How can you guarantee the absence of exceptions in…

Guaranteeing the complete absence of exceptions in C/C++ is challenging, but it is possible to minimize their likelihood and ensure reliable handling:

Use a restricted subset of the language:
- Avoid mechanisms that generate exceptions (e.g., new on memory shortage if new_handler is not set).
- Prefer RAII for resource management, which helps prevent leaks even in the case of exceptions.
- Use alternative error signaling methods such as:
  - Return codes (integer status codes).
  - Special return values (e.g., nullptr for pointers, std::optional).
  - Passing a reference to a variable for status recording (bool process(..., ErrorStatus& status)).
Static code analysis:
- Use tools like Clang-Tidy, cppcheck to identify potential issues before runtime.
Careful resource management (RAII):
- Use smart pointers (std::unique_ptr, std::shared_ptr) for automatic memory release.
- Wrap other resources (files, mutexes) in classes with destructors that guarantee release.

#include <fstream>
#include <iostream>

class FileGuard {
public:
    FileGuard(const std::string& filename) : file_(filename) {
        if (!file_.is_open()) {
            // In a context of exception absence guarantee,
            // return error code or other mechanism here.
            // For demonstration, just output an error.
            std::cerr << "Failed to open file\n";
        }
    }

    ~FileGuard() {
        if (file_.is_open()) {
            file_.close();
        }
    }

    // Disable copy and move to ensure unique ownership
    FileGuard(const FileGuard&) = delete;
    FileGuard& operator=(const FileGuard&) = delete;

    // Methods to work with file
    std::fstream& get() { return file_; }

private:
    std::fstream file_;
};

// Usage example:
// void process_file(const std::string& filename) {
//     FileGuard fg(filename);
//     if (fg.get().is_open()) {
//         // Work with file...
//     }
//     // File will be closed automatically on scope exit
// }

Contract programming and checks:
- Use assert to check invariants and pre/post-conditions in debug builds.
- Validate function input parameters.

#include <cassert>

int divide(int a, int b) {
    assert(b != 0); // Precondition check
    if (b == 0) {
        // In absence of exceptions:
        // return error code or other mechanism
        return 0; // Example return value
    }
    return a / b;
}

Thorough testing:
- Write comprehensive unit, integration, and stress tests to identify errors.
Use exceptions only for exceptional situations:
- (Although the question is about exception absence, it's important to understand that they can be used, but should be avoided strictly.) If exceptions are used, they should be limited and well-managed.
Memory allocation control:
- Use pool allocators or static buffers in critical sections or real-time systems to avoid std::bad_alloc.
Avoid functions that may throw exceptions (e.g., from the standard library) if their safe use in the context is not guaranteed.

Complete absence of exceptions often requires significant restrictions on language features and standard library usage, typical in real-time, embedded, or high-reliability code (MISRA C++). In most standard C++ applications, exceptions are a legitimate error handling mechanism, but their use should be well thought out and have a clear strategy.

To guarantee no exceptions, simply do not call functions that throw and use alternative error handling methods.

How can you guarantee the absence of exceptions in your C/C++ code?