这是错误消息图片的链接:
http://www.flickr.com/photos/76298377@N02/6798897020/in/photostream
这是实际的编程问题。这是 3 号
这是源代码
#include <iostream>
#include <string>
#include<stdio.h>
using namespace std;
#define numItems 8
#define numSalesP 10
// the product prices
float prices [numItems] = {345.0, 853.0, 471.0, 933.0, 721.0, 663.0, 507.0, 259.00};
// the product numbers
int prodNum [numItems] = {7, 8, 9, 10, 11, 12, 13, 14};
// the salespersons IDs
int salesP [numSalesP] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
// the output file pointers
FILE * filePtrs[numSalesP];
// sales totals for every salespersons
float totals [numSalesP];
//get the product index from the prodNum array
int getProdIndex (int product) {
int i;
for (i=0; i< numItems; i++) {
if (prodNum[i] == product) {
return i;
}
}
return -1;
}
// get a product price from the product index
float getProdPrice (int prodIndex) {
return prices[prodIndex];
}
// open a salesperson output file
void openSalesPFiles () {
int i;
char fileName[16];;
for (i=0; i<numSalesP; i++) {
sprintf(fileName, "salespers%d.dat", i+1);
//DEBUG cout << fileName << endl;
filePtrs[i] = fopen(fileName, "r");
}
}
// close Salespersons files
void closeSalesPFiles () {
int i;
for (i=0; i<numSalesP; i++) {
fclose(filePtrs[i]);
}
}
// get sales person index from its ID
int getSalesPIndex (int salesPerson) {
int i;
for (i=0; i< numSalesP; i++) {
if (salesP[i] == salesPerson) {
return i;
}
}
return -1;
}
int main () {
int i; // generic counter
FILE * salesFile; // the input file with all sales
int salesPId; // salesperson ID
int salesPIndex; // salesperson index in array
int prodId; // product ID
int pIndex; // product index in array
int qty; // quantity
float total; // total for one sale
// open all salespersons output files
openSalesPFiles();
// open the input file
salesFile = fopen("sales.dat", "r");
// read all record in the input file
while (!feof(salesFile)) {
fscanf(salesFile, "%d %d %d", &salesPId, &prodId, &qty);
//DEBUG cout << salesPId << " --- " << prodId << " --- " << qty << endl;
// validate sales person
salesPIndex = getSalesPIndex (salesPId);
if (salesPIndex < 0) {
cout << "Invalid Sales person ID " << salesPId << endl;
continue;
}
//DEBUG cout << "Salesperson index : " << salesPIndex << endl;
// validate product id
pIndex = getProdIndex (prodId);
if (pIndex < 0) {
cout << "invalid product id : " << prodId << endl;
fprintf(filePtrs[salesPIndex], "Invalid Product ID %d\n", prodId);
continue;
}
else {
// compute the sale total
total = qty * prices[pIndex];
//DEBUG cout << "total : " << total << endl;;
// add it to the totals for this salesperson
totals[salesPIndex] += (qty * prices[pIndex]);
// write the sale to the salesperson file
fprintf(filePtrs[salesPIndex], "%d %d %2.2f\n", prodId, qty, total);
}
}
// print totals in salespersons files
for (i=0; i< numSalesP; i++) {
fprintf(filePtrs[i], "Total Sales : %8.2f\n", totals[i]);
}
// close all files
closeSalesPFiles();
fclose(salesFile);
}
代码有什么问题会让我出现这样的错误?谢谢:S
最佳答案
断言来自名为feoferr.c的文件。这表明它与 feof 函数有关。该断言表示它期望 stream != NULL
。断言失败,因此 stream
显然是一个空指针。由于 feof
采用文件流参数,因此可以安全地猜测断言消息提到的流就是文件流参数。您可以这样调用 feof
:
// open the input file
salesFile = fopen("sales.dat", "r");
// read all record in the input file
while (!feof(salesFile)) {
所以也许 salesFile
是一个空指针。如您所知,当 fopen
无法打开文件时可能会发生这种情况。也许该文件不存在,或者您没有读取它的权限。
下次遇到错误时,请使用您面前的工具。你有一个调试器,当程序像这样失败时,它应该中断你的程序。它可以将您带到失败的行或最接近它的行。这应该会提示您,在您调用 fopen
后不久,问题就出现在某个地方。在那里开始调查。
稍后在代码中设置断点,并查看是否在程序失败之前到达它们。如果您没有做到这一点,那么当您发布问题时不要包含这些功能。不要用大量不相关的代码来筛选潜在的帮助者,以解决真正的问题。
当您遇到问题时,请确保您的函数返回您期望的值。如果您不知道他们会返回什么,请阅读文档并做一些实验。确保您理解您编写的所有代码。
关于c++ - 调试 C 程序的断言错误,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/9526240/