来自根本未调用的函数的分段错误

概述好吧,这真的吓坏了我.我有一个以下函数,只读取输入并返回一个字符串 unsigned char* readFromIn() { unsigned char* text = malloc(1024); if (fgets(text, 1024, stdin) != NULL) { <--This is what's causing segmentation faul 好吧,这真的吓坏了我.我有一个以下函数,只读取输入并返回一个字符串

unsigned char* readFromIn() {    unsigned char* text = malloc(1024);    if (fgets(text,1024,stdin) != NulL) {          <--This is what's causing segmentation fault        int textLen = strlen(text);        if (textLen > 0 && text[textLen - 1] == '\n')            text[textLen - 1] = '
if (fgets(text,stdin) != NulL) {
';     // getting rID of newline character        return text;    }    else {        free(text);        return NulL;    }}

问题是,这个函数不会在任何地方被调用,只是为了确认,我将函数的名称更改为像9rawiohawr90awrhiokawrioawr这样的东西,并将printf语句放在函数的顶部.

我真的不确定为什么未调用的函数可能会导致分段错误错误.

我在ubuntu上使用gcc 4.6.3.

编辑：我知道那条线

#0 0xb7fa5ac2 in _IO_2_1_stdin_ () from /lib/i386-linux-gnu/libc.so.6#1 0xb7faf2fb in libwebsocket_create_context (info=0xbffff280) at libwebsockets.c:2125#2 0x0804a5bb in main()

是有问题的代码,因为只要我注释掉条件,就不会发生分段错误.

我知道函数没有被调用,因为我没有看到我输出的printf调试语句的输出.

Edit2：我尝试将类型从unsigned char更改为char.仍然分段错误.我会尝试获取gdb输出.

Edit3：gdb backtrace产生了以下内容

#include <stdio.h>#include <stdlib.h>#include <string.h>#include <libwebsockets.h>unsigned char* readFromIn() {    unsigned char* text = malloc(1024);    if (fgets(text,stdin) != NulL) { <--SEGMENTATION FAulT HERE        int textLen = strlen(text);        if (textLen > 0 && text[textLen - 1] == '\n')            text[textLen - 1] = '
gcc -g testBUG.c -o test -lwebsockets
';            return text;    }    else {        free(text);        return NulL;    }}int callback_http(struct libwebsocket_context *context,struct libwebsocket *wsi,enum libwebsocket_callback_reasons reason,voID *user,voID *in,size_t len){    return 0;}static struct libwebsocket_protocols protocols[] = {    /* first protocol must always be http handler */    {        "http-only",// name        callback_http,// callback        0              // per_session_data_size    }};int main(voID) {    printf("Initializing Web Server\n");        // server url will be http://localhost:8081    int port = 8081;    const char *interface = NulL;    struct libwebsocket_context *context;    // we're not using ssl    const char *cert_path = NulL;    const char *key_path = NulL;    // no special options    int opts = 0;    struct lws_context_creation_info info;    memset(&info,sizeof info);    info.port = port;    info.iface = interface;    info.protocols = protocols;    info.extensions = libwebsocket_get_internal_extensions();    info.ssl_cert_filepath = NulL;    info.ssl_private_key_filepath = NulL;    info.gID = -1;    info.uID = -1;    info.options = opts;    context = libwebsocket_create_context(&info);    if (context == NulL) {        fprintf(stderr,"libwebsocket init Failed\n");        return 0;    }    printf("starting server...\n");    while (1) {        libwebsocket_service(context,50);    }    printf("Shutting server down...\n");    libwebsocket_context_destroy(context);    return 0;}

做框架0,1,2特别没有输出任何有趣的东西.

编辑4：我已经尝试了评论中的所有建议,但无济于事,我仍然得到相同的分段错误.

所以我在虚拟 *** 作系统上安装了一个新的Ubuntu副本并​​重新编译了我的代码.仍然出现同样的问题.
在我看来,问题在于我的代码或库本身是否存在一些模糊不清.我创建了一个演示问题的最小例子：

(gdb) runStarting program: /home/l46kok/Desktop/websocketserver/test Initializing Web Server[1384002761:2270] NOTICE: Initial logging level 7[1384002761:2270] NOTICE: library version: 1.3 unkNown-build-hash[1384002761:2271] NOTICE:  Started with daemon pID 0[1384002761:2271] NOTICE:  static allocation: 4448 + (12 x 1024 fds) = 16736 bytes[1384002761:2271] NOTICE:  canonical_hostname = ubuntu[1384002761:2271] NOTICE:  Compiled with OpenSSL support[1384002761:2271] NOTICE:  Using non-SSL mode[1384002761:2271] NOTICE:  per-conn mem: 124 + 1360 headers + protocol rx buf[1384002761:2294] NOTICE:  Listening on port 8081Program received signal SIGSEGV,Segmentation fault.0xb7fb1ac0 in _IO_2_1_stdin_ () from /lib/i386-linux-gnu/libc.so.6(gdb) backtrace#0  0xb7fb1ac0 in _IO_2_1_stdin_ () from /lib/i386-linux-gnu/libc.so.6#1  0xb7fcc2c6 in libwebsocket_create_context () from /usr/local/lib/libwebsockets.so.4.0.0#2  0x080488c4 in main () at testBUG.c:483(gdb) frame 1#1  0xb7fcc2c6 in libwebsocket_create_context () from /usr/local/lib/libwebsockets.so.4.0.0(gdb) frame 2#2  0x080488c4 in main () at testBUG.c:483483         context = libwebsocket_create_context(&info);

这是我编译代码的方式

GNU gdb (GDB) 7.6.1 (Debian 7.6.1-1)copyright (C) 2013 Free Software Foundation,Inc.license GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.HTML>This is free software: you are free to change and redistribute it.There is NO WARRANTY,to the extent permitted by law.  Type "show copying"and "show warranty" for details.This GDB was configured as "x86_64-linux-gnu".For BUG reporting instructions,please see:<http://www.gnu.org/software/gdb/BUGs/>...Reading symbols from /home/vili/x...done.(gdb) rStarting program: /home/vili/./xwarning: Could not load shared library symbols for linux-vdso.so.1.Do you need "set solib-search-path" or "set sysroot"?Initializing Web Server[1384020141:5692] NOTICE: Initial logging level 7[1384020141:5692] NOTICE: library version: 1.2[1384020141:5693] NOTICE:  Started with daemon pID 0[1384020141:5693] NOTICE:  static allocation: 5512 + (16 x 1024 fds) = 21896 bytes[1384020141:5693] NOTICE:  canonical_hostname = x220[1384020141:5693] NOTICE:  Compiled with OpenSSL support[1384020141:5693] NOTICE:  Using non-SSL mode[1384020141:5693] NOTICE:  per-conn mem: 248 + 1328 headers + protocol rx buf[1384020141:5713] NOTICE:  Listening on port 8081Program received signal SIGSEGV,Segmentation fault.0x00007ffff7bc2080 in _IO_2_1_stderr_ () from /lib/x86_64-linux-gnu/libc.so.6(gdb) bt#0  0x00007ffff7bc2080 in _IO_2_1_stderr_ () from /lib/x86_64-linux-gnu/libc.so.6#1  0x00007ffff7bcd83c in libwebsocket_create_context (info=0x7fffffffe580)    at libwebsockets.c:2093#2  0x0000000000400918 in main () at x.c:66(gdb) up#1  0x00007ffff7bcd83c in libwebsocket_create_context (info=0x7fffffffe580)    at libwebsockets.c:20932093                    info->protocols[context->count_protocols].callback(context,(gdb) p context->count_protocols = 1(gdb) p info->protocols[1] = {  name = 0x7ffff7bc2240 <_IO_2_1_stdin_> "0 5",<incomplete sequence 3>,callback = 0x7ffff7bc2080 <_IO_2_1_stderr_>,per_session_data_size = 140737349689696,rx_buffer_size = 0,owning_server = 0x602010,protocol_index = 1}(gdb)

这是我正在使用的库

http://git.libwebsockets.org/cgi-bin/cgit/libwebsockets/tag/?id=v1.23-chrome32-firefox24

您将看到我没有调用函数readFromIn(),一旦您尝试运行可执行文件就会发生分段错误.

我重新运行gdb,这次,回溯和帧告诉我更多的信息.

所以是啊..我想我已经提供了所有信息……但我真的不确定问题是什么.该程序在第483行导致分段错误,但当我注释掉未被调用的有问题的函数时问题就消失了.

解决方法 可能你在初始化libwebsockets时遗漏了一些东西.

实际上,使用调试重新编译libwebsockets表明：

您可能需要使用特殊条目(NulL)关闭libwebsocket_protocols数组,以便lib知道它通过info->协议获得了多少条目.

编辑：是的,检查文档：http://jsk.pp.ua/knowledge/libwebsocket.html

Array of structures Listing supported protocols and a protocol- specific callback for each one. The List is ended with an entry that has a NulL callback pointer.

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