Question

A lot of C++ code uses syntactical conventions for marking up data members. Common examples include

• m_memberName for public members (where public members are used at all)
• _memberName for private members or all members

Others try to enforce using this->member whenever a data member is used.

In my experience, most larger code bases fail at applying such rules consistently.

In other languages, these conventions are far less widespread. I see it only occasionally in Java or C# code. I think I have never seen it in Ruby or Python code. Thus, there seems to be a trend with more modern languages to not use special markup for data members.

Is this convention still useful today in C++ or is it just an anachronism, especially as it is used so inconsistently across libraries? Haven’t the other languages shown that one can do without member prefixes?

Answer 1

You have to be careful with using a leading underscore. A leading underscore before a capital letter in a word is reserved.
For example:

_Foo

_L

are all reserved words while

_foo

_l

are not. There are other situations where leading underscores before lowercase letters are not allowed. In my specific case, I found the _L happened to be reserved by Visual C++ 2005 and the clash created some unexpected results.

I am on the fence about how useful it is to mark up local variables.

Here is a link about which identifiers are reserved:
What are the rules about using an underscore in a C++ identifier?