4.4BSD/usr/src/usr.bin/lex/Changes
Changes between 2.3 (full) release of 26May90 and 2.2 (alpha) release:
User-visible:
- A lone <<EOF>> rule (that is, one which is not qualified with
a list of start conditions) now specifies the EOF action for
*all* start conditions which haven't already had <<EOF>> actions
given. To specify an end-of-file action for just the initial
state, use <INITIAL><<EOF>>.
- -d debug output is now contigent on the global yy_flex_debug
being set to a non-zero value, which it is by default.
- A new macro, YY_USER_INIT, is provided for the user to specify
initialization action to be taken on the first call to the
scanner. This action is done before the scanner does its
own initialization.
- yy_new_buffer() has been added as an alias for yy_create_buffer()
- Comments beginning with '#' and extending to the end of the line
now work, but have been deprecated (in anticipation of making
flex recognize #line directives).
- It is now documented that flex interprets "^foo|bar" differently
from lex. flex interprets it as "match either a 'foo' or a 'bar',
providing it comes at the beginning of a line", whereas lex
interprets it as "match either a 'foo' at the beginning of a line,
or a 'bar' anywhere".
- It is now documented that flex initializes the global "yyin" on
the first call to the scanner, while lex initializes it at
compile-time.
- It is now documented that yy_switch_to_buffer() can be used
in the yywrap() macro/routine.
- The funky restrictions on when semi-colons could follow the
YY_NEW_FILE and yyless macros have been removed. They now
behave identically to functions.
Other changes:
- Prototypes and proper declarations of void routines have
been added to the flex source code, courtesy of Kevin B. Kenny.
- Routines dealing with memory allocation now use void* pointers
instead of char* - see Makefile for porting implications.
- Error-checking is now done when flex closes a file.
- Various lint tweaks were added to reduce the number of gripes.
- Makefile has been further parameterized to aid in porting.
- Support for SCO Unix added.
- A note has been added to flexdoc.1 mentioning work in progress
on modifying flex to generate straight C code rather than a
table-driven automaton, with an email address of whom to contact
if you are working along similar lines.
Changes between 2.2 Patch #3 (30Mar90) and 2.2 Patch #2:
- fixed bug which caused -I scanners to bomb
Changes between 2.2 Patch #2 (27Mar90) and 2.2 Patch #1:
- fixed bug writing past end of input buffer in yyunput()
- fixed bug detecting NUL's at the end of a buffer
Changes between 2.2 Patch #1 (23Mar90) and 2.2 (alpha) release:
- Makefile fixes: definition of MAKE variable for systems
which don't have it; installation of flexdoc.1 along with
flex.1; fixed two bugs which could cause "bigtest" to fail.
- flex.skel fix for compiling with g++.
- README and flexdoc.1 no longer list an out-of-date BITNET address
for contacting me.
- minor typos and formatting changes to flex.1 and flexdoc.1.
Changes between 2.2 (alpha) release of March '90 and previous release:
User-visible:
- Full user documentation now available.
- Support for 8-bit scanners.
- Scanners now accept NUL's.
- A facility has been added for dealing with multiple
input buffers.
- Two manual entries now. One which fully describes flex
(rather than just its differences from lex), and the
other for quick(er) reference.
- A number of changes to bring flex closer into compliance
with the latest POSIX lex draft:
%t support
flex now accepts multiple input files and concatenates
them together to form its input
previous -c (compress) flag renamed -C
do-nothing -c and -n flags added
Any indented code or code within %{}'s in section 2 is
now copied to the output
- yyleng is now a bona fide global integer.
- -d debug information now gives the line number of the
matched rule instead of which number rule it was from
the beginning of the file.
- -v output now includes a summary of the flags used to generate
the scanner.
- unput() and yyrestart() are now globally callable.
- yyrestart() no longer closes the previous value of yyin.
- C++ support; generated scanners can be compiled with C++ compiler.
- Primitive -lfl library added, containing default main()
which calls yylex(). A number of routines currently living
in the scanner skeleton will probably migrate to here
in the future (in particular, yywrap() will probably cease
to be a macro and instead be a function in the -lfl library).
- Hexadecimal (\x) escape sequences added.
- Support for MS-DOS, VMS, and Turbo-C integrated.
- The %used/%unused operators have been deprecated. They
may go away soon.
Other changes:
- Makefile enhanced for easier testing and installation.
- The parser has been tweaked to detect some erroneous
constructions which previously were missed.
- Scanner input buffer overflow is now detected.
- Bugs with missing "const" declarations fixed.
- Out-of-date Minix/Atari patches provided.
- Scanners no longer require printf() unless FLEX_DEBUG is being used.
- A subtle input() bug has been fixed.
- Line numbers for "continued action" rules (those following
the special '|' action) are now correct.
- unput() bug fixed; had been causing problems porting flex to VMS.
- yymore() handling rewritten to fix bug with interaction
between yymore() and trailing context.
- EOF in actions now generates an error message.
- Bug involving -CFe and generating equivalence classes fixed.
- Bug which made -CF be treated as -Cf fixed.
- Support for SysV tmpnam() added.
- Unused #define's for scanner no longer generated.
- Error messages which are associated with a particular input
line are now all identified with their input line in standard
format.
- % directives which are valid to lex but not to flex are
now ignored instead of generating warnings.
- -DSYS_V flag can now also be specified -DUSG for System V
compilation.
Changes between 2.1 beta-test release of June '89 and previous release:
User-visible:
- -p flag generates a performance report to stderr. The report
consists of comments regarding features of the scanner rules
which result in slower scanners.
- -b flag generates backtracking information to lex.backtrack.
This is a list of scanner states which require backtracking
and the characters on which they do so. By adding rules
one can remove backtracking states. If all backtracking states
are eliminated, the generated scanner will run faster.
Backtracking is not yet documented in the manual entry.
- Variable trailing context now works, i.e., one can have
rules like "(foo)*/[ \t]*bletch". Some trailing context
patterns still cannot be properly matched and generate
error messages. These are patterns where the ending of the
first part of the rule matches the beginning of the second
part, such as "zx*/xy*", where the 'x*' matches the 'x' at
the beginning of the trailing context. Lex won't get these
patterns right either.
- Faster scanners.
- End-of-file rules. The special rule "<<EOF>>" indicates
actions which are to be taken when an end-of-file is
encountered and yywrap() returns non-zero (i.e., indicates
no further files to process). See manual entry for example.
- The -r (reject used) flag is gone. flex now scans the input
for occurrences of the string "REJECT" to determine if the
action is needed. It tries to be intelligent about this but
can be fooled. One can force the presence or absence of
REJECT by adding a line in the first section of the form
"%used REJECT" or "%unused REJECT".
- yymore() has been implemented. Similarly to REJECT, flex
detects the use of yymore(), which can be overridden using
"%used" or "%unused".
- Patterns like "x{0,3}" now work (i.e., with lower-limit == 0).
- Removed '\^x' for ctrl-x misfeature.
- Added '\a' and '\v' escape sequences.
- \<digits> now works for octal escape sequences; previously
\0<digits> was required.
- Better error reporting; line numbers are associated with rules.
- yyleng is a macro; it cannot be accessed outside of the
scanner source file.
- yytext and yyleng should not be modified within a flex action.
- Generated scanners #define the name FLEX_SCANNER.
- Rules are internally separated by YY_BREAK in lex.yy.c rather
than break, to allow redefinition.
- The macro YY_USER_ACTION can be redefined to provide an action
which is always executed prior to the matched rule's action.
- yyrestart() is a new action which can be used to restart
the scanner after it has seen an end-of-file (a "real" one,
that is, one for which yywrap() returned non-zero). It takes
a FILE* argument indicating a new file to scan and sets
things up so that a subsequent call to yylex() will start
scanning that file.
- Internal scanner names all preceded by "yy_"
- lex.yy.c is deleted if errors are encountered during processing.
- Comments may be put in the first section of the input by preceding
them with '#'.
Other changes:
- Some portability-related bugs fixed, in particular for machines
with unsigned characters or sizeof( int* ) != sizeof( int ).
Also, tweaks for VMS and Microsoft C (MS-DOS), and identifiers all
trimmed to be 31 or fewer characters. Shortened file names
for dinosaur OS's. Checks for allocating > 64K memory
on 16 bit'ers. Amiga tweaks. Compiles using gcc on a Sun-3.
- Compressed and fast scanner skeletons merged.
- Skeleton header files done away with.
- Generated scanner uses prototypes and "const" for __STDC__.
- -DSV flag is now -DSYS_V for System V compilation.
- Removed all references to FTL language.
- Software now covered by BSD Copyright.
- flex will replace lex in subsequent BSD releases.