c - 为什么我需要这条线，据我所知它是多余的

Question

下面是我用于解析标记的一段代码。

底部附近有一行用 >>>> 指示，不再需要，但如果我将其注释掉，cmd_parse_value_lookup() 函数将失败。如果我把它留在里面，代码就会正常运行。谁能告诉我原因，并解释发生了什么？

void cmd_parse(void)
  {
    cmd_parse_value=0;  
    int cmd_parse_counter = 1;
    char *cmd_parse_pointer;
    cmd_parse_pointer = strtok(cmd_buffer_in, " ");
    if (cmd_parse_pointer!=NULL)
    {
      cmd_parse_value_lookup(cmd_parse_pointer);
    }
    while (cmd_parse_pointer != NULL)
    {
      cmd_parse_counter++;
      cmd_parse_pointer = strtok(NULL, " ");
      if (cmd_parse_pointer!=NULL)
      {
   >>>>cmd_buffer_sprintf_return = sprintf(cmd_buffer_sprintf,"%i: %s\r\n", cmd_parse_counter, cmd_parse_pointer);  //WHY DO I NEED THIS LINE
        cmd_parse_value_lookup(cmd_parse_pointer);
      }
    }
  }

void cmd_parse_value_lookup(char *cmd_command)
{
  if (strcmp(cmd_command,"show")==0)
  {
    cmd_parse_value |= 1;
  }
  else if (strcmp(cmd_command,"get")==0)
  {
    cmd_parse_value |= 1;
  } 
  else if (strcmp(cmd_command,"set")==0)
  {
    cmd_parse_value |= 2;
  }
  else if (strcmp(cmd_command,"system")==0)
  {
    cmd_parse_value |= 4;
  }
}

编辑:这是完整的代码:

/** C O M M A N D ************************************************************/

#include "generic.h"
#include <stdio.h>
#include <string.h>

void btm_out_character (char character);
void btm_out_string(char *string);
void cmd_parse(void);

char cmd_buffer_in[81]="\0                                                                         ";
int cmd_buffer_in_position=0;
unsigned long long cmd_parse_value=0;

char cmd_buffer_sprintf[81];
int cmd_buffer_sprintf_return;

void cmd_parse_value_lookup(char *cmd_command);
void cmd_buffer_in_add(int character);

void cmd_init(void)
{

}

void cmd_cls(void)
{
    if (dbg_mode==1){btm_out_string("\033[2J\033[1;33;40m\033[H\r\n");}
    if (dbg_mode==1){btm_out_string("================================================================================");}
    if (dbg_mode==1){btm_out_string("\033[24;0H================================================================================");}
    if (dbg_mode==1){btm_out_string("\033[1;36;40m\033[8;66H DEBUG MODE ");}
    if (dbg_mode==1){btm_out_string("\033[24;7H ***** ******** ********** Engineering Limited, All Rights Reserved ");}
    if (dbg_mode==1){btm_out_string("\033[10;0H");}
}   

void cmd_prompt(void)
{
    cmd_buffer_in_position = 0; // Clear buffer position
    cmd_buffer_in[0]=0;  // Clear buffer
    if (dbg_mode==1){btm_out_string("\r\n\033[1;37;40m***:> ");}    
}

void cmd_buffer_in_add(int character)
{
    switch (character)
    {
        case 8:
            if (cmd_buffer_in_position>0)
            {
                if (dbg_mode==1){btm_out_string("\b \b");}
                cmd_buffer_in[(int)cmd_buffer_in_position-1] = (char)character;
                cmd_buffer_in[(int)cmd_buffer_in_position] = 0;
                cmd_buffer_in_position--;
            }
                else
            {
                if (dbg_mode==1){btm_out_character(7);}     //BELL alert (too long a string)
                cmd_buffer_in[0] = 0;
                cmd_buffer_in_position = 0;
            }
            break;
        case 13:
            cmd_parse();
            cmd_buffer_sprintf_return = sprintf(cmd_buffer_sprintf,"\r\nparse value=%llu\r\n", cmd_parse_value);
            if (dbg_mode==1){btm_out_string(cmd_buffer_sprintf);}
            cmd_prompt();
            break;
        default:
            if (cmd_buffer_in_position<73)
            {
                if (dbg_mode==1){btm_out_character((char)character);}       //Echo character to host
                cmd_buffer_in[(int)cmd_buffer_in_position] = (char)character;
                cmd_buffer_in[(int)cmd_buffer_in_position+1] = 0;
                cmd_buffer_in_position++;
            }
            else
            {
                if (dbg_mode==1){btm_out_character(7);}     //BELL alert (too long a string)
            }
    }//switch
}//cmd_buffer_in_add

void cmd_parse(void)
{
    cmd_parse_value=0;

    /* this was code for testing */
    //cmd_buffer_sprintf_return = sprintf(cmd_buffer_sprintf,"\r\nClone %s",cmd_buffer_in);
    //cmd_buffer_sprintf_return = sprintf(cmd_buffer_sprintf,"Returnval='%i''%i''%i'",cmd_buffer_in[(int)0],cmd_buffer_in[(int)1],cmd_buffer_in[(int)2]);
    //if (dbg_mode==1){btm_out_string(cmd_buffer_sprintf);}

    int cmd_parse_counter = 1;
  char *cmd_parse_pointer;

  cmd_parse_pointer = strtok(cmd_buffer_in, " ");
  if (cmd_parse_pointer!=NULL)
    {
    cmd_parse_value_lookup(cmd_parse_pointer);
  }
  while (cmd_parse_pointer != NULL)
  {
      cmd_parse_counter++;
    cmd_parse_pointer = strtok(NULL, " ");
    if (cmd_parse_pointer!=NULL)
    {
        cmd_buffer_sprintf_return = sprintf(cmd_buffer_sprintf,"%i: %s\r\n", cmd_parse_counter, cmd_parse_pointer);  //WHY DO I NEED THIS LINE
            //if (dbg_mode==1){btm_out_string(cmd_buffer_sprintf);}
            cmd_parse_value_lookup(cmd_parse_pointer);
    }
  }
}

void cmd_parse_value_lookup(char *cmd_command)
{
    if (strcmp(cmd_command,"show")==0)
    {
        cmd_parse_value |= 1;
    }
    else if (strcmp(cmd_command,"get")==0)
    {
        cmd_parse_value |= 1;
    } 
    else if (strcmp(cmd_command,"set")==0)
    {
        cmd_parse_value |= 2;
    }
    else if (strcmp(cmd_command,"system")==0)
    {
        cmd_parse_value |= 4;
    }
    else if (strcmp(cmd_command,"sys")==0)
    {
        cmd_parse_value |= 4;
    }
    else if (strcmp(cmd_command,"adc")==0)
    {
        cmd_parse_value |= 8;
    }
    else if (strcmp(cmd_command,"a2d")==0)
    {
        cmd_parse_value |= 8;
    }
    else if (strcmp(cmd_command,"channel1")==0)//
    {
        cmd_parse_value |= 16;
    }
    else if (strcmp(cmd_command,"ch1")==0)
    {
        cmd_parse_value |= 16;
    }
}

Answer 1

由于您不在其他任何地方使用cmd_buffer_sprintf，因此该行代码似乎毫无用处。可能的情况是 cmd_buffer_sprintf 是您在其他地方使用的全局变量，但在您提供的代码段中，该行不会改变任何内容。