|Announcing Ox release 1.6 email@example.com (Tom Shields) (2019-05-17)|
|From:||Tom Shields <firstname.lastname@example.org>|
|Date:||Fri, 17 May 2019 17:01:34 -0500|
|Injection-Info:||gal.iecc.com; posting-host="news.iecc.com:2001:470:1f07:1126:0:676f:7373:6970"; logging-data="47753"; mail-complaints-to="email@example.com"|
|Keywords:||tools, parse, available|
|Posted-Date:||17 May 2019 18:15:11 EDT|
Ox version 1.6 is now available on SourceForge
Ox generalizes the function of Yacc in the way that an attribute
grammar generalizes a context-free grammar. Ordinary Yacc and Lex
specifications may be augmented with definitions of synthesized and
inherited attributes written in C syntax. Ox checks these
specifications for consistency and completeness, and generates from
them a program that builds and decorates attributed parse trees.
The user may specify postdecoration traversals for easy ordering of
side effects, such as code generation. Ox handles the tedious and
error-prone details of writing code for parse-tree management, so
its use eases problems of security and maintainability associated
with that aspect of translator development.
* Noteworthy changes in release 1.6 (17 May 2019)
The Ox "-t" command-line feature to automatically build and display a parse
tree is reimplemented to build an internal representation of a parse tree
visualization using the Graphviz cgraph library. The former implementation
was seriously broken for large parse trees. The Graphviz implementation
requires user-provided code (using Graphviz package capabilities) to either
layout, render and display the parse tree, or to serialize the internal
representation into the Graphviz DOT language external representation into a
text file for later processing. User-defined visual decoration can be added
to the default parse tree visualization generated by an evaluator using
capabilities of the Graphviz cgraph library.
** Bug fixes
Ox will now handle input text files using the DOS/Windows line break (CRLF)
and the old Mac line break (CR)
Corrected an Ox lexer rule that was passing some input file newline (LF)
characters directly to stdout
Corrected a segfault when `__purgeBuffer()' was called prior to initializing
the `struct bufferRec' parameter passed in
** Test suite
Corrected the Attribute Grammar in test cases bison-2.3-glr, bison-2.4-glr,
bison-3.x-glr, btyacc-decls, and byacc-bt-decls to make the hidden
dependencies on the global symbol table explicit
** Build system
The configure script new displays a configuration summary
The GPPL compiler will now build with the Boehm-Demers-Weiser Conservative
C/C++ Garbage Collector package (www.hboehm.info/gc), if specified in the
Both Ox and the GPPL compiler will now build with the Dmalloc Debug Malloc
Library (dmalloc.com), if specified in the configuration
** Bug fixes
Corrected a memory leak in Ox-generated evaluators: semantic stack heap data,
separate from the attributed AST tree node heap data, not reclaimed
Corrected a minor memory leak in Ox: heap allocated file name string extracted
from a "#line" directive not free'd in all cases
Corrected a segfault in Ox (Linux): if Ox built with libgc w/o libcord, heap
data allocated (with `malloc()') by the library function `vasprintf()' was
passed to `GC_free()'
Corrected a segfault in Ox (Solaris): heap allocatoin size `off by 1' error
** Test suite
Portability improvements (removed use of `basename' in run script)
** Build system
Added Dmalloc Debug Malloc Library (dmalloc.com) as a build option
Improved robustness & generality (option consistency checking,
** Attribute grammar evaluator skeleton
The generated evaluator framework has been refactored to work with
multiple Yacc compatible parser generators (`bison', `byacc', `btyacc',
`msta') in addition to the original AT&T `yacc'. This includes support
for the various non-LALR(1) parsing algorithms provided by these tools
(LR(k>1), GLR, backtracking), the `byacc' and `bison' pure parser skeleton
variants, and the `bison' push parser skeleton variant.
Incorporated patches from the Technical University of Vienna, Austria, by
Martin Kögler, Florian G. Plug, and Mihai Ghete to build Ox using `flex'.
Accept/pass-through (most) bison, byacc, btyacc, msta, and flex
specification %-directives; recognize those that impact generated code.
Accept C++ namespace IDs and template type specifiers in a `%token', etc,
Accept a larger subset of the C/C++ type syntax in attribute declarations,
including types and type qualifiers added in the C99 standard
Allow properly nested parenthesized expressions in macro actual
parameters, including C comma expressions, removing the requirement for
a trailing comma.
Generate `#line' directives in the Ox-generated lexer and parser
specifications. Disable this functionality at configuration-time, or at
run-time with a command-line option, if using lexer and/or parser
generators that do not accept `#line' directives.
Additional command-line options:
- specify the prefix for Ox-generated external names, replacing the
default "yyy" prefix, which enables linking multiple evaluators in a
- specify output file name prefixes, replacing the default "oxout" prefix
- specify that the lexer is intended for use with a bison or byacc pure
parser skeleton, generating indirection references to yylval in leaf
attribute evaluation code.
- opt out of generating `#line' directives
Eliminated fixed size tables in Ox and in Ox-generated evaluators.
Provided the `yyyinit()' function, which must be called prior to the first
call of the lexer by the parser to initialize Xwindows data structures if
the Ox "-t" command-line option is used. Invocation of `yyyinit()' is
added automatically to a generated Lex specification file, but must be
invoked by user-written code for a generic (non-Lex) handwritten lexer.
** Bug fixes
Corrected the Ox "-S" command-line option failure for generic (non-Lex)
Corrected multiple invocations of `fclose()' on a given output file; this
caused a segmentation fault or an infinite loop within `fclose()' in
different glibc Linux implementations.
Added an `atexit()' handler to cleanup temporary files otherwise left
dangling by an Ox abnormal exit from a C library function.
Corrected missing parameter in invocation to `genImmCrefForAttrbRef()'
exposed by the switch to use of Standard C function prototypes.
Revised User Reference Manual and manpage to match the current release.
** Test suite
Test cases were added that verify correctness of attribute evaluation with
the various non-LALR(1) parsing algorithms (LR(k>1), GLR, backtracking)
and the pure and push parser skeleton variants
A test case was added to verify that the `#line' directive correctly
tracks source lines from the original Ox input file in error messages.
** Build system
Implemented a GNU Automake generated Autoconf Build system, with
configure-time options to:
- choose a specific Lex and/or Yacc compatible generator, rather than the
tool found first by the configure script
- build a version of Ox with debugging or profiling enabled
- build a version of Ox with `#line' directives disabled
- use the Boehm-Demers-Weiser C/C++ Conservative Garbage Collector package
(www.hboehm.info/gc), if found by the configure script
Tested build portability across the macOS, Linux, Windows (Cygwin, Msys),
and Solaris development environments, including multiple version of
various C/C++ compilers multiple version of lex, yacc, flex, bison, byacc,
btyacc, and msta.
** Backward incompatible changes from release G1.04
The approach adopted by Ox to work across multiple Yacc compatible parser
generators via modification of the Yacc `%union' declaration (or
generation of a `%union' declaration, if one is not present) enables
portable use of the Yacc semantic value stack to manage the Ox semantic
Since Ox uses the Yacc `%union' mechanism, the semantic value type
definition mechanisms supported by Yacc in user-supplied code:
(1) #define YYSTYPE <C_type_specifier> (default: `int')
(2) typedef <C_type_specifier> YYSTYPE;
are not suported. Yacc grammar specifications that make use of one of
these two approaches to the definition of `YYSTYPE' will not work as-is
with Ox, but must be first modified to include a Yacc `%union'
declaration to make the semantic value type explicit.
The requirement for a trailing comma in macro formal and actual parameter
lists has been eliminated; trailing commas in these positions are no
The curses-based incremental tree construction display mechanism was
removed. The lookahead processing in the various Yacc compatible
variants - `msta' LR(k>1), `byacc' & `btyacc' backtracking, and `bison'
GLR - can buffer more than a single lookahead token. The terminal node
processing from release G1.04 only worked for the single token lookahead
case. This capability may be reintroduced in a future version.
Removed the `@prune' reserved word (the token wasn't actually passed from
the lexer to the parser in release G1.04) and the associated
implementation. The generated evaluator knows better than the author when
pruning is feasible.
Enabled the `@decorate' reserved word (the token wasn't actually passed
from the lexer to the parser in release G1.04). The `@decorate' directive
forces evaluation of attributes, which may be required for the
implementation of interactive evaluators.
Renamed `yyyerror()' to `yyyabort()'.
These command-line options are no longer relevant and have been removed:
"-aN" set structure-alignment size to N (no longer relevant)
"-C" print Copyright statment
"-I" ANSI/ISO C/C++ instead of K&R C source
"-T" generate curses-based code to display tree construction
"-U" print command-line usage summary (replaced by "--help")
"-XaN" change the size of an internal table in Ox
"-YaN" change the size of an internal table in the generated evaluator
"-YY" enable "-YaN" command-line option in generated evaluator
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