diff --git a/ChangeLog b/ChangeLog index 488b2801..ba2b3af3 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,9 @@ +2010-12-19 Joel E. Denny + + doc: cleanup. + * NEWS (2.5): Try to sort entries according to how interesting + users might find them. + 2010-12-19 Joel E. Denny doc: cleanup. diff --git a/NEWS b/NEWS index 99814004..576d8cd5 100644 --- a/NEWS +++ b/NEWS @@ -157,14 +157,16 @@ Bison News LAC is an experimental feature. More user feedback will help to stabilize it. -** Unrecognized %code qualifiers are now errors not warnings. +** Grammar symbol names can now contain dashes: + + Consistently with directives (such as %error-verbose) and variables + (e.g. push-pull), grammar symbol names may include dashes in any + position, similarly to periods and underscores. This is GNU + extension over POSIX Yacc whose use is reported by -Wyacc, and + rejected in Yacc mode (--yacc). ** %define improvements: -*** Unrecognized variables are now errors not warnings. - -*** Multiple invocations for any variable is now an error not a warning. - *** Can now be invoked via the command line: Each of these command-line options @@ -210,45 +212,11 @@ Bison News %define api.push-pull push -** Grammar symbol names can now contain dashes: +*** Unrecognized variables are now errors not warnings. - Consistently with directives (such as %error-verbose) and variables - (e.g. push-pull), grammar symbol names may include dashes in any - position, similarly to periods and underscores. This is GNU - extension over POSIX Yacc whose use is reported by -Wyacc, and - rejected in Yacc mode (--yacc). +*** Multiple invocations for any variable is now an error not a warning. -** YYFAIL now produces warnings and Java parsers no longer implement it: - - YYFAIL has existed for many years as an undocumented feature of - deterministic parsers in C generated by Bison. More recently, it was - a documented feature of Bison's experimental Java parsers. As - promised in Bison 2.4.2's NEWS entry, any appearance of YYFAIL in a - semantic action now produces a deprecation warning, and Java parsers - no longer implement YYFAIL at all. For further details, including a - discussion of how to suppress C preprocessor warnings about YYFAIL - being unused, see the Bison 2.4.2 NEWS entry. - -** Temporary hack for adding a semicolon to the user action: - - Previously, Bison appended a semicolon to every user action for - reductions when the output language defaulted to C (specifically, when - neither %yacc, %language, %skeleton, or equivalent command-line - options were specified). This allowed actions such as - - exp: exp "+" exp { $$ = $1 + $3 }; - - instead of - - exp: exp "+" exp { $$ = $1 + $3; }; - - As a first step in removing this misfeature, Bison now issues a - warning when it appends a semicolon. Moreover, in cases where Bison - cannot easily determine whether a semicolon is needed (for example, an - action ending with a cpp directive or a braced compound initializer), - it no longer appends one. Thus, the C compiler might now complain - about a missing semicolon where it did not before. Future releases of - Bison will cease to append semicolons entirely. +** Unrecognized %code qualifiers are now errors not warnings. ** Character literals not of length one: @@ -263,44 +231,6 @@ Bison News Bison now warns when a character literal is not of length one. In some future release, Bison will start reporting an error instead. -** Verbose syntax error message fixes: - - When %error-verbose or `#define YYERROR_VERBOSE' is specified, - syntax error messages produced by the generated parser include the - unexpected token as well as a list of expected tokens. The effect - of %nonassoc on these verbose messages has been corrected in two - ways, but a complete fix requires LAC, described above: - -*** When %nonassoc is used, there can exist parser states that accept no - tokens, and so the parser does not always require a lookahead token - in order to detect a syntax error. Because no unexpected token or - expected tokens can then be reported, the verbose syntax error - message described above is suppressed, and the parser instead - reports the simpler message, "syntax error". Previously, this - suppression was sometimes erroneously triggered by %nonassoc when a - lookahead was actually required. Now verbose messages are - suppressed only when all previous lookaheads have already been - shifted or discarded. - -*** Previously, the list of expected tokens erroneously included tokens - that would actually induce a syntax error because conflicts for them - were resolved with %nonassoc in the current parser state. Such - tokens are now properly omitted from the list. - -*** Expected token lists are still often wrong due to state merging - (from LALR or IELR) and default reductions, which can both add - invalid tokens and subtract valid tokens. Canonical LR almost - completely fixes this problem by eliminating state merging and - default reductions. However, there is one minor problem left even - when using canonical LR and even after the fixes above. That is, - if the resolution of a conflict with %nonassoc appears in a later - parser state than the one at which some syntax error is - discovered, the conflicted token is still erroneously included in - the expected token list. Bison's new LAC implementation, - described above, eliminates this problem and the need for - canonical LR. However, LAC is still experimental and is disabled - by default. - ** Destructor calls fixed for lookaheads altered in semantic actions: Previously for deterministic parsers in C, if a user semantic action @@ -350,6 +280,76 @@ Bison News the user %code sections so that its #ifndef guard does not try to override the user's YYLLOC_DEFAULT if provided. +** YYFAIL now produces warnings and Java parsers no longer implement it: + + YYFAIL has existed for many years as an undocumented feature of + deterministic parsers in C generated by Bison. More recently, it was + a documented feature of Bison's experimental Java parsers. As + promised in Bison 2.4.2's NEWS entry, any appearance of YYFAIL in a + semantic action now produces a deprecation warning, and Java parsers + no longer implement YYFAIL at all. For further details, including a + discussion of how to suppress C preprocessor warnings about YYFAIL + being unused, see the Bison 2.4.2 NEWS entry. + +** Temporary hack for adding a semicolon to the user action: + + Previously, Bison appended a semicolon to every user action for + reductions when the output language defaulted to C (specifically, when + neither %yacc, %language, %skeleton, or equivalent command-line + options were specified). This allowed actions such as + + exp: exp "+" exp { $$ = $1 + $3 }; + + instead of + + exp: exp "+" exp { $$ = $1 + $3; }; + + As a first step in removing this misfeature, Bison now issues a + warning when it appends a semicolon. Moreover, in cases where Bison + cannot easily determine whether a semicolon is needed (for example, an + action ending with a cpp directive or a braced compound initializer), + it no longer appends one. Thus, the C compiler might now complain + about a missing semicolon where it did not before. Future releases of + Bison will cease to append semicolons entirely. + +** Verbose syntax error message fixes: + + When %error-verbose or `#define YYERROR_VERBOSE' is specified, + syntax error messages produced by the generated parser include the + unexpected token as well as a list of expected tokens. The effect + of %nonassoc on these verbose messages has been corrected in two + ways, but a complete fix requires LAC, described above: + +*** When %nonassoc is used, there can exist parser states that accept no + tokens, and so the parser does not always require a lookahead token + in order to detect a syntax error. Because no unexpected token or + expected tokens can then be reported, the verbose syntax error + message described above is suppressed, and the parser instead + reports the simpler message, "syntax error". Previously, this + suppression was sometimes erroneously triggered by %nonassoc when a + lookahead was actually required. Now verbose messages are + suppressed only when all previous lookaheads have already been + shifted or discarded. + +*** Previously, the list of expected tokens erroneously included tokens + that would actually induce a syntax error because conflicts for them + were resolved with %nonassoc in the current parser state. Such + tokens are now properly omitted from the list. + +*** Expected token lists are still often wrong due to state merging + (from LALR or IELR) and default reductions, which can both add + invalid tokens and subtract valid tokens. Canonical LR almost + completely fixes this problem by eliminating state merging and + default reductions. However, there is one minor problem left even + when using canonical LR and even after the fixes above. That is, + if the resolution of a conflict with %nonassoc appears in a later + parser state than the one at which some syntax error is + discovered, the conflicted token is still erroneously included in + the expected token list. Bison's new LAC implementation, + described above, eliminates this problem and the need for + canonical LR. However, LAC is still experimental and is disabled + by default. + * Changes in version 2.4.3 (2010-08-05): ** Bison now obeys -Werror and --warnings=error for warnings about