C:指向结构体内部函数的指针会导致段错误

Question

我必须创建链接列表。在这些列表中，我将定义指向函数的指针。我的错误是每当我调用该函数时，我都会收到段错误错误。任何人都可以帮忙吗，下面是我的代码:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>


typedef struct CommandStructure{
    char CommandName[10];
    char ShortKey;
    void (* CommandAction)(void);
} CommandFrame;

typedef struct LinkedCommandsStructure{
    CommandFrame * Entity;
    struct LinkedCommandsStructure * NextCommand;
} Firmware_Command; 


void PrintSEQHelp(){
    printf("HelloPrint \n");
}


CommandFrame * SEQ_Help(){
    CommandFrame * Entity = malloc(sizeof(Entity));

    strcpy(Entity->CommandName, "help");

    Entity->ShortKey = 'h';

    Entity->CommandAction = PrintSEQHelp; 

    return Entity;
}



Firmware_Command *  SEQ_CommandsInit(){

    Firmware_Command * HeadOfCommands    = malloc(sizeof(HeadOfCommands));
    Firmware_Command * HelpCommand       = malloc(sizeof(HelpCommand));

    HelpCommand->Entity = SEQ_Help();

    HelpCommand->NextCommand = NULL;

    HeadOfCommands = HelpCommand;

    return HeadOfCommands;
}


void callcommand(Firmware_Command * ActiveCommands){
    ActiveCommands = malloc(sizeof * ActiveCommands);
    printf("inside callcommand \n");

    (ActiveCommands->Entity->CommandAction)();      

}


int ModulesInit() {

    int ParseRet;

    Firmware_Command * ActiveCommands = malloc(sizeof(ActiveCommands));

    ActiveCommands = SEQ_CommandsInit();
    callcommand(ActiveCommands);

    return 1;
} 



void main(void){
    int cmdInitRet;

    cmdInitRet = ModulesInit();
}

Answer 1

您可以在有变量的代码中多次执行此操作，并为其分配内存，然后用其他值覆盖它。或者分配先前的值。至关重要的是，在 callcommand 函数中，您传入一个变量，然后用新的未初始化内存块覆盖它的值，然后尝试使用它。您不需要分配内存 - 传入的变量应该已经是有效的指针。

void callcommand(Firmware_Command * ActiveCommands){
    // ActiveCommands = malloc(sizeof * ActiveCommands); Not needed at all
    printf("inside callcommand \n");

    (ActiveCommands->Entity->CommandAction)();      

}