c - 在哪里以及如何正确释放 malloc 指针？

Question

我现在正在学习 C 编程类(class)，正在制作一个类似于 bash 的 shell。现在，我正在致力于实现管道。因此，我需要strndup管道命令在解析时不修改原始管道命令。最后，我尝试free malloc 'd 指针，但是我的程序无法正常工作。有人可以告诉我我做错了什么吗？下面是我的解析器的 while 循环的代码:

   while (pipeSeparatedCommand != NULL) {
        char *duplicateCmdForPiping = strndup(pipeSeparatedCommand, strlen(pipeSeparatedCommand)); // duplicates command
        pipeSeparatedCommand = strtok(NULL, "|"); // starts at the NULL Character that was tokenized
        char *token = strtok(duplicateCmdForPiping, " "); // finds the first space in the command, tokenizes the arguments by this space
        int index = 0;  // counts the number of commands and arguments

        while (token != NULL) {
            if ((input != NULL) || (output != NULL)) { // advances to the next argument if input or output is found (does not include them in args)
                token = strtok(NULL, " "); 
                continue;
            }

            commandArgsCount[index]++;
            commandArray[numberOfPipes][index] = token; // sets the argument index equal to the address of token (containing the token)
            token = strtok(NULL, " "); // token will search for the next delimiter from the last delimiter end spot
            index++;    
        }

        commandArray[numberOfPipes + 1][index] = NULL; // prevents the args array from collecting garbage in memory.

        if (pipeSeparatedCommand != NULL) // catches the zero case
            numberOfPipes++; // this begins at zero, increments if more pipes need to be added

        free(duplicateCmdForPiping);
        duplicateCmdForPiping = NULL;
    }

Answer 1

查看 strtok() 的手册页。它说该函数将返回“指向字符串中每个后续标记的开头的指针”。建议你改一下线路

    commandArray[numberOfPipes][index] = token;

至

    // make sure you `#include <string.h>`
    strcpy(commandArray[numberOfPipes][index], token);
    // OR
    commandArray[numberOfPipes][index] = strdup(token);

顺便说一句，请避免在 C/C++ 中使用驼峰式变量命名约定。它使您的代码极难阅读。