Скачать или смотреть How to Fix free(): invalid pointer Error in Your C+ + Program

Learn how to troubleshoot and resolve the `free(): invalid pointer` error that commonly occurs in C+ + programming. This guide helps you identify the problems in your code and provides effective solutions.
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This video is based on the question https://stackoverflow.com/q/67781000/ asked by the user 'Goemon0992' ( https://stackoverflow.com/u/15109450/ ) and on the answer https://stackoverflow.com/a/67781034/ provided by the user 'Sam Varshavchik' ( https://stackoverflow.com/u/3943312/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Fix free(): invalid pointer Error in Your C+ + Program

If you’re delving into C+ + programming, you may encounter various runtime errors that can halt your code execution. One particularly baffling error is the free(): invalid pointer message. In this guide, we will explore the cause of this error in a sample C+ + program and provide you with clear, actionable insights to resolve it.

Understanding the Problem

You're writing a simple C+ + program and encounter the error message: Error in `./a.out': free(): invalid pointer. This error usually indicates that your program is trying to release memory that hasn't been properly allocated, which can lead to undefined behavior and crashes. In this specific situation, several issues in the code contributed to this error, particularly around array indexing and function return types.

Let's dive into the C+ + code you've shared to identify the key bugs.

The Code in Question

Here's a snippet of the provided code:

[[See Video to Reveal this Text or Code Snippet]]

Analyzing the Bugs

1. Out-of-Bounds Access

In the extract_multis() function, we see this loop:

[[See Video to Reveal this Text or Code Snippet]]

When i is 0, input_c[i-1] will attempt to access input_c[-1], which is out of bounds and leads to undefined behavior. To fix this, you must adjust your loop to start from 1 instead of 0:

[[See Video to Reveal this Text or Code Snippet]]

2. Missing Return Statement

Inside the get_type method, if the loop does not find a matching pair, it reaches an end without returning a std::string. This also results in undefined behavior. To remedy this, ensure that your function returns a default value (like an empty string) if no match is found:

[[See Video to Reveal this Text or Code Snippet]]

3. Compiler Warnings

It's important to note that some modern compilers will issue warnings for such issues. If you see a warning during compilation, it’s crucial to address it, as the compiler may indicate a possible bug in your code.

Summary of the Fixes

Adjust Loop Index: Start your loop from 1 to avoid out-of-bounds access.

Return Defaults in Functions: Always ensure your functions return a value in all logical paths.

Pay Attention to Compiler Warnings: Treat compiler warnings seriously and use them as a guide to enhancing your code quality.

By implementing these changes, you will eliminate the free(): invalid pointer errors and enhance the stability and reliability of your C+ + programs.

Conclusion

Addressing runtime errors like the free(): invalid pointer is crucial to mastering C+ + . By learning how to diagnose and fix common errors in code, you become a more proficient programmer. Keep practicing and don't hesitate to ask for help whenever you face challenges. Happy coding!