-Changes between release 2.5.0 (xxDec93) and release 2.4.5:
+Changes between release 2.5.0.1 (05Dec94) and release 2.4.7:
+
+ - A new concept of "start condition" scope has been introduced.
+ A start condition scope is begun with:
+
+ <SCs>{
+
+ where SCs is a list of one or more start conditions. Inside
+ the start condition scope, every rule automatically has the
+ prefix <SCs> applied to it, until a '}' which matches the
+ initial '{'. So, for example:
+
+ <ESC>{
+ "\\n" return '\n';
+ "\\r" return '\r';
+ "\\f" return '\f';
+ "\\0" return '\0';
+ }
+
+ is equivalent to:
+
+ <ESC>"\\n" return '\n';
+ <ESC>"\\r" return '\r';
+ <ESC>"\\f" return '\f';
+ <ESC>"\\0" return '\0';
+
+ Start condition scopes may be nested.
+
+ - The new %option directive can be used in the first section of
+ a flex scanner to control scanner-generation options. Most
+ options are given simply as names, optionally preceded by the
+ word "no" (with no intervening whitespace) to negate their
+ meaning. Some are equivalent to flex flags, so putting them
+ in your scanner source is equivalent to always specifying
+ the flag (%option's take precedence over flags):
+
+ 7bit -7 option
+ 8bit -8 option
+ align -Ca option
+ backup -b option
+ batch -B option
+ c++ -+ option
+ caseful opposite of -i option (caseful is the default);
+ case-sensitive same as above
+ caseless -i option;
+ case-insensitive same as above
+ debug -d option
+ default opposite of -s option
+ ecs -Ce option
+ fast -F option
+ full -f option
+ interactive -I option
+ lex-compat -l option
+ meta-ecs -Cm option
+ perf-report -p option
+ read -Cr option
+ stdout -t option
+ verbose -v option
+ warn opposite of -w option (so use "%option nowarn" for -w)
+
+ array equivalent to "%array"
+ pointer equivalent to "%pointer" (default)
+
+ Some provide new features:
+
+ always-interactive generate a scanner which always
+ considers its input "interactive" (no call to isatty()
+ will be made when the scanner runs)
+ main supply a main program for the scanner, which
+ simply calls yylex(). Implies %option yywrap.
+ never-interactive generate a scanner which never
+ considers its input "interactive" (no call to isatty()
+ will be made when the scanner runs)
+ stack if set, enable start condition stacks (see below)
+ stdinit if unset ("%option nostdinit"), initialize yyin
+ and yyout statically to nil FILE* pointers, instead
+ of stdin and stdout
+ yywrap if unset ("%option noyywrap"), scanner does not
+ call yywrap() upon EOF but simply assumes there
+ are no more files to scan
+
+ Flex scans your rule actions to determine whether you use the
+ REJECT or yymore features (this is not new). Two %options can be
+ used to override its decision, either by setting them to indicate
+ the feature is indeed used, or unsetting them to indicate it
+ actually is not used:
+
+ reject
+ yymore
+
+ Two %option's take string-delimited values, offset with '=':
+
+ outfile="<name>" equivalent to -o<name>
+ prefix="<name>" equivalent to -P<name>
+
+ A number of %option's are available for lint purists who
+ want to suppress the appearance of unneeded routines in
+ the generated scanner. Each of the following, if unset,
+ results in the corresponding routine not appearing in the
+ generated scanner:
+
+ input, unput
+ yy_push_state, yy_pop_state, yy_top_state
+ yy_scan_buffer, yy_scan_bytes, yy_scan_string
+
+ You can specify multiple options with a single %option directive,
+ and multiple directives in the first section of your flex input file.
+
+ - The new function:
+
+ YY_BUFFER_STATE yy_scan_string( const char *str )
+
+ returns a YY_BUFFER_STATE (which also becomes the current input
+ buffer) for scanning the given string, which occurs starting
+ with the next call to yylex(). The string must be NUL-terminated.
+ A related function:
+
+ YY_BUFFER_STATE yy_scan_bytes( const char *bytes, int len )
+
+ creates a buffer for scanning "len" bytes (including possibly NUL's)
+ starting at location "bytes".
+
+ Note that both of these functions create and scan a *copy* of
+ the string/bytes. (This may be desirable, since yylex() modifies
+ the contents of the buffer it is scanning.) You can avoid the
+ copy by using:
+
+ YY_BUFFER_STATE yy_scan_buffer( char *base, yy_size_t size )
+
+ which scans in place the buffer starting at "base", consisting
+ of "size" bytes, the last two bytes of which *must* be
+ YY_END_OF_BUFFER_CHAR (these bytes are not scanned; thus, scanning
+ consists of base[0] through base[size-2], inclusive). If you
+ fail to set up "base" in this manner, yy_scan_buffer returns a
+ nil pointer instead of creating a new input buffer.
+
+ The type yy_size_t is an integral type to which you can cast
+ an integer expression reflecting the size of the buffer.
+
+ - Three new routines are available for manipulating stacks of
+ start conditions:
+
+ void yy_push_state( int new_state )
+
+ pushes the current start condition onto the top of the stack
+ and BEGIN's "new_state" (recall that start condition names are
+ also integers).
+
+ void yy_pop_state()
- - Snapshot for installation on ell.
+ pops the top of the stack and BEGIN's to it, and
- - Self-contained scanners (modulo yywrap()).
+ int yy_top_state()
- - Three new routines are available for manipulating stacks
- of start conditions: yy_push_state( int new_state ),
- void yy_pop_state(), and int yy_top_state().
+ returns the top of the stack without altering the stack's
+ contents.
+
+ The start condition stack grows dynamically and so has no built-in
+ size limitation. If memory is exhausted, program execution
+ is aborted.
+
+ To use start condition stacks, your scanner must include
+ a "%option stack" directive.
+
+ - The promised rewrite of the C++ FlexLexer class has not yet
+ been done. Support for FlexLexer is limited at the moment to
+ fixing show-stopper bugs, so, for example, the new functions
+ yy_scan_string() & friends are not available to FlexLexer
+ objects.
+
+ - The new macro
+
+ yy_set_interactive(is_interactive)
+
+ can be used to control whether the current buffer is considered
+ "interactive". An interactive buffer is processed more slowly,
+ but must be used when the scanner's input source is indeed
+ interactive to avoid problems due to waiting to fill buffers
+ (see the discussion of the -I flag in flexdoc). A non-zero value
+ in the macro invocation marks the buffer as interactive, a zero
+ value as non-interactive. Note that use of this macro overrides
+ "%option always-interactive" or "%option never-interactive".
+
+ yy_set_interactive() must be invoked prior to beginning to
+ scan the buffer.
+
+ - The new macro
+
+ yy_set_bol(at_bol)
+
+ can be used to control whether the current buffer's scanning
+ context for the next token match is done as though at the
+ beginning of a line (non-zero macro argument; makes '^' anchored
+ rules active) or not at the beginning of a line (zero argument,
+ '^' rules inactive).
+
+ - Related to this change, the mechanism for determing when a scan is
+ starting at the beginning of a line has changed. It used to be
+ that '^' was active iff the character prior to that at which the
+ scan started was a newline. The mechanism now is that '^' is
+ active iff the last token ended in a newline (or the last call to
+ input() returned a newline). For most users, the difference in
+ mechanisms is negligible. Where it will make a difference,
+ however, is if unput() or yyless() is used to alter the input
+ stream. When in doubt, use yy_set_bol().
+
+ - The new beginning-of-line mechanism involved changing some fairly
+ twisted code, so it may have introduced bugs - beware ...
+
+ - The macro YY_AT_BOL() returns true if the next token scanned from
+ the current buffer will have '^' rules active, false otherwise.
- Flex now generates #line directives relating the code it
produces to the output file; this means that error messages
- A new "-ooutput" option writes the generated scanner to "output".
If used with -t, the scanner is still written to stdout, but
- its internal #line directives use "output".
+ its internal #line directives (see previous item) use "output".
+
+ - When generating #line directives, filenames with embedded '\'s
+ have those characters escaped (i.e., turned into '\\'). This
+ feature helps with reporting filenames for some MS-DOS and OS/2
+ systems.
+
+ - You can now change the name "flex" to something else (e.g., "lex")
+ by redefining $(FLEX) in the Makefile.
+
+ - Two bugs (one serious) that could cause "bigcheck" to fail have
+ been fixed.
+
+ - A number of portability/configuration changes have been made
+ for easier portability.
+
+ - You can use "YYSTATE" in your scanner as an alias for YY_START
+ (for AT&T lex compatibility).
+
+ - input() now maintains yylineno.
+
+ - input() no longer trashes yytext.
+
+ - C++ FlexLexer objects now use the "cerr" stream to report -d output
+ instead of stdio.
+
+ - The -c flag now has its full glorious POSIX interpretation (do
+ nothing), rather than being interpreted as an old-style -C flag.
+
+ - Scanners generated using -l lex compatiblity now have the symbol
+ YY_FLEX_LEX_COMPAT #define'd.
+
+ - Documentation now clarifies that start conditions persist across
+ switches to new input files or different input buffers. If you
+ want to e.g., return to INITIAL, you must explicitly do so.
+
+ - Documentation now clarifies that you can pass a nil FILE* pointer
+ to yy_create_buffer() or yyrestart() if you've arrange YY_INPUT
+ to not need yyin.
+
+ - Documentation now clarifies that YY_BUFFER_STATE is a pointer to
+ an opaque "struct yy_buffer_state".
+
+ - Documentation now stresses that you gain the benefits of removing
+ backing-up states only if you remove *all* of them.
+
+ - More #ifdef chud has been added to the parser in attempt to
+ deal with bison's use of alloca().
+
+ - "make clean" no longer deletes emacs backup files (*~).
+
+ - Some memory leaks have been fixed.
+
+ - A bug was fixed in which dynamically-expanded buffers were
+ reallocated a couple of bytes too small.
+
+ - -S will not be going away.
+
+ - With the 2.6 release, I am considering dropping support for non-ANSI
+ C compilers (in particular, non-prototyping C compilers). If this
+ puts you in a panic, drop me a line at flex-ansi@ee.lbl.gov. If
+ your mail bounces with "no such user", then enough people have
+ already complained that I've rescinded my decision.
+
+
+Changes between release 2.4.7 (03Aug94) and release 2.4.6:
+
+ - Fixed serious bug in reading multiple files.
+
+ - Fixed bug in scanning NUL's.
+
+ - Fixed bug in input() returning 8-bit characters.
+
+ - Fixed bug in matching text with embedded NUL's when
+ using %array or lex compatibility.
+
+ - Fixed multiple invocations of YY_USER_ACTION when using '|'
+ continuation action.
+
+ - Minor prototyping fixes.
+
+Changes between release 2.4.6 (04Jan94) and release 2.4.5:
+
+ - Linking with -lfl no longer required if your program includes
+ its own yywrap() and main() functions. (This change will cause
+ problems if you have a non-ANSI compiler on a system for which
+ sizeof(int) != sizeof(void*) or sizeof(int) != sizeof(size_t).)
+ - The use of 'extern "C++"' in FlexLexer.h has been modified to
+ get around an incompatibility with g++'s header files.
Changes between release 2.4.5 (11Dec93) and release 2.4.4:
- The skeleton file is no longer opened at run-time, but instead
compiled into a large string array (thanks to John Gilmore and
friends at Cygnus). You can still use the -S flag to point flex
- at a different skeleton file, though if you use this option let
- me know, as I plan to otherwise do away with -S in the near
- future.
+ at a different skeleton file.
- flex no longer uses a temporary file to store the scanner's
actions.
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