When I use gdb debugging, I often encounter problems with gdb failing in some places, what is going on?

I've only been involved with gdp for a short time and my knowledge of some of the issues is rather superficial, so I'm afraid I can't describe my questions in a very logical and professional way now. Common sense dictates that when the n command is entered under gdp, it will execute to the next statement. However, I occasionally encounter a problem where, after typing n and entering, gdp seems to be disabled and the gdp command line seems to turn into a terminal where you can type in as many characters as you like, but does not do anything with the input, just like the following:

`(gdb) 
(gdb) n
[New Thread 0x7ffff724e640 (LWP 7692)]
65              if ((st.st_mode & S_IFMT) == S_IFDIR)
(gdb) n
67              if ((st.st_mode & S_IXUSR) || (st.st_mode & S_IXGRP) || (st.st_mode & S_IXOTH))
(gdb) n
69              if (!cgi)
(gdb) n
70                    serve_file(client, path);
(gdb) n
n
nsdadsadsd
asdas
dasdasd
sdasd

The contents of serve_file.cpp and get_line.cpp are as follows:

#include "tinyhttp.h"
void serve_file(int client, const char *filename)
{
      using std::fstream;
      fstream fr(filename, fstream::in);
      std::string buf;
      int numchars = 1;
      while ((numchars > 0) && buf != "\n")
      {
            numchars = get_line(client, &buf);
            std::string().swap(buf);
      }
      if (!fr)
            not_found(client);
      else
      {
            headers(client, filename);
            cat(client, fr);
      }
      fr.close();
}

get_line.cpp:

#include "tinyhttp.h"
int get_line(int client, std::string *buf)
{
      char c = '\0';
      int n;
      while (c != '\n')
      {
            n = recv(client, &c, 1, 0);
            if (n > 0)
            {
                  if (c == '\r')
                  {
                        n = recv(client, &c, 1, MSG_PEEK);
                        if (n > 0 && c == '\n')
                              recv(client, &c, 1, 0);
                        else
                              c = '\n';
                  }
                  *buf += c;
            }
            else
                  c = '\n';
      }
      return (*buf).size();
}

What is this question, please?