2 - Implementation quantities (informative) [limits]

-1- Because computers are finite, C++ implementations are inevitably limited in the size of the programs they can successfully process. Every implementation shall document those limitations where known. This documentation may cite fixed limits where they exist, say how to compute variable limits as a function of available resources, or say that fixed limits do not exist or are unknown.

-2- The limits may constrain quantities that include those described below or others. The bracketed number following each quantity is recommended as the minimum for that quantity. However, these quantities are only guidelines and do not determine compliance.

• 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 [1024].

• Macro identifiers simultaneously defined in one transation unit [65536].

• 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 [65536].

• Characters in a character string literal or wide string literal (after concatenation) [65536].

• Size of an object [262144].

• Nesting levels for #include files [256].

• Case labels for a switch statement (excluding those for any nested switch statements) [16384].

• Data members in a single class, structure, or union [16384].

• Enumeration constants in a single enumeration [4096].

• Levels of nested class, structure, or union definitions in a single struct-declaration-list [256].

• Functions registered by atexit()[32].

• Direct and indirect base classes [16384].

• Direct base classes for a single class [1024].

• Members declared in a single class [4096].

• Final overriding virtual functions in a class, accessible or not [16384].

• Direct and indirect virtual bases of a class [1024].

• Static members of a class [1024].

• Friend declarations in a class [4096].

• Access control declarations in a class [4096].

• Member initializers in a constructor definition [6144].

• Scope qualifications of one identifier [256].

• Nested external specifications [1024].

• Template arguments in a template declaration [1024].

• Recursively nested template instantiations [17].

• Handlers per try block [256].

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