xstr - extract strings from C programs to implement shared strings
xstr [ -v ] [ [ -c ] [ - ] [ file ]
Xstr maintains a file strings into which strings in component 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 -v flag makes xstr verbose.
xstr -c name
will extract the strings from the C source in name, replacing 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
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 argument `-' is given. An appropriate command sequence
for running xstr after the C preprocessor is:
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 necessary.
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.
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