Dear Bison riders, There is already quite a large number of patches since Bison 3.4: 265 so far (3.0: 1225, 3.1: 252, 3.2: 297, 3.3: 255, 3.4: 209). Many of them are "invisible" and mostly related to refactoring and preparing forthcoming changes. But some of them have a very visible impact.
In particular the use of integral types has been revised in both the generator and the generated parsers (thanks to Paul Eggert). As a consequence small parsers have a smaller footprint, and very large automata are now possible with the default backend (yacc.c). There is one breaking change that somewhat worries me: in C++ positions moved from unsigned (for line and column numbers) to int. It might break some existing projects, and maybe not. We *need* to know! If it does break your project, then we will design some migration path. Otherwise, let's keep things simple. Please, torture this beta, and report your mileage! Cheers! ================================================================== Bison is a general-purpose parser generator that converts an annotated context-free grammar into a deterministic LR or generalized LR (GLR) parser employing LALR(1) parser tables. Bison can also generate IELR(1) or canonical LR(1) parser tables. Once you are proficient with Bison, you can use it to develop a wide range of language parsers, from those used in simple desk calculators to complex programming languages. Bison is upward compatible with Yacc: all properly-written Yacc grammars work with Bison with no change. Anyone familiar with Yacc should be able to use Bison with little trouble. You need to be fluent in C, C++ or Java programming in order to use Bison. Here is the GNU Bison home page: https://gnu.org/software/bison/ ================================================================== Here are the compressed sources: https://alpha.gnu.org/gnu/bison/bison-3.4.90.tar.gz (4.1MB) https://alpha.gnu.org/gnu/bison/bison-3.4.90.tar.xz (3.1MB) Here are the GPG detached signatures[*]: https://alpha.gnu.org/gnu/bison/bison-3.4.90.tar.gz.sig https://alpha.gnu.org/gnu/bison/bison-3.4.90.tar.xz.sig Use a mirror for higher download bandwidth: https://www.gnu.org/order/ftp.html [*] Use a .sig file to verify that the corresponding file (without the .sig suffix) is intact. First, be sure to download both the .sig file and the corresponding tarball. Then, run a command like this: gpg --verify bison-3.4.90.tar.gz.sig If that command fails because you don't have the required public key, then run this command to import it: gpg --keyserver keys.gnupg.net --recv-keys 0DDCAA3278D5264E and rerun the 'gpg --verify' command. This release was bootstrapped with the following tools: Autoconf 2.69 Automake 1.16.1 Flex 2.6.4 Gettext 0.19.8.1 Gnulib v0.1-2899-g56ca994d4 ================================================================== NEWS * Noteworthy changes in release 3.4.90 (2019-10-29) [beta] ** Backward incompatible changes Lone carriage-return characters (aka \r or ^M) in the grammar files are no longer treated as end-of-lines. This changes the diagnostics, and in particular their locations. In C++, line numbers and columns are now represented as 'int' not 'unsigned', so that integer overflow on positions is easily checkable via 'gcc -fsanitize=undefined' and the like. This affects the API for positions. ** Bug fixes In Java, %define api.prefix was ignored. It now behaves as expected. ** New features *** Lookahead correction in C++ Contributed by Adrian Vogelsgesang. The C++ deterministic skeleton (lalr1.cc) now supports LAC, via the %define variable parse.lac. *** Variable api.token.raw: Optimized token numbers (all skeletons) In the generated parsers, tokens have two numbers: the "external" token number as returned by yylex (which starts at 257), and the "internal" symbol number (which starts at 3). Each time yylex is called, a table lookup maps the external token number to the internal symbol number. When the %define variable api.token.raw is set, tokens are assigned their internal number, which saves one table lookup per token, and also saves the generation of the mapping table. The gain is typically moderate, but in extreme cases (very simple user actions), a 10% improvement can be observed. *** Diagnostics with insertion The diagnostics now display suggestion below the underlined source. Replacement for undeclared symbols are now also suggested. $ cat /tmp/foo.y %% list: lis '.' | $ bison -Wall foo.y foo.y:2.7-9: error: symbol 'lis' is used, but is not defined as a token and has no rules; did you mean 'list'? 2 | list: lis '.' | | ^~~ | list foo.y:2.16: warning: empty rule without %empty [-Wempty-rule] 2 | list: lis '.' | | ^ | %empty foo.y: warning: fix-its can be applied. Rerun with option '--update'. [-Wother] *** Diagnostics about long lines Quoted sources may now be truncated to fit the screen. For instance, on a 30-column wide terminal: $ cat foo.y %token FOO FOO FOO %% exp: FOO $ bison foo.y foo.y:1.34-36: warning: symbol FOO redeclared [-Wother] 1 | … FOO … | ^~~ foo.y:1.8-10: previous declaration 1 | %token FOO … | ^~~ foo.y:1.62-64: warning: symbol FOO redeclared [-Wother] 1 | … FOO | ^~~ foo.y:1.8-10: previous declaration 1 | %token FOO … | ^~~ *** Debug traces in Java The Java backend no longer emits code and data for parser tracing if the %define variable parse.trace is not defined. *** Generated parsers prefer signed integer types Bison skeletons now prefer signed to unsigned integer types when either will do, as the signed types are less error-prone and allow for better checking with 'gcc -fsanitize=undefined'. Also, the types chosen are now portable to unusual machines where char, short and int are all the same width. On non-GNU platforms this may entail including <limits.h> and (if available) <stdint.h> to define integer types and constants. *** Generated parsers use better types for states Stacks now use the best integral type for state numbers, instead of always using 15 bits. As a result "small" parsers now have a smaller memory footprint (they use 8 bits), and there is support for large automata (16 bits), and extra large (using int, i.e., typically 31 bits).
