c/c++ curl smtp 发送邮件太长导致段错误的问题

在Linux下，使用 libcurl 库发送邮件，当邮件长度超过16000字节时（具体应该为 16000 ~ 17000之间），

 执行到 curl_easy_perform(curl); 会发生段错误 Segmentation fault

下面看一下 curl 提供的 smtp 示例：

#include <stdio.h>#include <string.h>#include <curl/curl.h>/* This is a simple example showing how to send mail using libcurl's SMTP * capabilities. For an example of using the multi interface please see * smtp-multi.c. * * Note that this example requires libcurl 7.20.0 or above. */#define FROM    "<[e-mail]>"#define TO      "<[e-mail]>"#define CC      "<[e-mail]>"static const char *payload_text[] = {  "Date: Mon, 29 Nov 2010 21:54:29 +1100\r\n",  "To: " TO "\r\n",  "From: " FROM "(Example User)\r\n",  "Cc: " CC "(Another example User)\r\n",  "Message-ID: <dcd7cb36-11db-487a-9f3a-e652a9458efd@"  "rfcpedant.example.org>\r\n",  "Subject: SMTP example message\r\n",  "\r\n", /* empty line to divide headers from body, see RFC5322 */  "The body of the message starts here.\r\n",  "\r\n",  "It could be a lot of lines, could be MIME encoded, whatever.\r\n",  "Check RFC5322.\r\n",  NULL};struct upload_status {  int lines_read;};static size_t payload_source(void *ptr, size_t size, size_t nmemb, void *userp){  struct upload_status *upload_ctx = (struct upload_status *)userp;  const char *data;  if((size == 0) || (nmemb == 0) || ((size*nmemb) < 1)) {    return 0;  }  data = payload_text[upload_ctx->lines_read];  if(data) {    size_t len = strlen(data);    memcpy(ptr, data, len);    upload_ctx->lines_read++;    return len;  }  return 0;}int main(void){  CURL *curl;  CURLcode res = CURLE_OK;  struct curl_slist *recipients = NULL;  struct upload_status upload_ctx;  upload_ctx.lines_read = 0;  curl = curl_easy_init();  if(curl) {    /* This is the URL for your mailserver */    curl_easy_setopt(curl, CURLOPT_URL, "smtp://mail.example.com");    /* Note that this option isn't strictly required, omitting it will result     * in libcurl sending the MAIL FROM command with empty sender data. All     * autoresponses should have an empty reverse-path, and should be directed     * to the address in the reverse-path which triggered them. Otherwise,     * they could cause an endless loop. See RFC 5321 Section 4.5.5 for more     * details.     */    curl_easy_setopt(curl, CURLOPT_MAIL_FROM, FROM);    /* Add two recipients, in this particular case they correspond to the     * To: and Cc: addressees in the header, but they could be any kind of     * recipient. */    recipients = curl_slist_append(recipients, TO);    recipients = curl_slist_append(recipients, CC);    curl_easy_setopt(curl, CURLOPT_MAIL_RCPT, recipients);    /* We're using a callback function to specify the payload (the headers and     * body of the message). You could just use the CURLOPT_READDATA option to     * specify a FILE pointer to read from. */    curl_easy_setopt(curl, CURLOPT_READFUNCTION, payload_source);    curl_easy_setopt(curl, CURLOPT_READDATA, &upload_ctx);    curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L);    /* Send the message */    res = curl_easy_perform(curl);    /* Check for errors */    if(res != CURLE_OK)      fprintf(stderr, "curl_easy_perform() failed: %s\n",              curl_easy_strerror(res));    /* Free the list of recipients */    curl_slist_free_all(recipients);    /* curl won't send the QUIT command until you call cleanup, so you should     * be able to re-use this connection for additional messages (setting     * CURLOPT_MAIL_FROM and CURLOPT_MAIL_RCPT as required, and calling     * curl_easy_perform() again. It may not be a good idea to keep the     * connection open for a very long time though (more than a few minutes     * may result in the server timing out the connection), and you do want to     * clean up in the end.     */    curl_easy_cleanup(curl);  }  return (int)res;}

段错误原因：payload_text 数组其中任一个指针指向的字符串长度大于16000（之前程序在组合邮件内容时，其中一个指针指向了整个内容）
解决方法：把过长的邮件内容拆成多个字符串

深层原因：可能和 curl 实现有关系（需要深入研究）