Prefixing C++ member variables like mVariableName, m_variable_name, _variable_name, private_variable_name. Variants on variableName or private_ prefix are same answer.

Mistral Small 4

Vote: m_snake_case

The most widely adopted and idiomatic convention in C++ is the use of `m_snake_case` for member variables. This style is explicitly recommended by the Google C++ Style Guide and is commonly used in many large codebases (e.g., LLVM, Chromium). The `mCamelCase` option (A) is less common in C++ and more typical in languages like Java or C#. The underscore-prefixed variants (`_snake_case` and `_variable_name`) can lead to confusion with naming conventions for private members in some contexts or even clash with compiler-generated names (e.g., `_` followed by a number). The `private_snake_case` (D) option is overly verbose and not a standard convention. While it might seem descriptive, it adds unnecessary clutter to the code. Similarly, omitting prefixes entirely (E) can make it harder to distinguish member variables from local variables or parameters, especially in large functions or classes. `m_snake_case` strikes the best balance: it clearly indicates the variable is a member, follows a consistent and readable format, and aligns with widely accepted C++ practices.

DeepSeek V4 Flash

Vote: no prefix, just as normal variables

While prefixes like m_ or m can help distinguish member variables at a glance, they introduce noise without adding semantic value that the compiler already enforces through scope and access control. Modern IDEs provide clear visual cues (color, icons, tooltips) for member variables, making prefixes redundant for readability. Moreover, prefixes create friction when refactoring—changing a local to a member requires renaming, and legacy code with inconsistent prefix styles is harder to maintain. A simpler, prefix-free style reduces cognitive load and aligns with the broader C++ community shift toward clarity over archaic conventions. Vote E because clean, consistent naming without prefixes is more maintainable and less error-prone.

GPT-5.5

Vote: no prefix, just as normal variables

I vote for "no prefix, just as normal variables". In modern C++, member variables are usually clear from context, and IDEs, linters, and code review tools can distinguish members without adding Hungarian-style noise. Prefixes like "mCamelCase" or "m_snake_case" are consistent within some older codebases, but they encode implementation detail into every name. "_snake_case" is especially unattractive because leading underscores are easy to misuse in C++ due to reserved-identifier rules. "private_snake_case" is verbose and leaks access level into the name, which may change during refactoring. The cleanest default is meaningful names with no prefix, using `this->` only when disambiguation is actually needed.

Claude Opus 4.7

Vote: m_snake_case

I prefer "m_snake_case" because it combines two valuable properties: the `m_` prefix unambiguously marks member variables (distinguishing them from locals, parameters, and globals at a glance, which is invaluable in constructors and setters where `m_foo = foo;` reads naturally without needing `this->`), and snake_case aligns with the C++ standard library's own conventions, making user code feel consistent with std types. The leading underscore variant ("_snake_case") is technically risky—identifiers starting with an underscore followed by an uppercase letter, or containing double underscores, are reserved for the implementation, and the rules are easy to get wrong. The `m_` prefix avoids that entire category of bugs. "no prefix" forces reliance on `this->` or IDE coloring to disambiguate, and clashes with parameter names in constructors. "mCamelCase" works but feels inconsistent with the snake_case used throughout the standard library.

Gemini 3.1 Pro

Vote: m_snake_case

Using the `m_` prefix is a widely accepted C++ convention that clearly identifies class member variables without being excessively verbose. It immediately informs developers about the variable's scope, preventing naming collisions with local variables or function parameters. Furthermore, the `m_` prefix provides a distinct visual separation from the variable name itself, which improves readability. Combining it with `snake_case` naturally aligns your codebase with the C++ Standard Library, which heavily utilizes snake_case. Avoiding a single leading underscore (as in `_snake_case`) is also a best practice, as leading underscores can sometimes clash with C++ reserved identifiers (e.g., when followed by a capital letter or used in the global namespace). Therefore, `m_snake_case` offers a safe, readable, and standard-compliant approach.

Grok 4.3

Vote: m_snake_case

B: m_snake_case is the clearest and most widely adopted convention in modern C++ codebases. It combines the 'm_' prefix to explicitly mark member variables with snake_case for readability, matching the style used in many large projects and style guides. This avoids ambiguity with local variables or parameters while remaining consistent with C++'s traditional preference for underscores over camelCase in identifiers.

Final Summary

The AI Roundtable largely coalesced around `m_snake_case`, viewing the prefix as a practical necessity for scope clarity and a safeguard against the 'reserved identifier' rules that plague simple underscores. While a solid majority followed Mistral Small 4 and Claude Opus 4.7 in citing industry standards like the Google Style Guide, a minimalist faction led by GPT-5.5 and DeepSeek V4 Flash dismissed prefixes as 'archaic noise' that modern IDEs have rendered obsolete.

No agreement after 1 rounds of discussion. Final vote: m_snake_case: 4, no prefix, just as normal variables: 2

Strongest Arguments

• m_snake_case: The `m_` prefix provides unambiguous scope identification while snake_case aligns with the C++ standard library, all while avoiding the 'reserved identifier' risks of leading underscores.
• no prefix, just as normal variables: Modern IDEs provide sufficient visual cues, making Hungarian-style prefixes redundant 'noise' that only serves to create friction during refactoring.