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     XSTR(8)                                                   XSTR(8)

          xstr - preprocessor for sharing strings in C programs

          xstr [ -c ] [ - ] [ file ]

          Xstr maintains a file strings into which strings in compo-
          nent parts of a large program are hashed.  These strings are
          replaced with references to this common area.  This serves
          to implement shared constant strings, most useful if they
          are also read-only.

          The command

               xstr -c name

          will extract the strings from the C source in name, replac-
          ing string references by expressions of the form
          (&xstr[number]) for some number.  An appropriate declaration
          of xstr is prepended to the file.  The resulting C text is
          placed in the file x.c, to then be compiled.  The strings
          from this file are placed in the strings data base if they
          are not there already.  Repeated strings and strings which
          are suffices of existing strings do not cause changes to the
          data base.

          After all components of a large program have been compiled a
          file xs.c declaring the common xstr space can be created by
          a command of the form


          This xs.c file should then be compiled and loaded with the
          rest of the program.  If possible, the array can be made
          read-only (shared) saving space and swap overhead.

          Xstr can also be used on a single file.  A command

               xstr name

          creates files x.c and xs.c as before, without using or
          affecting any strings file in the same directory.

          It may be useful to run xstr after the C preprocessor if any
          macro definitions yield strings or if there is conditional
          code which contains strings which may not, in fact, be
          needed.  Xstr reads from its standard input when the argu-
          ment `-' is given.  An appropriate command sequence for run-
          ning xstr after the C preprocessor is:

     XSTR(8)                                                   XSTR(8)

               cc -E name.c | xstr -c -
               cc -c x.c
               mv x.o name.o

          Xstr does not touch the file strings unless new items are
          added, thus make can avoid remaking xs.o unless truly neces-

          strings        Data base of strings
          x.c       Massaged C source
          xs.c      C source for definition of array `xstr'
          /tmp/xs*  Temp file when `xstr name' doesn't touch strings

          If a string is a suffix of another string in the data base,
          but the shorter string is seen first by xstr both strings
          will be placed in the data base, when just placing the
          longer one there will do.