C/C++里面变量名的最大长度是多少？

since resource is limited and the implementations vary from

platform to platform, so the std provides implementation quantities

(Annex B) such as:

— Nesting levels of compound statements, iteration control structures, and selection control structures[256].

— Nesting levels of conditional inclusion [256].

— Pointer, array, and function declarators (in any combination) modifying an arithmetic, structure, union,

or incomplete type in a declaration [256].

— Nesting levels of parenthesized expressions within a full expression [256].

— Number of initial characters in an internal identifier or macro name [1024].

— Number of initial characters in an external identifier [1024].

— External identifiers in one translation unit [65536].

— Identifiers with block scope declared in one block [1 024].

— Macro identifiers simultaneously defined in one transation unit [65 536].

— Parameters in one function definition [256].

— Arguments in one function call [256].

— Parameters in one macro definition [256].

— Arguments in one macro invocation [256].

— Characters in one logical source line [65 536].

— Characters in a character string literal or wide string literal (after concatenation) [65 536].

— Size of an object [262 144].

— Nesting levels for #include files [256].

— Case labels for a switch statement (excluding those for any nested switch statements) [16 384].

— Data members in a single class, structure, or union [16 384].

— Enumeration constants in a single enumeration [4 096].

— Levels of nested class, structure, or union definitions in a single structdeclarationlist[256].

— Functions registered by atexit()[32].

— Direct and indirect base classes [16 384].

— Direct base classes for a single class [1 024].

— Members declared in a single class [4 096].

— Final overriding virtual functions in a class, accessible or not [16 384].

— Direct and indirect virtual bases of a class [1 024].

— Static members of a class [1 024].

— Friend declarations in a class [4 096].

— Access control declarations in a class [4 096].

— Member initializers in a constructor definition [6 144].

— Scope qualifications of one identifier [256].

— Nested external specifications [1 024].

— Template arguments in a template declaration [1 024].

— Recursively nested template instantiations [17].

— Handlers per try block [256].

— Throw specifications on a single function declaration [256].