User Commands xstr(1)
NAME
xstr - extract strings from C programs to implement shared
strings
SYNOPSIS
xstr -c filename [-v] [-l array]
xstr [-l array]
xstr filename [-v] [-l array]
DESCRIPTION
xstr maintains a file called 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, which are most
useful if they are also read-only.
The command:
example% xstr -c filename
extracts 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 suf-
fixes 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 xstr space called xs.c can be
created by a command of the form:
example% 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.
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User Commands xstr(1)
xstr can also be used on a single file. A command:
example% xstr filename
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 the standard input when the argument
`-' is given. An appropriate command sequence for running
xstr after the C preprocessor is:
example% cc -E name.c xstr -c -
example% cc -c x.c
example% mv x.o name.o
xstr does not touch the file strings unless new items are
added; thus make(1S) can avoid remaking xs.o unless truly
necessary.
OPTIONS
-c filename Take C source text from filename.
-v Verbose: display a progress report indi-
cating where new or duplicate strings were
found.
-l array Specify the named array in program refer-
ences to abstracted strings. The default
array name is xstr.
FILES
strings data base of strings
x.c massaged C source
xs.c C source for definition of array "xstr*(rq
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User Commands xstr(1)
/tmp/xs* temp file when xstr filename doesn't touch
strings
ATRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
ATRIBUTE TYPE ATRIBUTE VALUE
Availability SUNWcsu
SEE ALSO
make(1S), attributes(5)
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 would do.
NOTES
Be aware that xstr indiscriminately replaces all strings
with expressions of the form &xstr[number] regardless of the
way the original C code might have used the string. For
example, you will encounter a problem with code that uses
sizeof() to determine the length of a literal string because
xstr will replace the literal string with a pointer that
most likely will have a different size than the string's. To
circumvent this problem:
o use strlen() instead of sizeof(); note that
sizeof() returns the size of the array (including
the null byte at the end), whereas strlen() doesn't
count the null byte. The equivalent of
sizeof("xxx") really is (strlen("xxx"))]1.
o use #define for operands of sizeof() and use the
define'd version. xstr ignores #define statements.
Make sure you run xstr on filename before you run
it on the preprocessor.
You will also encounter a problem when declaring an initial-
ized character array of the form
char x[] = "xxx";
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User Commands xstr(1)
xstr will replace xxx with an expression of the form
&xstr[number] which will not compile. To circumvent this
problem, use static char *x = "xxx" instead of static char
x[] = "xxx".
SunOS 5.11 Last change: 14 Sep 1992 4
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