XSTR(8) XSTR(8)
NAME
xstr - preprocessor for sharing strings in C programs
SYNOPSIS
xstr [ -c ] [ - ] [ file ]
DESCRIPTION
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
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:
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-
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
BUGS
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.