cout无法输出常量字符串但可输出变量的问题排查

Let's break down what's going wrong here and fix it step by step.

The Root Cause #

Your code uses getline(myFile, str, '-') to split the entire file by the '-' character, instead of first reading each task record line by line. This causes critical issues because:

• When a task ends with a newline followed by the next record's date, that newline and date get included in the next split string.
• This mixes up your date/task pairs and introduces unexpected line breaks, leading to missing labels in subsequent output.

For example, take the first two lines of your calend.txt:

15/05-checkpoint IART
18/05-checkpoint COMP

With '-' as the delimiter:

1. First getline reads "15/05" (good)
2. Second getline reads "checkpoint IART\n18/05" (includes the newline and next date)
3. When you output this, the \n forces "18/05" to print on its own line
4. Next split gives you "checkpoint COMP" and "\n22/05", so you end up printing date: checkpoint COMP (completely reversed!)

The Solution: Read Lines First, Split Second #

The correct approach is to read each full line of the file first, then split that line into date and task using '-'. This keeps each record isolated and avoids mixing content between lines.

Here's the corrected code:

#include <iostream>
#include <fstream>
#include <string>
using namespace std;

int main() {
    ifstream myFile("calend.txt");
    string line;
    
    // Read one full task record at a time
    while (getline(myFile, line)) {
        // Locate the '-' that separates date and task
        size_t dashPosition = line.find('-');
        
        if (dashPosition != string::npos) {
            // Split the line into date (before '-') and task (after '-')
            string date = line.substr(0, dashPosition);
            string task = line.substr(dashPosition + 1);
            
            // Print with consistent labels
            cout << "date: " << date << endl;
            cout << "task: " << task << endl;
        } else {
            // Handle lines that don't follow the date-task format
            cout << "Warning: Invalid line format -> " << line << endl;
        }
    }
    
    myFile.close();
    system("pause");
    return 0;
}

What This Fix Does #

• Isolates records: Reading full lines ensures each date-task pair stays together, no cross-line contamination.
• Clean splitting: Using string::find and substr gives precise control over where to split each line.
• Error handling: Adds a warning for lines without a '-' to avoid unexpected crashes or garbage output.

Expected Output #

Running this corrected code with your calend.txt will produce the consistent, labeled output you want:

date: 15/05
task: checkpoint IART
date: 18/05
task: checkpoint COMP
date: 22/05
task: SDIS
date: 25/05
task: apresentacao PPIN
date: 27/05
task: IART
date: 28/05
task: apresentacao LPOO
date: 28/05
task: teste PPIN
date: 01/06
task: LBAW
date: 05/06
task: COMP
date: 08*14/06
task: PPIN

内容的提问来源于stack exchange，提问作者NoHoly