Manual page for xstr(1)
xstr - extract strings from C programs to implement shared strings
maintains a file called
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, which are most useful
if they are also read-only.
example% xstr -c filename
extracts the strings from the C source in name, replacing
string references by expressions of the form
for some number. An appropriate declaration of
is prepended to the file. The resulting C text is placed in the file
to then be compiled. The strings from
this file are placed in the
data base if they are not there already.
Repeated strings and strings which are suffixes of existing strings
do not cause changes to the data base.
After all components of a large program have been compiled, a file
declaring the common
can be created by a command of the form:
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.
can also be used on a single file. A
example% xstr filename
as before, without using or affecting any
file in the same directory.
It may be useful to run
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.
reads from the standard input when the argument
An appropriate command sequence for running
after the C preprocessor
example% cc -E name.c | xstr -c -
example% cc -c x.c
example% mv x.o name.o
does not touch the file
unless new items are added; thus
can avoid remaking
unless truly necessary.
- -c filename
Take C source text from
Verbose: display a progress report indicating where new or
duplicate strings were found.
- -l array
Specify the named
in program references to abstracted strings. The default array
data base of strings
C source for definition of array ``xstr*(rq
temp file when
If a string is a suffix of another string in the data base,
but the shorter string is seen first by
both strings will be placed in the data base, when just
placing the longer one there would do.
Be aware that
indiscriminately replaces all strings with expressions of the
regardless of the way the original C code might have
used the string. For example, you will encounter a problem with
code that uses
to determine the length of a literal string because
will replace the literal string with a pointer that most
likely will have a different size than the string's.
To circumvent this problem:
returns the size of the array (including the null byte at the end), whereas
doesn't count the null byte. The equivalent of
for operands of
and use the
statements. Make sure you run
before you run it on the preprocessor.
You will also encounter a problem when declaring an
initialized character array of the form
char x = "xxx";
with an expression of the form
which will not compile. To circumvent this problem, use
static char *x = "xxx"
static char x = "xxx".
Created by unroff & hp-tools.
© by Hans-Peter Bischof. All Rights Reserved (1997).
Last modified 21/April/97