5.11 Function Types

Various types can be defined for function variables. These types are not used in defining functions (see Procedures); they are used for things like pointers to functions.

The simple, traditional, type is type descriptor ‘f’ is followed by type information for the return type of the function, followed by a semicolon.

This does not deal with functions for which the number and types of the parameters are part of the type, as in Modula-2 or ANSI C. AIX provides extensions to specify these, using the ‘f’, ‘F’, ‘p’, and ‘R’ type descriptors.

First comes the type descriptor. If it is ‘f’ or ‘F’, this type involves a function rather than a procedure, and the type information for the return type of the function follows, followed by a comma. Then comes the number of parameters to the function and a semicolon. Then, for each parameter, there is the name of the parameter followed by a colon (this is only present for type descriptors ‘R’ and ‘F’ which represent Pascal function or procedure parameters), type information for the parameter, a comma, 0 if passed by reference or 1 if passed by value, and a semicolon. The type definition ends with a semicolon.

For example, this variable definition:

int (*g_pf)();

generates the following code:

.stabs "g_pf:G24=*25=f1",32,0,0,0
    .common _g_pf,4,"bss"

The variable defines a new type, 24, which is a pointer to another new type, 25, which is a function returning int.