stdout引发的curl 302跳转 crash

重现步骤：

• 0、开发环境：Windows 7 SP1 64bit, VS2008 SP1
• 1、进程中修改了stdout这个句柄的值：调用了prinft和cout都会修改stdout，TRACE不会修改stdout
• 2、使用curl请求一个会跳转的url（HTTP 跳转的话curl会收到包含302的response header）
• 3、crash

问题影响

• curl版本7.21.7和7.28.1都有这个问题

问题原因和解决方案

很可能是curl的一个bug，目前没有找到完美的解决方案，只能在进程中不要使用printf和cout

代码

如果你调用了printf或者cout，你会发现在curl初始化的时候，调用了这个代码，这个时候的stdout已经被修改了

// code block from url.c
/*
 * Initialize the UserDefined fields within a SessionHandle.
 * This may be safely called on a new or existing SessionHandle.
 */
CURLcode Curl_init_userdefined(struct UserDefined *set)
{
  CURLcode res = CURLE_OK;

  set->out = stdout; /* default output to stdout */ // linyehui:这个set.out有问题
  set->in  = stdin;  /* default input from stdin */
  set->err  = stderr;  /* default stderr to stderr */

实际crash的地方：

// code block from sendf.c

/* Curl_client_write() sends data to the write callback(s)

   The bit pattern defines to what "streams" to write to. Body and/or header.
   The defines are in sendf.h of course.

   If CURL_DO_LINEEND_CONV is enabled, data is converted IN PLACE to the
   local character encoding.  This is a problem and should be changed in
   the future to leave the original data alone.
 */
CURLcode Curl_client_write(struct connectdata *conn,
                           int type,
                           char *ptr,
                           size_t len)
{
    // ...  
    /* If the previous block of data ended with CR and this block of data is
       just a NL, then the length might be zero */
    if(len) {
      wrote = data->set.fwrite_func(ptr, 1, len, data->set.out); // linyehui:这个set.out有问题
    }
    else {
      wrote = len;
    }

// ...

呵呵……