curl_easy_perform返回值详解

本文详细解读了CURL库中一系列错误代码,包括连接失败、协议不支持、主机解析等问题,帮助开发者快速定位和解决网络请求过程中的各种问题。

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CURLE_OK = 0,
CURLE_UNSUPPORTED_PROTOCOL, /* 1 /
CURLE_FAILED_INIT, / 2 /
CURLE_URL_MALFORMAT, / 3 /
CURLE_NOT_BUILT_IN, / 4 - [was obsoleted in August 2007 for
7.17.0, reused in April 2011 for 7.21.5] /
CURLE_COULDNT_RESOLVE_PROXY, / 5 /
CURLE_COULDNT_RESOLVE_HOST, / 6 /
CURLE_COULDNT_CONNECT, / 7 /
CURLE_WEIRD_SERVER_REPLY, / 8 /
CURLE_REMOTE_ACCESS_DENIED, / 9 a service was denied by the server
due to lack of access - when login fails
this is not returned. /
CURLE_FTP_ACCEPT_FAILED, / 10 - [was obsoleted in April 2006 for
7.15.4, reused in Dec 2011 for 7.24.0]/
CURLE_FTP_WEIRD_PASS_REPLY, / 11 /
CURLE_FTP_ACCEPT_TIMEOUT, / 12 - timeout occurred accepting server
[was obsoleted in August 2007 for 7.17.0,
reused in Dec 2011 for 7.24.0]/
CURLE_FTP_WEIRD_PASV_REPLY, / 13 /
CURLE_FTP_WEIRD_227_FORMAT, / 14 /
CURLE_FTP_CANT_GET_HOST, / 15 /
CURLE_HTTP2, / 16 - A problem in the http2 framing layer.
[was obsoleted in August 2007 for 7.17.0,
reused in July 2014 for 7.38.0] /
CURLE_FTP_COULDNT_SET_TYPE, / 17 /
CURLE_PARTIAL_FILE, / 18 /
CURLE_FTP_COULDNT_RETR_FILE, / 19 /
CURLE_OBSOLETE20, / 20 - NOT USED /
CURLE_QUOTE_ERROR, / 21 - quote command failure /
CURLE_HTTP_RETURNED_ERROR, / 22 /
CURLE_WRITE_ERROR, / 23 /
CURLE_OBSOLETE24, / 24 - NOT USED /
CURLE_UPLOAD_FAILED, / 25 - failed upload “command” /
CURLE_READ_ERROR, / 26 - couldn’t open/read from file /
CURLE_OUT_OF_MEMORY, / 27 /
/ Note: CURLE_OUT_OF_MEMORY may sometimes indicate a conversion error
instead of a memory allocation error if CURL_DOES_CONVERSIONS
is defined
/
CURLE_OPERATION_TIMEDOUT, / 28 - the timeout time was reached /
CURLE_OBSOLETE29, / 29 - NOT USED /
CURLE_FTP_PORT_FAILED, / 30 - FTP PORT operation failed /
CURLE_FTP_COULDNT_USE_REST, / 31 - the REST command failed /
CURLE_OBSOLETE32, / 32 - NOT USED /
CURLE_RANGE_ERROR, / 33 - RANGE “command” didn’t work /
CURLE_HTTP_POST_ERROR, / 34 /
CURLE_SSL_CONNECT_ERROR, / 35 - wrong when connecting with SSL /
CURLE_BAD_DOWNLOAD_RESUME, / 36 - couldn’t resume download /
CURLE_FILE_COULDNT_READ_FILE, / 37 /
CURLE_LDAP_CANNOT_BIND, / 38 /
CURLE_LDAP_SEARCH_FAILED, / 39 /
CURLE_OBSOLETE40, / 40 - NOT USED /
CURLE_FUNCTION_NOT_FOUND, / 41 - NOT USED starting with 7.53.0 /
CURLE_ABORTED_BY_CALLBACK, / 42 /
CURLE_BAD_FUNCTION_ARGUMENT, / 43 /
CURLE_OBSOLETE44, / 44 - NOT USED /
CURLE_INTERFACE_FAILED, / 45 - CURLOPT_INTERFACE failed /
CURLE_OBSOLETE46, / 46 - NOT USED /
CURLE_TOO_MANY_REDIRECTS, / 47 - catch endless re-direct loops /
CURLE_UNKNOWN_OPTION, / 48 - User specified an unknown option /
CURLE_TELNET_OPTION_SYNTAX, / 49 - Malformed telnet option /
CURLE_OBSOLETE50, / 50 - NOT USED /
CURLE_PEER_FAILED_VERIFICATION, / 51 - peer’s certificate or fingerprint
wasn’t verified fine /
CURLE_GOT_NOTHING, / 52 - when this is a specific error /
CURLE_SSL_ENGINE_NOTFOUND, / 53 - SSL crypto engine not found /
CURLE_SSL_ENGINE_SETFAILED, / 54 - can not set SSL crypto engine as
default /
CURLE_SEND_ERROR, / 55 - failed sending network data /
CURLE_RECV_ERROR, / 56 - failure in receiving network data /
CURLE_OBSOLETE57, / 57 - NOT IN USE /
CURLE_SSL_CERTPROBLEM, / 58 - problem with the local certificate /
CURLE_SSL_CIPHER, / 59 - couldn’t use specified cipher /
CURLE_SSL_CACERT, / 60 - problem with the CA cert (path?) /
CURLE_BAD_CONTENT_ENCODING, / 61 - Unrecognized/bad encoding /
CURLE_LDAP_INVALID_URL, / 62 - Invalid LDAP URL /
CURLE_FILESIZE_EXCEEDED, / 63 - Maximum file size exceeded /
CURLE_USE_SSL_FAILED, / 64 - Requested FTP SSL level failed /
CURLE_SEND_FAIL_REWIND, / 65 - Sending the data requires a rewind
that failed /
CURLE_SSL_ENGINE_INITFAILED, / 66 - failed to initialise ENGINE /
CURLE_LOGIN_DENIED, / 67 - user, password or similar was not
accepted and we failed to login /
CURLE_TFTP_NOTFOUND, / 68 - file not found on server /
CURLE_TFTP_PERM, / 69 - permission problem on server /
CURLE_REMOTE_DISK_FULL, / 70 - out of disk space on server /
CURLE_TFTP_ILLEGAL, / 71 - Illegal TFTP operation /
CURLE_TFTP_UNKNOWNID, / 72 - Unknown transfer ID /
CURLE_REMOTE_FILE_EXISTS, / 73 - File already exists /
CURLE_TFTP_NOSUCHUSER, / 74 - No such user /
CURLE_CONV_FAILED, / 75 - conversion failed /
CURLE_CONV_REQD, / 76 - caller must register conversion
callbacks using curl_easy_setopt options
CURLOPT_CONV_FROM_NETWORK_FUNCTION,
CURLOPT_CONV_TO_NETWORK_FUNCTION, and
CURLOPT_CONV_FROM_UTF8_FUNCTION /
CURLE_SSL_CACERT_BADFILE, / 77 - could not load CACERT file, missing
or wrong format /
CURLE_REMOTE_FILE_NOT_FOUND, / 78 - remote file not found /
CURLE_SSH, / 79 - error from the SSH layer, somewhat
generic so the error message will be of
interest when this has happened */

CURLE_SSL_SHUTDOWN_FAILED, /* 80 - Failed to shut down the SSL
connection /
CURLE_AGAIN, / 81 - socket is not ready for send/recv,
wait till it’s ready and try again (Added
in 7.18.2) /
CURLE_SSL_CRL_BADFILE, / 82 - could not load CRL file, missing or
wrong format (Added in 7.19.0) /
CURLE_SSL_ISSUER_ERROR, / 83 - Issuer check failed. (Added in
7.19.0) /
CURLE_FTP_PRET_FAILED, / 84 - a PRET command failed /
CURLE_RTSP_CSEQ_ERROR, / 85 - mismatch of RTSP CSeq numbers /
CURLE_RTSP_SESSION_ERROR, / 86 - mismatch of RTSP Session Ids /
CURLE_FTP_BAD_FILE_LIST, / 87 - unable to parse FTP file list /
CURLE_CHUNK_FAILED, / 88 - chunk callback reported error /
CURLE_NO_CONNECTION_AVAILABLE, / 89 - No connection available, the
session will be queued /
CURLE_SSL_PINNEDPUBKEYNOTMATCH, / 90 - specified pinned public key did not
match /
CURLE_SSL_INVALIDCERTSTATUS, / 91 - invalid certificate status /
CURLE_HTTP2_STREAM, / 92 - stream error in HTTP/2 framing layer
/
CURLE_RECURSIVE_API_CALL, / 93 - an api function was called from
inside a callback /
CURL_LAST / never use! */

<think>嗯,用户这次提出了一个非常具体的C语言网络编程问题:curl_easy_perform函数因内存不足导致失败,需要解决方案。这个问题在资源受限的嵌入式系统中尤其常见。用户引用了三个站内参考,但只有引用[2]与curl功能相关,其他两个(Go内存泄露和Gemma模型微调)明显是干扰项。这说明用户可能之前进行过宽泛的技术搜索,但当前问题非常聚焦。回顾历史对话,用户对技术细节有较强的理解能力,之前讨论过Python算法实现,现在转向C语言的网络编程问题,可能是从事系统开发或物联网相关工作。用户能准确指出curl_easy_perform这个具体函数,说明已经完成了基础排查。从技术角度看,这个问题需要从三个维度分析:1.cURL自身的内存管理机制,特别是CURLOPT_BUFFERSIZE等关键参数2.系统层面的资源监控策略,防止单一进程耗尽资源3.数据传输过程中的内存优化技巧用户没有提供具体错误代码,但根据经验,CURLE_OUT_OF_MEMORY(errorcode27)通常发生在:处理大文件时默认缓冲区不足,或操作系统线程分配失败。有趣的是,这个错误有时具有欺骗性——实际可能是FD数量耗尽或线程创建失败,而非物理内存不足。解决方案应该突出优先级:首先验证是否真正是内存问题(用valgrind),再实施内存控制策略。特别要注意cURL的多部分表单(multipart/form-data)使用,它会在内存中构建整个请求体,对上传大文件极其危险。考虑到用户是开发者,回复需要保持技术严谨性。代码示例选择CURLOPT_CHUNK_BGN_FUNCTION回调函数作为展示,因为这是处理大文件最有效的内存控制方案之一。同时提示关注连接复用(CURLMOPT_MAXCONNECTS),这个隐藏参数经常被忽视。最后需要设置安全边界:明确说明什么情况下应该放弃软件优化(如超过500MB的文件传输),转而使用硬件升级方案。用户可能面临老板要求“软件解决一切”的压力,作为专业建议应该给出明确的技术红线。</think> 遇到`curl_easy_perform()`因内存不足失败的问题时,可尝试以下系统级解决方案: --- ### 一、核心优化策略 1. **流式处理大文件** ```c // 避免完整加载文件到内存 curl_easy_setopt(curl, CURLOPT_READFUNCTION, read_callback); curl_easy_setopt(curl, CURLOPT_READDATA, fp); ``` - 实现`read_callback`函数逐步读取文件,而非一次性加载到内存[^2] 2. **限制响应缓存** ```c // 直接写入文件而非内存 curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data); curl_easy_setopt(curl, CURLOPT_WRITEDATA, fp); // 或设置内存上限 curl_easy_setopt(curl, CURLOPT_BUFFERSIZE, 16384); // 16KB缓冲区 ``` 3. **复用连接池** ```c // 全局启用连接复用 curl_easy_setopt(curl, CURLOPT_TCP_KEEPALIVE, 1L); curl_easy_setopt(curl, CURLOPT_FORBID_REUSE, 0L); // 使用curl_multi接口管理连接池[^2] ``` --- ### 二、内存泄漏检测 1. **启用cURL调试** ```c curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L); // 输出调试信息 curl_easy_setopt(curl, CURLOPT_STDERR, stderr); ``` 2. **使用Valgrind检测** ```bash valgrind --leak-check=full ./your_program ``` 3. **检查全局变量** - 避免在全局数组中缓存cURL数据(参考内存泄漏警告[^1]) --- ### 三、系统级配置 1. **调整内核参数** ```bash # 增加TCP缓冲区 sysctl -w net.core.rmem_max=16777216 sysctl -w net.core.wmem_max=16777216 ``` 2. **优化SSL配置** ```c curl_easy_setopt(curl, CURLOPT_SSLVERSION, CURL_SSLVERSION_TLSv1_2); curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0L); // 非生产环境可禁用证书验证 ``` --- ### 四、备选方案 当处理超大文件(>500MB)时: 1. **分段下载** ```c curl_easy_setopt(curl, CURLOPT_RANGE, "0-1999999"); // 下载前20MB ``` 2. **改用异步接口** - 使用`curl_multi_perform()`实现非阻塞传输 --- **关键参数说明**: | 参数 | 推荐值 | 作用 | |--------------------------|---------------|--------------------------| | `CURLOPT_BUFFERSIZE` | 16384 (16KB) | 减少单次读写内存占用 | | `CURLOPT_TCP_KEEPALIVE` | 1 (启用) | 连接复用降低资源开销 | | `CURLOPT_LOW_SPEED_TIME` | 60秒 | 自动终止无响应连接 | > 注:资源密集场景建议采用增量处理策略,每次仅操作数据片段[^2] --- ###
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