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yych being set by YYPEEK () and then not used. #182

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pmetzger opened this issue Apr 10, 2017 · 8 comments
Closed

yych being set by YYPEEK () and then not used. #182

pmetzger opened this issue Apr 10, 2017 · 8 comments

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@pmetzger
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@pmetzger pmetzger commented Apr 10, 2017

Howdy! Using the clang static analyzer and re2c 0.16, I've found a few instances where the analyzer finds instances of yych = YYPEEK (); where yych is not subsequently used in the control path. Although benign as bugs go, I'd still like to help you fix it.

Not 100% sure how to build a minimizing test case, without which it will be hard for you to track down the bug. Is there a way to figure out from the goto labels in the generated code to particular regular expressions that triggered the construction of that part of the code?

@pmetzger pmetzger changed the title unused yych being set by YYPEEK () and then not used. yych being set by YYPEEK () and then not used. Apr 10, 2017
@skvadrik
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@skvadrik skvadrik commented Apr 10, 2017

You can build a minimal test case using --skeleton option: http://re2c.org/manual/features/skeleton/skeleton.html
All it needs is regular expressions (everything inside of /*!re2c ... */ blocks), all the interface code is generated automatically. You can make sure that skeleton program builds and still triggers the bug, then post your reduced example, command line and warning report here.

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@pmetzger
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@pmetzger pmetzger commented Apr 10, 2017

It seems to build! I'll try bisecting the code until I get a minimal instance.

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@pmetzger
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@pmetzger pmetzger commented Apr 10, 2017

Okay, it seems to work! I've produced what isn't quite a minimal instance but it retains all the original warnings I was getting from the clang static analyzer just in case they're somehow different versions of the bug.

Build the attached with:
re2c --bit-vectors --nested-ifs -W -Werror --input custom --skeleton -o test-skeleton.c test-skeleton.re

Then use scan-build or ccc-analyzer directly and you get:

test-skeleton.c:299:9: warning: Value stored to 'yych' is never read
yych = YYPEEK ();
^ ~~~~~~~~~
test-skeleton.c:320:9: warning: Value stored to 'yych' is never read
yych = YYPEEK ();
^ ~~~~~~~~~
test-skeleton.c:376:9: warning: Value stored to 'yych' is never read
yych = YYPEEK ();
^ ~~~~~~~~~
3 warnings generated.
scan-build: 3 bugs found.v

So far as I can tell, the errors are indeed correct.

I will attach test-skeleton.c directly just to make sure you have exactly the same one. (For some reason, github has insisted that I put .txt at the ends of the file names...)

test-skeleton.re.txt
test-skeleton.c.txt

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@skvadrik
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@skvadrik skvadrik commented Apr 10, 2017

Thank you for the detailed report!
The bug has already been fixed in devel branch (I don't recall it, but maybe there was a similar issue somewhere).

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@pmetzger
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@pmetzger pmetzger commented Apr 10, 2017

When is the next release version likely to be cut? It seems like there's a lot of good stuff queued up... :)

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@skvadrik
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@skvadrik skvadrik commented Apr 11, 2017

Quite a lot, more than a year of development.
Unfortunately the main change in the upcoming release requires some research: it involves a relatively novel algorithm with a few modifications of my own. I have to formalize the algorithm, and it takes me longer than expected.

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@pmetzger
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@pmetzger pmetzger commented Apr 11, 2017

Cool. Is there any way to cherry pick the fixes for some of the other bugs, or is that too hard to do because they're dependent on the new algorithm for generating the automaton?

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@skvadrik
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@skvadrik skvadrik commented Apr 11, 2017

I suppose it's hard. The whole codebase changed since the last release.
I hope it won't be too long until the next release (a month?), but I said the same thing half a year ago and new sub-problems keep showing up.

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@skvadrik skvadrik closed this Mar 19, 2019
netbsd-srcmastr pushed a commit to NetBSD/pkgsrc that referenced this issue Sep 20, 2020
2.0.3 (2020-08-22)
~~~~~~~~~~~~~~~~~~

- Fix issues when building re2c as a CMake subproject
  (`#302 <https://github.com/skvadrik/re2c/pull/302>`_:

- Final corrections in the SIMPA article "RE2C: A lexer generator based on
  lookahead-TDFA", https://doi.org/10.1016/j.simpa.2020.100027

2.0.2 (2020-08-08)
~~~~~~~~~~~~~~~~~~

- Enable re2go building by default.

- Package CMake files into release tarball.

2.0.1 (2020-07-29)
~~~~~~~~~~~~~~~~~~

- Updated version for CMake build system (forgotten in release 2.0).

- Added a short article about re2c for the Software Impacts journal.

2.0 (2020-07-20)
~~~~~~~~~~~~~~~~

- Added new code generation backend for Go and a new ``re2go`` program
  (`#272 <https://github.com/skvadrik/re2c/issues/272>`_: Go support).
  Added option ``--lang <c | go>``.

- Added CMake build system as an alternative to Autotools
  (`#275 <https://github.com/skvadrik/re2c/pull/275>`_:
  Add a CMake build system (thanks to ligfx),
  `#244 <https://github.com/skvadrik/re2c/issues/244>`_: Switching to CMake).

- Changes in generic API:

  + Removed primitives ``YYSTAGPD`` and ``YYMTAGPD``.
  + Added primitives ``YYSHIFT``, ``YYSHIFTSTAG``, ``YYSHIFTMTAG``
    that allow to express fixed tags in terms of generic API.
  + Added configurations ``re2c:api:style`` and ``re2c:api:sigil``.
  + Added named placeholders in interpolated configuration strings.

- Changes in reuse mode (``-r, --reuse`` option):

  + Do not reset API-related configurations in each `use:re2c` block
    (`#291 <https://github.com/skvadrik/re2c/issues/291>`_:
    Defines in rules block are not propagated to use blocks).
  + Use block-local options instead of last block options.
  + Do not accumulate options from rules/reuse blocks in whole-program options.
  + Generate non-overlapping YYFILL labels for reuse blocks.
  + Generate start label for each reuse block in storable state mode.

- Changes in start-conditions mode (``-c, --start-conditions`` option):

  + Allow to use normal (non-conditional) blocks in `-c` mode
    (`#263 <https://github.com/skvadrik/re2c/issues/263>`_:
    allow mixing conditional and non-conditional blocks with -c,
    `#296 <https://github.com/skvadrik/re2c/issues/296>`_:
    Conditions required for all lexers when using '-c' option).
  + Generate condition switch in every re2c block
    (`#295 <https://github.com/skvadrik/re2c/issues/295>`_:
    Condition switch generated for only one lexer per file).

- Changes in the generated labels:

  + Use ``yyeof`` label prefix instead of ``yyeofrule``.
  + Use ``yyfill`` label prefix instead of ``yyFillLabel``.
  + Decouple start label and initial label (affects label numbering).

- Removed undocumented configuration ``re2c🎏o``, ``re2c🎏output``.

- Changes in ``re2c🎏t``, ``re2c🎏type-header`` configuration:
  filename is now relative to the output file directory.

- Added option ``--case-ranges`` and configuration ``re2c🎏case-ranges``.

- Extended fixed tags optimization for the case of fixed-counter repetition.

- Fixed bugs related to EOF rule:

  + `#276 <https://github.com/skvadrik/re2c/issues/276>`_:
    Example 01_fill.re in docs is broken
  + `#280 <https://github.com/skvadrik/re2c/issues/280>`_:
    EOF rules with multiple blocks
  + `#284 <https://github.com/skvadrik/re2c/issues/284>`_:
    mismatched YYBACKUP and YYRESTORE
    (Add missing fallback states with EOF rule)

- Fixed miscellaneous bugs:

  + `#286 <https://github.com/skvadrik/re2c/issues/286>`_:
    Incorrect submatch values with fixed-length trailing context.
  + `#297 <https://github.com/skvadrik/re2c/issues/297>`_:
    configure error on ubuntu 18.04 / cmake 3.10

- Changed bootstrap process (require explicit configuration flags and a path to
  re2c executable to regenerate the lexers).

- Added internal options ``--posix-prectable <naive | complex>``.

- Added debug option ``--dump-dfa-tree``.

- Major revision of the paper "Efficient POSIX submatch extraction on NFA".

----
1.3x
----

1.3 (2019-12-14)
~~~~~~~~~~~~~~~~

- Added option: ``--stadfa``.

- Added warning: ``-Wsentinel-in-midrule``.

- Added generic API primitives:

  + ``YYSTAGPD``
  + ``YYMTAGPD``

- Added configurations:

  + ``re2c:sentinel = 0;``
  + ``re2c:define:YYSTAGPD = "YYSTAGPD";``
  + ``re2c:define:YYMTAGPD = "YYMTAGPD";``

- Worked on reproducible builds
  (`#258 <https://github.com/skvadrik/re2c/pull/258>`_:
  Make the build reproducible).

----
1.2x
----

1.2.1 (2019-08-11)
~~~~~~~~~~~~~~~~~~

- Fixed bug `#253 <https://github.com/skvadrik/re2c/issues/253>`_:
  re2c should install unicode_categories.re somewhere.

- Fixed bug `#254 <https://github.com/skvadrik/re2c/issues/254>`_:
  Turn off re2c:eof = 0.

1.2 (2019-08-02)
~~~~~~~~~~~~~~~~

- Added EOF rule ``$`` and configuration ``re2c:eof``.

- Added ``/*!include:re2c ... */`` directive and ``-I`` option.

- Added ``/*!header:re2c:on*/`` and ``/*!header:re2c:off*/`` directives.

- Added ``--input-encoding <ascii | utf8>`` option.

  + `#237 <https://github.com/skvadrik/re2c/issues/237>`_:
    Handle non-ASCII encoded characters in regular expressions
  + `#250 <https://github.com/skvadrik/re2c/issues/250>`_
    UTF8 enoding

- Added include file with a list of definitions for Unicode character classes.

  + `#235 <https://github.com/skvadrik/re2c/issues/235>`_:
    Unicode character classes

- Added ``--location-format <gnu | msvc>`` option.

  + `#195 <https://github.com/skvadrik/re2c/issues/195>`_:
    Please consider using Gnu format for error messages

- Added ``--verbose`` option that prints "success" message if re2c exits
  without errors.

- Added configurations for options:

  + ``-o --output`` (specify output file)
  + ``-t --type-header`` (specify header file)

- Removed configurations for internal/debug options.

- Extended ``-r`` option: allow to mix multiple ``/*!rules:re2c*/``,
  ``/*!use:re2c*/`` and ``/*!re2c*/`` blocks.

  + `#55 <https://github.com/skvadrik/re2c/issues/55>`_:
    allow standard re2c blocks in reuse mode

- Fixed ``-F --flex-support`` option: parsing and operator precedence.

  + `#229 <https://github.com/skvadrik/re2c/issues/229>`_:
    re2c option -F (flex syntax) broken
  + `#242 <https://github.com/skvadrik/re2c/issues/242>`_:
    Operator precedence with --flex-syntax is broken

- Changed difference operator ``/`` to apply before encoding expansion of
  operands.

  + `#236 <https://github.com/skvadrik/re2c/issues/236>`_:
    Support range difference with variable-length encodings

- Changed output generation of output file to be atomic.

  + `#245 <https://github.com/skvadrik/re2c/issues/245>`_:
    re2c output is not atomic

- Authored research paper "Efficient POSIX Submatch Extraction on NFA"
  together with Dr Angelo Borsotti.

- Added experimental libre2c library (``--enable-libs`` configure option) with
  the following algorithms:

  + TDFA with leftmost-greedy disambiguation
  + TDFA with POSIX disambiguation (Okui-Suzuki algorithm)
  + TNFA with leftmost-greedy disambiguation
  + TNFA with POSIX disambiguation (Okui-Suzuki algorithm)
  + TNFA with lazy POSIX disambiguation (Okui-Suzuki algorithm)
  + TNFA with POSIX disambiguation (Kuklewicz algorithm)
  + TNFA with POSIX disambiguation (Cox algorithm)

- Added debug subsystem (``--enable-debug`` configure option) and new debug
  options:

  + ``-dump-cfg`` (dump control flow graph of tag variables)
  + ``-dump-interf`` (dump interference table of tag variables)
  + ``-dump-closure-stats`` (dump epsilon-closure statistics)

- Added internal options:

  + ``--posix-closure <gor1 | gtop>`` (switch between shortest-path algorithms
    used for the construction of POSIX closure)

- Fixed a number of crashes found by American Fuzzy Lop fuzzer:

  + `#226 <https://github.com/skvadrik/re2c/issues/226>`_,
    `#227 <https://github.com/skvadrik/re2c/issues/227>`_,
    `#228 <https://github.com/skvadrik/re2c/issues/228>`_,
    `#231 <https://github.com/skvadrik/re2c/issues/231>`_,
    `#232 <https://github.com/skvadrik/re2c/issues/232>`_,
    `#233 <https://github.com/skvadrik/re2c/issues/233>`_,
    `#234 <https://github.com/skvadrik/re2c/issues/234>`_,
    `#238 <https://github.com/skvadrik/re2c/issues/238>`_

- Fixed handling of newlines:

  + correctly parse multi-character newlines CR LF in ``#line`` directives
  + consistently convert all newlines in the generated file to Unix-style LF

- Changed default tarball format from .gz to .xz.

  + `#221 <https://github.com/skvadrik/re2c/issues/221>`_:
    big source tarball

- Fixed a number of other bugs and resolved issues:

  + `#2 <https://github.com/skvadrik/re2c/issues/2>`_: abort
  + `#6 <https://github.com/skvadrik/re2c/issues/6>`_: segfault
  + `#10 <https://github.com/skvadrik/re2c/issues/10>`_:
    lessons/002_upn_calculator/calc_002 doesn't produce a useful example program
  + `#44 <https://github.com/skvadrik/re2c/issues/44>`_:
    Access violation when translating the attached file
  + `#49 <https://github.com/skvadrik/re2c/issues/49>`_:
    wildcard state \000 rules makes lexer behave weard
  + `#98 <https://github.com/skvadrik/re2c/issues/98>`_:
    Transparent handling of #line directives in input files
  + `#104 <https://github.com/skvadrik/re2c/issues/104>`_:
    Improve const-correctness
  + `#105 <https://github.com/skvadrik/re2c/issues/105>`_:
    Conversion of pointer parameters into references
  + `#114 <https://github.com/skvadrik/re2c/issues/114>`_:
    Possibility of fixing bug 2535084
  + `#120 <https://github.com/skvadrik/re2c/issues/120>`_:
    condition consisting of default rule only is ignored
  + `#167 <https://github.com/skvadrik/re2c/issues/167>`_:
    Add word boundary support
  + `#168 <https://github.com/skvadrik/re2c/issues/168>`_:
    Wikipedia's article on re2c
  + `#180 <https://github.com/skvadrik/re2c/issues/180>`_:
    Comment syntax?
  + `#182 <https://github.com/skvadrik/re2c/issues/182>`_:
    yych being set by YYPEEK () and then not used
  + `#196 <https://github.com/skvadrik/re2c/issues/196>`_:
    Implicit type conversion warnings
  + `#198 <https://github.com/skvadrik/re2c/issues/198>`_:
    no match for ‘operator!=’ in ‘i != std::vector<_Tp, _Alloc>::rend() [with _Tp = re2c::bitmap_t, _Alloc = std::allocator<re2c::bitmap_t>]()’
  + `#210 <https://github.com/skvadrik/re2c/issues/210>`_:
    How to build re2c in windows?
  + `#215 <https://github.com/skvadrik/re2c/issues/215>`_:
    A memory read overrun issue in s_to_n32_unsafe.cc
  + `#220 <https://github.com/skvadrik/re2c/issues/220>`_:
    src/dfa/dfa.h: simplify constructor to avoid g++-3.4 bug
  + `#223 <https://github.com/skvadrik/re2c/issues/223>`_:
    Fix typo
  + `#224 <https://github.com/skvadrik/re2c/issues/224>`_:
    src/dfa/closure_posix.cc: pack() tweaks
  + `#225 <https://github.com/skvadrik/re2c/issues/225>`_:
    Documentation link is broken in libre2c/README
  + `#230 <https://github.com/skvadrik/re2c/issues/230>`_:
    Changes for upcoming Travis' infra migration
  + `#239 <https://github.com/skvadrik/re2c/issues/239>`_:
    Push model example has wrong re2c invocation, breaks guide
  + `#241 <https://github.com/skvadrik/re2c/issues/241>`_:
    Guidance on how to use re2c for full-duplex command & response protocol
  + `#243 <https://github.com/skvadrik/re2c/issues/243>`_:
    A code generated for period (.) requires 4 bytes
  + `#246 <https://github.com/skvadrik/re2c/issues/246>`_:
    Please add a license to this repo
  + `#247 <https://github.com/skvadrik/re2c/issues/247>`_:
    Build failure on current Cygwin, probably caused by force-fed c++98 mode
  + `#248 <https://github.com/skvadrik/re2c/issues/248>`_:
    distcheck still looks for README
  + `#251 <https://github.com/skvadrik/re2c/issues/251>`_:
    Including what you use is find, but not without inclusion guards

- Updated documentation and website.
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