c - 在 Ubuntu 中出现段错误(核心转储)错误

Question

我正在尝试构建一个程序，它将作为汇编程序运行，它将获取文件名作为命令行参数并将它们转换为机器代码。

程序编译得很好，使用一个文件名运行正常，但是当我尝试使用多个文件名运行时，在第一次迭代后出现错误。

我认为 Clear() 函数可能有一些东西(它清除了上一次迭代中分配的所有数据)，但不确定为什么。请注意，这是部分的，但正如我所说，除非使用多个文件，否则程序将运行。

struct symbolStruct { // a structure which is used to absorb info about a tag, its place in memory and related flags
    char *name;
    int place;
    unsigned int isEntry : 1;
    unsigned int isData : 1;
    unsigned int isExternal : 1;
    struct symbolStruct *next;
};

typedef struct { // a structure which is used to absorb info about the operand structure of an instruction line
    unsigned int numOfOperands : 2;
    unsigned int addrMethSou : 2;
    unsigned int addrMethDest : 2;
    unsigned int operation : 4;
    unsigned int extraWords : 2;
    char *firstOperand;
    char *secondOperand;
} OperandType;

typedef struct {
    unsigned int row : WORD_SIZE;
} int15;

struct MachineCode { // a structure which is used to absorb machine code lines, and their location in the assembly file
    unsigned int row : WORD_SIZE;
    unsigned int line;
    OperandType *structure;
    struct MachineCode *next;
};

struct DataCode { // a structure which is used to absorb data and string elements (signed numbers and ascii characters)
    unsigned int row : WORD_SIZE;
    struct DataCode *next;
};

struct Operation { /* the main operation structure, contains pointers to all used lists, the ic and dc counters, the
    current line number which is dealt with and the error flag. */
    unsigned int ic;
    unsigned int dc;
    struct symbolStruct *externHead; // a pointer to a linked list of extern tags used in the assembly file, and their locations
    struct symbolStruct *symbolHead; // a pointer to a linked list of all tags
    struct DataCode *dataHead; // a pointer to a linked list of all data/string elements
    struct MachineCode *machineHead; // a pointer to a linked list of all machine code rows
    int linenumber;
    unsigned int errorflag : 1; // raised in case of an error which triggered a warning
};

#include "header.h"

void FirstRun(struct Operation*, char *);
void DataUpdate(struct symbolStruct*,int);
void SecondRun(struct Operation *, char *);
void Clear(struct Operation *);

int main(int argc, char *argv[]) {
    int i;
    struct Operation programCore = {0,0,NULL,NULL,NULL,NULL,0,0};
    for(i=1;i<argc;i++) {
        char *fn = argv[i];
        FirstRun(&programCore,fn);
        DataUpdate(programCore.symbolHead,programCore.ic+INSTRUCTION_OFFSET);
        SecondRun(&programCore,fn);
        Clear(&programCore);
        programCore.symbolHead = programCore.externHead = programCore.dataHead = programCore.machineHead = NULL;
    }
    if(argc < 2) {
        fprintf(stderr,"No files selected.\n");
    }
    return 0;
}

/*Used to empty the linked lists and allocated memory after the program has finished one iteration. */
void Clear(struct Operation *programCore) { 
    /*f(pointer name) is there to hold a pointer to the allocated memory which is about to be flushed. */
    struct MachineCode *machineHead = programCore->machineHead, *fMachineHead; 
    struct DataCode *dataHead = programCore->dataHead, *fDataHead; 
        struct symbolStruct *externHead = programCore->externHead, *fExternHead;
    struct symbolStruct *symbolHead = programCore->symbolHead, *fSymbolHead;
    while(machineHead != NULL) {
            fMachineHead = machineHead;
        machineHead = machineHead->next;
        if(fMachineHead->structure != NULL) {
            if(fMachineHead->structure->numOfOperands == 2)
                free(fMachineHead->structure->secondOperand);
            if(fMachineHead->structure->numOfOperands > 0)
                free(fMachineHead->structure->firstOperand);
            free(fMachineHead->structure);
        }
        free(fMachineHead);
    }
    while(dataHead != NULL) {
        fDataHead = dataHead;
        dataHead = dataHead->next;
        free(fDataHead);
    }
    while(externHead != NULL) {
        fExternHead = externHead;
        externHead = externHead->next;
        free(fExternHead->name);
        free(fExternHead);
    }
    while(symbolHead != NULL) {
        fSymbolHead = symbolHead;
        symbolHead = symbolHead->next;
        free(fSymbolHead->name);
        free(fSymbolHead);
    }
    programCore->ic = programCore->dc = programCore->linenumber = programCore->errorflag = 0;
}

Answer 1

您不会释放和取消上下文结构 (programCore) 中的链表。我怀疑您当时正在使用指向已释放内存块的指针。

这一行只复制指针:

struct MachineCode *machineHead = programCore->machineHead;

while() 循环不清除 programCore->machineHead

要修复它，直接在头上运行:

while(programCore->machineHead != NULL)
{
    ...
}