PHP standard函数getcwd源码阅读小记

遇到了php-fpm register_shutdown_function()的一个bug：

echo "Expected:" . getcwd() . "<br>";

register_shutdown_function(function () {
    echo "In shutdown function:" . getcwd() . "<br>";
});

php-fpm输出如下

Expected:/var/www/html/test
In shutdown function:/

在cli模式下输出正常

Expected:/var/www/html/test<br>In shutdown function:/var/www/html/test<br>

去翻翻源码，找到getcwd的定义
函数定义的位置在：ext/standard/dir.c的364行

PHP_FUNCTION(getcwd)
{
    char path[MAXPATHLEN];
    char *ret=NULL;

    if (zend_parse_parameters_none() == FAILURE) {
        return;
    }

#if HAVE_GETCWD
    ret = VCWD_GETCWD(path, MAXPATHLEN);  //这里调用ZEND的方法，获取当前工作目录
#elif HAVE_GETWD
    ret = VCWD_GETWD(path);
#endif

    if (ret) {
        RETURN_STRING(path);
    } else {
        RETURN_FALSE;
    }
}

可见，此方法其实是关联到一个ZEND方法VCWD_GETWD()

#define VCWD_GETCWD(buff, size) virtual_getcwd(buff, size)

PHP内核定义了十分之多的宏，所以需要找到真正定义还得费点劲
最终找到真正定义位置，在Zend\zend_virtual_cwd.h

CWD_API char *virtual_getcwd_ex(size_t *length)
{
    cwd_state *state;

    state = &CWDG(cwd);   //获取全局的virtual_getcwd 

    if (state->cwd_length == 0) {
        char *retval;

        *length = 1;
        retval = (char *) emalloc(2);
        if (retval == NULL) {
            return NULL;
        }
        retval[0] = DEFAULT_SLASH;
        retval[1] = '\0';
        return retval;
    }

#ifdef ZEND_WIN32
    /* If we have something like C: */
    if (state->cwd_length == 2 && state->cwd[state->cwd_length-1] == ':') {
        char *retval;

        *length = state->cwd_length+1;
        retval = (char *) emalloc(*length+1);
        if (retval == NULL) {
            return NULL;
        }
        memcpy(retval, state->cwd, *length);
        retval[0] = toupper(retval[0]);
        retval[*length-1] = DEFAULT_SLASH;
        retval[*length] = '\0';
        return retval;
    }
#endif
    if (!state->cwd) {
        *length = 0;
        return NULL;
    }

    *length = state->cwd_length;
    return estrdup(state->cwd);
}

CWD_API char *virtual_getcwd(char *buf, size_t size)
{
    size_t length;
    char *cwd;

    cwd = virtual_getcwd_ex(&length);    // 真正获取cwd的地方

    if (buf == NULL) {
        return cwd;
    }
    if (length > size-1) {
        efree(cwd);
        errno = ERANGE; /* Is this OK? */
        return NULL;
    }
    if (!cwd) {
        return NULL;
    }
    memcpy(buf, cwd, length+1);   //复制内容
    efree(cwd);  // 防止内存泄漏
    return buf;
}

找到CWDG定义

#ifdef ZTS
extern ts_rsrc_id cwd_globals_id;
# define CWDG(v) ZEND_TSRMG(cwd_globals_id, virtual_cwd_globals *, v)
#else
extern virtual_cwd_globals cwd_globals;
# define CWDG(v) (cwd_globals.v)
#endif

可以看到，方法是获取一个全局变量，cwd_globals

根据上面源码的阅读，可以进一步推测应该是shutdown_function的时候cwd_globals已经被修改了
这种情况只发生在php-fpm模式下，cli未发现

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