c++ - break 语句的段错误？

Question

我只是通过一个 switch 语句:

case RoutingMessage::FWDMESSAGE:
        {
                //Message Format:
                //@FromNode~12~DestNode.from x to y hops .<the message>
                int destID;
                string changableStr, finalMessage;
                string buf(iter->second);
                string delim = ".";
                destID = atoi(buf.substr(0, buf.find(delim)).c_str());
                buf.erase(0, buf.find(delim) + delim.length());

                changableStr = buf.substr(0, buf.find(delim));

                stringstream sstm;
                sstm << changableStr << " " << myID-3700;
                changableStr = sstm.str();
                buf.erase(0, buf.find(delim) + delim.length());

                string theMsg = buf.substr(0, buf.find(delim));

                stringstream sstm2;
                sstm2 << changableStr << "." << theMsg;
                finalMessage = sstm2.str();

                cout << "FINAL MESSAGE: " << finalMessage << endl;

                if(myID == destID)
                    cout << "\t\t\tMINE\n";
                    //PrintMessage(iter->)
                else
                {
                    neighbor.sin_port = forwardingTable.at(destID).begin()->first;
                    char *cstr = new char[finalMessage.length() + 1];
                    strcpy(cstr, finalMessage.c_str());
                    char* buf;
                    sprintf(buf, "@%d~%d~%d.%s", myID, RoutingMessage::FWDMESSAGE, destID, cstr);
                    SendMessage(neighbor, buf);
                }
                cout << "test\n";
                break;
                cout << "test2\n";
            }

但是，当我点击 break; 时，gdb 吐出:

Program received signal SIGSEGV, Segmentation fault.
__GI___libc_free (mem=0x32317e3130373340) at malloc.c:2892
2892    malloc.c: No such file or directory.
(gdb) backtrace
#0  __GI___libc_free (mem=0x32317e3130373340) at malloc.c:2892
#1  0x00007ffff7b43cab in std::ios_base::~ios_base() () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#2  0x00007ffff7b6ea13 in std::basic_stringstream<char, std::char_traits<char>, std::allocator<char> >::~basic_stringstream() () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6

我从没见过这个...有人能帮忙吗？

Answer 1

看起来你正在 sprintfing 到这里未分配的缓冲区:

char* buf;
sprintf(buf, "@%d~%d~%d.%s", myID, RoutingMessage::FWDMESSAGE, destID, cstr);