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  17 <H2><A NAME="SEC64" HREF="suif1_toc.html#TOC64">Function Types</A></H2>
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  27 The <CODE>TYPE_FUNC</CODE> operator is used with the <CODE>func_type</CODE> derived
  28 type class to describe the types of SUIF procedures.  A function type
  29 includes the type of the return value and optionally the types of the
  30 arguments as well.  The <CODE>return_type</CODE> and <CODE>set_return_type</CODE>
  31 methods access the return type field.  The type system itself places no
  32 restrictions on the return types, but the SUIF call and return
  33 instructions do.  See section <A HREF="suif1_35.html#SEC35">Call Instructions</A>
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  41 Most of the complexity of function types involves the arguments.
  42 Pointers to the argument types are stored in a dynamically-allocated
  43 array.  The number of arguments, and thus the size of the array, is
  44 stored in a field that can be accessed with the <CODE>num_args</CODE> and
  45 <CODE>set_num_args</CODE> methods.  The number of arguments can be changed at
  46 any time; if necessary the argument array will be reallocated.  The type
  47 of a particular argument can be retrieved with the <CODE>arg_type</CODE>
  48 method and set with the <CODE>set_arg_type</CODE> method.  The arguments are
  49 numbered beginning with zero.
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  53 Argument types are under the same restrictions as result types of
  54 instructions (see section <A HREF="suif1_26.html#SEC26">Result Types</A>) -- they must be object types with
  55 known, non-zero size.
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  62 Since functions can be declared in C without complete prototypes, a
  63 function type may not be able to include any information about the
  64 arguments.  This is indicated in a SUIF function type by the result of
  65 the <CODE>args_known</CODE> method.  This flag can be set with the
  66 <CODE>set_args_known</CODE> and <CODE>set_args_unknown</CODE> methods.  Setting
  67 <CODE>args_known</CODE> FALSE sets the argument count to zero and the
  68 <CODE>has_varargs</CODE> flag to FALSE.  Conversely, setting the argument
  69 count to a non-zero value or the <CODE>has_varargs</CODE> flag to TRUE sets
  70 the <CODE>args_known</CODE> flag to TRUE.
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  76 Some functions in C and other languages have a variable number of
  77 arguments.  The SUIF function types support this by keeping a flag to
  78 indicate if there may be additional arguments besides the ones that are
  79 explicitly listed.  The <CODE>has_varargs</CODE> and <CODE>set_varargs</CODE>
  80 methods access this flag.  Note that the <CODE>has_varargs</CODE> flag should
  81 not be used if nothing else is known about the arguments.
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