VMS::XSSymSet - keep sets of symbol names palatable to the VMS linker


  use VMS::XSSymSet;

  $set = new VMS::XSSymSet;
  while ($sym = make_symbol()) { $set->addsym($sym); }
  foreach $safesym ($set->all_trimmed) {
    print "Processing $safesym (derived from ",$self->get_orig($safesym),")\n";

  $safesym = VMS::XSSymSet->trimsym($onesym);


Since the VMS linker distinguishes symbols based only on the first 31 characters of their names, it is occasionally necessary to shorten symbol names in order to avoid collisions. (This is especially true of names generated by xsubpp, since prefixes generated by nested package names can become quite long.) VMS::XSSymSet provides functions to shorten names in a consistent fashion, and to track a set of names to insure that each is unique. While designed with xsubpp in mind, it may be used with any set of strings.

This package supplies the following functions, all of which should be called as methods.


Creates an empty VMS::XSSymset set of symbols. This function may be called as a static method or via an existing object. If $maxlen or $silent are specified, they are used as the defaults for maximum name length and warning behavior in future calls to addsym() or trimsym() via this object.


Creates a symbol name from $name, using the methods described under trimsym(), which is unique in this set of symbols, and returns the new name. $name and its resultant are added to the set, and any future calls to addsym() specifying the same $name will return the same result, regardless of the value of $maxlen specified. Unless $silent is true, warnings are output if $name had to be trimmed or changed in order to avoid collision with an existing symbol name. $maxlen and $silent default to the values specified when this set of symbols was created. This method must be called via an existing object.


Creates a symbol name $maxlen or fewer characters long from $name and returns it. If $name is too long, it first tries to shorten it by removing duplicate characters, then by periodically removing non-underscore characters, and finally, if necessary, by periodically removing characters of any type. $maxlen defaults to 31. Unless $silent is true, a warning is output if $name is altered in any way. This function may be called either as a static method or via an existing object, but in the latter case no check is made to insure that the resulting name is unique in the set of symbols.


Removes $name from the set of symbols, where $name is the original symbol name passed previously to addsym(). If $name existed in the set of symbols, returns its ``trimmed'' equivalent, otherwise returns undef. This method must be called via an existing object.


Returns the original name which was trimmed to $trimmed by a previous call to addsym(), or undef if $trimmed does not correspond to a member of this set of symbols. This method must be called via an existing object.


Returns the trimmed name which was generated from $name by a previous call to addsym(), or undef if $name is not a member of this set of symbols. This method must be called via an existing object.


Returns a list containing all of the original symbol names from this set.


Returns a list containing all of the trimmed symbol names from this set.


Charles Bailey <>


Last revised 14-Feb-1997, for Perl 5.004.


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