C/C++ Programmer's Guide (G06.27+, H06.08+, J06.03+)

Considerations for the native compilers only:
• An _extensible function is limited to 31 parameters. If more are supplied an error
message is generated.
• _extensible and _variable are treated the same, _variable is a synonym for
_extensible
Considerations for the TNS compilers only:
• A function with no prototype declaration or definition under pragma OLDCALLS cannot
be _extensible.
Considerations for both the native and TNS compilers:
• _extensible and _variable attributes cannot be specified for the same function.
• C-style variable argument lists (...) are not allowed.
• An _extensible attribute cannot be specified for a function that passes a structure by
value.
• Returning structures by value is not allowed.
• For _extensible(n), an error is generated if n is greater than the number of formal
parameters.
• In C++ these guidelines apply:
_extensible functions can neither be overloaded nor have default parameters.◦
◦ _extensible cannot be specified on global function templates, that is, function
templates that are not members of a class.
◦ _extensible cannot be specified on template member functions, that is, the member
functions of a template class.
◦ _extensible cannot be used on class member functions of any class.
_extensible functions in C and C++ are equivalent to extensible procedures in TAL, pTAL,
and D-series Pascal. For further discussion of _extensible functions in C and C++, see
Chapter 9: System-Level Programming. For further discussion of declaring external routines that
are written in pTAL, TAL, or D-series Pascal and that are extensible, see Chapter 7:
Mixed-Language Programming for TNS Programs, or Chapter 8: Mixed-Language Programming
for TNS/R and TNS/E Native Programs.
_resident
causes the function code to remain in main memory for the duration of program execution.
The operating system does not swap pages of this code.
Considerations for both the native and TNS compilers:
• The _resident attribute is effective only for function definitions. It is ignored if it is given
for a function declaration and its corresponding function definition is not in the same
compilation unit.
• For C++, if you define a local class within a _resident function, all member functions
of this local class are implicitly declared to be _resident.
_variable
directs the compiler to treat all formal parameters of the function as though they were optional,
even if some parameters are required by your code.
58 C and C++ Extensions