c => [0x7ffff1657220] indirect: [0x7ffff16130a0] (refcount=2) object(B) #2  [10] d => [0x7ffff1657240] indirect: [0x7ffff16130b0] (refcount=2) array:  [11] e => [0x7ffff1657260] indirect: [0x7ffff16130c0] (refcount=2) object(C) #3  [12] f => [0x7ffff1657280] indirect: [0x7ffff16130d0] (refcount=5) array:

          print_const_table 輸出定義的常量

          (gdb) print_const_table executor_globals.zend_constants[0x14e8380] {  Hash(2340)[0x14e8380]: {    [0] E_ERROR => [0x14fd660] long: 1    [1] E_RECOVERABLE_ERROR => [0x14fe8a0] long: 4096    [2] E_WARNING => [0x14fe900] long: 2    [3] E_PARSE => [0x14fe960] long: 4    [4] E_NOTICE => [0x14fe9c0] long: 8    [5] E_STRICT => [0x14fea20] long: 2048    [6] E_DEPRECATED => [0x14fea80] long: 8192    [7] E_CORE_ERROR => [0x14feae0] long: 16    [8] E_CORE_WARNING => [0x14feb40] long: 32    [9] E_COMPILE_ERROR => [0x14feba0] long: 64    [10] E_COMPILE_WARNING => [0x14fec10] long: 128    [11] E_USER_ERROR => [0x14fec70] long: 256    [12] E_USER_WARNING => [0x14fecd0] long: 512    [13] E_USER_NOTICE => [0x14fed30] long: 1024    [14] E_USER_DEPRECATED => [0x14feda0] long: 16384    [15] E_ALL => [0x14fee00] long: 32767    [16] DEBUG_BACKTRACE_PROVIDE_OBJECT => [0x14fee70] long: 1    [17] DEBUG_BACKTRACE_IGNORE_ARGS => [0x14feee0] long: 2    [18] true => [0x14fef70] bool: true    [19] false => [0x14ff000] bool: false    [20] ZEND_THREAD_SAFE => [0x14ff070] bool: false    [21] ZEND_DEBUG_BUILD => [0x14ff0e0] bool: true    [22] null => [0x14ff170] NULL    [23] PHP_VERSION => [0x1500380] (refcount=1) string: 7.1.33 ......

          print_zstr 輸出zend string

          (gdb) print_zstr args[0]string(4) "test"(gdb) print_zstr args[0] 2string(4) "te..."(gdb) print_zstr args[0] 4string(4) "test"

          print_cvs 打印已編譯的變量及其值 它需要傳入一個 zend_execute_data 類型的值??梢韵萣t看一下調用棧。

          (gdb) bt //這里看到 #2 層這里是 zend_vm_execute 的執行入口,這里有zend_execute_data 類型的值。#0  zif_var_dump (execute_data=0x7ffff1614120, return_value=0x7fffffffa9b0) at /data/env/runtime/php-7.1.33-src/ext/standard/var.c:209#1  0x0000000000ab08d4 in ZEND_DO_ICALL_SPEC_RETVAL_UNUSED_HANDLER () at /data/env/runtime/php-7.1.33-src/Zend/zend_vm_execute.h:628#2  0x0000000000ab01c3 in execute_ex (ex=0x7ffff1614030) at /data/env/runtime/php-7.1.33-src/Zend/zend_vm_execute.h:429#3  0x0000000000ab02d5 in zend_execute (op_array=0x7ffff1672d00, return_value=0x0) at /data/env/runtime/php-7.1.33-src/Zend/zend_vm_execute.h:474#4  0x0000000000a510f9 in zend_execute_scripts (type=8, retval=0x0, file_count=3) at /data/env/runtime/php-7.1.33-src/Zend/zend.c:1482#5  0x00000000009c02f4 in php_execute_script (primary_file=0x7fffffffdf30) at /data/env/runtime/php-7.1.33-src/main/main.c:2577#6  0x0000000000b31387 in do_cli (argc=2, argv=0x14e7f30) at /data/env/runtime/php-7.1.33-src/sapi/cli/php_cli.c:993#7  0x0000000000b32346 in main (argc=2, argv=0x14e7f30) at /data/env/runtime/php-7.1.33-src/sapi/cli/php_cli.c:1381(gdb) f 2 //跳到#2 這一層#2  0x0000000000ab01c3 in execute_ex (ex=0x7ffff1614030) at /data/env/runtime/php-7.1.33-src/Zend/zend_vm_execute.h:429429                     ((opcode_handler_t)OPLINE->handler)(ZEND_OPCODE_HANDLER_ARGS_PASSTHRU);(gdb) print_cvs ex //輸出Compiled variables count: 6[0] "a"[0x7ffff1614080] (refcount=0) string: test[1] "b"[0x7ffff1614090] (refcount=5) array:     Hash(2)[0x7ffff170e300]: {      [0] a1 => [0x7ffff1793e20] long: 1      [1] a2 => [0x7ffff1793e40] long: 2}[2] "c"[0x7ffff16140a0] (refcount=2) object(B) #2Properties     Hash(1)[0x7ffff170e480]: {      [0] a => [0x7ffff1793f60] indirect: [0x7ffff170e388] (refcount=4) string: test}[3] "d"[0x7ffff16140b0] (refcount=2) array:     Packed(2)[0x7ffff170e3c0]: {      [0] 0 => [0x7ffff1793688] (refcount=1) string: test const      [1] 1 => [0x7ffff17936a8] (refcount=1) string: test const B}[4] "e"[0x7ffff16140c0] (refcount=2) object(C) #3Properties     Hash(1)[0x7ffff170e4e0]: {      [0] a => [0x7ffff17940a0] indirect: [0x7ffff170e448] (refcount=4) string: test}[5] "f"[0x7ffff16140d0] (refcount=5) array:     Hash(2)[0x7ffff170e300]: {      [0] a1 => [0x7ffff1793e20] long: 1      [1] a2 => [0x7ffff1793e40] long: 2}

          print_ht 輸出HashTable, HashTable是php底層一個重要的數據結構是php array的實現方式,你可以理解為是C層面的php array,在php源碼中也大量使用HashTable存儲各類k v結構或數組結構。

          (gdb) print_ht args[1].valueHash(2)[0x7ffff170e300]: {  [0] a1 => [0x7ffff1793e20] long: 1  [1] a2 => [0x7ffff1793e40] long: 2}(gdb) print_ht args[3].valuePacked(2)[0x7ffff170e3c0]: {  [0] 0 => [0x7ffff1793688] (refcount=1) string: test const  [1] 1 => [0x7ffff17936a8] (refcount=1) string: test const B}

          print_htptr 和 print_ht 類似,它輸出的是zval的地址不是zval的值

          (gdb) print_htptr args[1].valueHash(2)[0x7ffff170e300]: {  [0] a1 => 0x7ffff1793e20  [1] a2 => 0x7ffff1793e40}

          print_htstr 和 print_ht 類似,只是HashTable中存的不是zval 而是c char,但是這種情況在源碼中好像很少見了,大部分存字符串的情況會直接用zend string,我找了一圈在 php_cli_server_mime_type_ctor 有一處使用

          (gdb) print_htstr &server->extension_mime_typesHash(2)[0x11b9228]: {  [0] ez => application/andrew-inset  [1] aw => application/applixware}

          print_ft 和 print_ht 類似,只是HashTable中存的是 zend_function 的地址

          (gdb) print_ft &args[2].value.obj.ce.function_tableHash(1)[0x7ffff1783210]: {  [0] funb => "funB"}

          print_inh 輸出class相關信息

          (gdb) print_inh &args[4].value.obj.ceclass C extends B { class B { }}

          print_pi 輸出對象中屬性相關信息,它需要傳入一個zend_property_info類型的地址,在zend_object_handlers.c:492中有使用,php中可以用get_object_vars($e) 觸發。

          (gdb) cContinuing.Breakpoint 2, zend_check_property_access (zobj=0x7ffff170e420, prop_info_name=0x7ffff173c2c0) at /data/env/runtime/php-7.1.33-src/Zend/zend_object_handlers.c:492492             zend_string_release(member);(gdb) print_pi property_info[0x7ffff17833c8] {    offset = 0x28    ce = [0x7ffff17831d0] B    flags = 0x100 (ZEND_ACC_PUBLIC)    name  = string(1) "a"    default value: [0x7ffff17690c0] (refcount=4) string: test}

          推薦學習:《PHP視頻教程》

          以上就是深入了解PHP:用gdb調試源碼的詳細內容,更多請關注php中文網其它相關文章!

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