C++ int64_t Type and Variable Declaration Conflicts

Resolving 'Conflicting Declaration' Errors with int64_t in C++

This article addresses a common C++ error: 'conflicting declaration'. We'll examine a scenario involving int64_t for memory calculations and provide a step-by-step solution.

Error Analysis

The error message 'conflicting declaration 'int free_int'' typically arises when you attempt to declare a variable with the same name within the same scope. This leads to ambiguity for the compiler.

Here's an example demonstrating the issue:c++std::cout << '--- int64_t type ---' << std::endl;int64_t free_int = static_cast<int64_t>(free_byte);int64_t total_int = static_cast<int64_t>(total_byte);int64_t free_int_g = free_int / 1024 / 1024 / 1024;int64_t total_int_g = total_int / 1024 / 1024 / 1024;std::cout << 'Total global memory: ' << total_int_g << 'G' << std::endl;std::cout << 'Total available memory: ' << free_int_g << 'G' << std::endl;

The Solution

The solution lies in ensuring unique variable names within a given scope. In our case, we can modify the variable name to resolve the conflict:c++std::cout << '--- int64_t type ---' << std::endl;int64_t free_int64 = static_cast<int64_t>(free_byte); // Modified variable nameint64_t total_int64 = static_cast<int64_t>(total_byte);int64_t free_int_g = free_int64 / 1024 / 1024 / 1024;int64_t total_int_g = total_int64 / 1024 / 1024 / 1024;std::cout << 'Total global memory: ' << total_int_g << 'G' << std::endl;std::cout << 'Total available memory: ' << free_int_g << 'G' << std::endl;

By renaming 'free_int' to 'free_int64', we eliminate the conflict, allowing the code to compile successfully.

Key Takeaway

Always choose descriptive and unique variable names to enhance code readability and prevent naming collisions in your C++ programs.