XSTR(1-SysV)        RISC/os Reference Manual         XSTR(1-SysV)



NAME
     xstr - extract strings from C programs to implement shared
     strings

SYNOPSIS
     xstr [ -c ] [ - ] [ file ]

DESCRIPTION
     xstr maintains a file strings into which strings in com-
     ponent 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

          xstr

     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:




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XSTR(1-SysV)        RISC/os Reference Manual         XSTR(1-SysV)



          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-
     sary.

FILES
     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

SEE ALSO
     mkstr(1)

ERRORS
     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.

































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