c - 来自 C 中输入文件的 fgets 的段错误

Question

此函数使用fgets 从文件输入数据并将其存储在结构中。我遇到了段错误，我不知道为什么。该程序不会运行，所以我无法调试。这是函数的代码:

void getInventory(NodeT **ppRoot, char *pszInventoryFileName)
{
    char szInputBuffer[100];       // input buffer for reading data
    int iScanfCnt;                 // returned by sscanf
    FILE *pfileInventory;          // Stream Input for Inventory data.
    Stock *pNew = NULL;

    /* open the Inventory stream data file */
    if (pszInventoryFileName == NULL)
            exitError(ERR_MISSING_SWITCH, "-i");

    pfileInventory = fopen(pszInventoryFileName, "r");
    if (pfileInventory == NULL)
            exitError(ERR_INVENTORY_FILENAME, pszInventoryFileName);

    /* get inventory data until EOF
    ** fgets returns null when EOF is reached.
    */
    while (fgets(szInputBuffer, 100, pfileInventory) != NULL)
    {
            iScanfCnt = sscanf(szInputBuffer, "%6s %ld %lf %30[^\n]\n"
                    , pNew->szStockNumber
                    , &pNew->lStockQty
                    , &pNew->dUnitPrice
                    , pNew->szStockName);

            if (iScanfCnt < 4)
                    exitError(ERR_INVALID_INVENTORY_DATA, "\n");

            if (pNew == NULL)
                    exitError("Memory allocation error", "");

            printT(insertT(*ppRoot, *pNew));
    }
}

printT 和insertT 函数是递归的，但程序在执行到那一步之前就失败了。这是来自输入文件的数据:

PPF001 100 9.95 Popeil Pocket Fisherman
SBB001 300 14.95 Snuggie Brown
SBG002 400 14.95 Snuggie Green
BOM001 20 29.95 Bass-O-Matic
MCW001 70 12.45 Miracle Car Wax
TTP001 75 9.95 Topsy Turvy Planter
NHC001 300 9.95 Electric Nose Hair Clipper
SSX001 150 29.95 Secret Seal

为什么这段代码给我一个段错误？

Answer 1

问题是，虽然您正在检查 pNew 分配给 NULL，但实际上您从未向它分配内存。

添加对 malloc 的调用，分配给 pNew 并在 sscanf 调用之前进行内存检查以修复此问题:

while (fgets(szInputBuffer, 100, pfileInventory) != NULL)
{
        pNew = malloc(sizeof(Stock));
        if (pNew == NULL)
                exitError("Memory allocation error", "");

        iScanfCnt = sscanf(szInputBuffer, "%6s %ld %lf %30[^\n]\n"
                , pNew->szStockNumber
                , &pNew->lStockQty
                , &pNew->dUnitPrice
                , pNew->szStockName);

        if (iScanfCnt < 4)
                exitError(ERR_INVALID_INVENTORY_DATA, "\n");

        printT(insertT(*ppRoot, *pNew));
}