9. Release Notes

This following summarizes the most important changes in recent Spicy releases. For an exhaustive list of all changes, see the #CHANGES file coming with the distribution.

9.1. Version 1.9 (in progress)

New Functionality

Changed Functionality

Bug fixes

Documentation

9.2. Version 1.8

New Functionality

Add new skip keyword to let unit items efficiently skip over uninteresting data.

For cases where your parser just needs to skip over some data, without needing access to its content, Spicy provides a skip keyword to prefix corresponding fields with:
```
module Test;

public type Foo = unit {
    x: int8;
     : skip bytes &size=5;
    y: int8;
    on %done { print self; }
};
```
skip works for all kinds of fields but is particularly efficient with bytes fields, for which it will generate optimized code avoiding the overhead of storing any data.

skip fields may have conditions and hooks attached, like any other fields. However, they do not support $$ in expressions and hooks.

For readability, a skip field may be named (e.g., padding: skip bytes &size=3;), but even with a name, its value cannot be accessed.

skip fields extend support for void with attributes fields which are now deprecated.
Add runtime profiling infrastructure.

This add an option --enable-profiling to the HILTI and Spicy compilers. Use of the option does two things: (1) it sets a flag enabling inserting additional profiling instrumentation into generated C++ code, and (2) it enables using instrumentation for recording profiling information during execution of the compiled code, including dumping out a profiling report at the end. The profiling information collected includes time spent in HILTI functions as well as for parsing Spicy units and unit fields.

Changed Functionality

Optimizations for improved runtime performance.

This release contains a number of changes to improve the runtime performance of generated parsers. This includes tweaks for generating more performant code for parsers, low-level optimizations of types in to runtime support library as well as fine-tuning of parser execution at runtime.
Do not force locale on users of libhilti.
Avoid expensive checked iterator for internal Bytes iteration.
GH-1089: Allow to use offset() without enabling full random-access support.
GH-1394: Fix C++ normalization of generated enum values.
Disallow using $$ with anonymous containers.

Bug fixes

GH-1386: Prevent internal error when passed invalid context.
Fix potential use-after-move bug.
GH-1390: Initialize Bytes internal control block for all constructors.
GH-1396: Fix regex performance regression introduced by constant folding.
GH-1399: Guard access to unit _filters member with feature flag.
GH-1421: Store numerical offset in units instead of iterator for position.
GH-1436: Make sure Bytes::sub only throws HILTI exceptions.
GH-1447: Do not forcibly make strong_ref in function parameters immutable.
GH-1452: Allow resolving of unit parameters before self is fully resolved.
Make sure Spicy runtime config is initialized after spicy::rt::init.
Adjustments for building with GCC-13.

Documentation

Document how to check whether an optional value is set.
Preserve indention when extracting comments in doc generation.
Fix docs for long-form of -x flag to spicyc.

9.3. Version 1.7

New Functionality

Support Zeek-style documentation strings in Spicy source code.
Provide ability for host applications to initiate runtime’s module-pre-init phase manually.
Add DPD-style spicy::accept_input() and spicy::decline_input().
Add driver option to output full set of generated C++ files.
GH-1123: Support arbitrary expression as argument to type constructors, such as interval(...).

Changed Functionality

Search HILTI_CXX_INCLUDE_DIRS paths before default include paths.
Search user module paths before system paths.
Streamline runtime exception hierarchy.
Fix bug in cast from real to interval.
GH-1326: Generate proper runtime types for enums.
GH-1330: Reject uses of imported module IDs as expression.

Bug fixes

GH-1310: Fix ASAN false positive with GCC.
GH-1345: Improve runtime performance of stream iteration.
GH-1367: Use unique filename for all object files generated during JIT.
Remove potential race during JIT when using HILTI_CXX_COMPILER_LAUNCHER.
GH-1349: Fix incremental regexp matching for potentially empty results.

Documentation

9.4. Version 1.6

New Functionality

GH-1249: Allow combining &eod with &until or &until-including.
GH-1251: When decoding bytes into a string using a given character set, allow caller to control error handling.

All methods taking a charset parameters now take an additional enum selecting 1 of 3 possible error handling strategies in case a character can’t be decoded/represented: STRICT throws an error, IGNORE skips the problematic character and proceeds with the next, and REPLACE replaces the problematic character with a safe substitute. REPLACE is the default everywhere now, so that by default no errors are triggered.

This comes with an additional functional change for the ASCII encoding: we now consistently sanitize characters that ASCII can’t represent when in REPLACE/IGNORE modes (and, hence, by default), and trigger errors in STRICT mode. Previously, we’d sometimes let them through, and never triggered any errors. This also fixes a bug with the ASCII encoding sometimes turning a non-printable character into multiple repeated substitutes.
GH-1294: Add library function to parse an address from string or bytes.
HLTO files now perform a version check when loaded.

We previously would potentially allow building a HLTO file against one version of the Spicy runtime, and then load it with a different version. If exposed symbols matched loading might have succeeded, but could still have lead to sublte bugs at runtime.

We now embed a runtime version string in HLTO files and reject loading HLTO files into a different runtime version. We require an exact version match.
New pack and unpack operators.

These provide low-level primitives for transforming a value into, or out of, a binary representations, see the docs for details.

Changed Functionality

GH-1236: Add support for adding link dependencies via --cxx-link.
GH-1285: C++ identifiers referenced in &cxxname are now automatically interpreted to be in the global namespace.
Synchronization-related debug messages are now logged to the spicy-verbose stream. We added logging of successful synchronization.
Downgrade required Flex version. We previously required at least flex-2.6.0; we can now build against flex-2.5.37.
Improve C++ caching during JIT.

We improved caching behavior via HILTI_CXX_COMPILER_LAUNCHER if the configuration of spicyc was changed without changing the C++ file produced during JIT.
hilti::rt::isDebugVersion has been removed.
The -O | --optimize flag has been removed from command line tools.

This was already a no-op without observable side-effects.
GH-1311: Reject use of context() unit method if unit does not declare a context with %context.
GH-1319: Unsupported unit variable attributes are now rejected.
GH-1299: Add validator for bitfield field ranges.
We now reject uses of self as an ID.
GH-1233: Reject key types for maps that can’t be sorted.
Fix validator for field &default expression types for constness.

When checking types of field &default expressions we previously would also consider their constness. This breaks e.g., cases where the used expression is not a LHS like the field the &default is defined for,
```
type X = unit {
    var x: bytes = b"" + a;
};
```
We now do not consider constness in the type check anymore. Since fields are never const this allows us to set a &default with constant expressions as well.

Bug fixes

GH-1231: Add special handling for potential advance failure in trial mode.
GH-1115, GH-1196: Explicitly type temporary value used by &max_size logic.
GH-1143, GH-1220: Add coercion on assignment for optionals that only differ in constness of their inner types.
GH-1230: Add coercion to default argument of map::get.
GH-1234, GH-1238: Fix assertions with anonymous struct constructor.
GH-1248: Fix stop for unbounded loop.
GH-1250: Fix internal errors when seeing unsupported character classes in regular expression.
GH-1170: Fix contexts not allowing being passed inout.
GH-1266: Fix wrong type for Spicy-side self expression.
GH-1261: Fix inability to access unit fields through self in &convert expressions.
GH-1267: Install only needed headers from bundled SafeInt library.
GH-1227: Fix code generation when a module’s file could be imported through different means.
GH-1273: Remove bundled code licensed under CPOL license.
GH-1303: Fix potentially late synchronization when jumping over gaps during synchronization.
Do not force gold linker with user-provided linker flags or when built as a CMake subproject.
Improve efficiency of startsWith for long inputs.

Documentation

The documentation now reflects Zeek package manager Spicy feature templates.
The documentation for bitfields was clarified.
Documentation for casts from integers to boolean was added.
We added documentation for how to expose custom C++ code in Spicy.
Update doc link to commits mailing list.
Clarify that %context can only be used in top-level units.
Clarify that &until consumes the delimiter.
GH-1240: Clarify docs on SPICY_VERSION.
Add FAQ item on source locations.
Add example for use of ?..

9.5. Version 1.5

New Functionality

GH-1179: Cap parallelism use for JIT background jobs.

During JIT, we would previously launch all compilation jobs in parallel. For projects using many modules this could have lead to resource contention which often forced users to use sequential compilation with HILTI_JIT_SEQUENTIAL. We now by default cap the number of parallel background jobs at the number of logical cores. This can be parameterized with the environment variable HILTI_JIT_PARALLELISM which for HILTI_JIT_PARALLELISM=1 reproduces HILTI_JIT_SEQUENTIAL.
GH-1134: Add support for synchronize-at and synchronize-after properties.

These unit properties allow specifying a literal which should be searched for during error recovery. If the respective unit is used as a synchronize point during error recovery, i.e., it is used as a field which is marked &synchronize, input resynchronization during error recovery will seek to the next position of this pattern in the input stream.
GH-1209: Provide error message to %error handler.

We now allow to optionally provide a string parameter with %error that will receive the associated error message:
```
on %error(msg: string) { print msg; }
```

Changed Functionality

GH-1184: Allow more cache hits if only a few modules are changed in multi-module compilation.
GH-1208: Incremental performance tweaks for JIT.
GH-1197: Make handling of sanitizer workarounds more granular.

Bug fixes

GH-1150: Preserve additional permissions from umask when generating HLTO files.
GH-1154: Add stringificaton of Map::value_type.
GH-1080: Reject constant declarations at non-global scope.
GH-1164: Make compiler plugin initialization explicit.
GH-1050: Update location when entering most parser methods.
GH-1187: Fix support for having multiple source modules of the same name.
GH-1197: Prevent too early integer overflow in pow.
GH-1201: Adjust removal of symlinks on install for DESTDIR.
GH-1203: Allow changing DESTDIR between configure and install time.
GH-1204: Remove potential use-after-move.
GH-1210: Prevent unnecessarily executable stack with GNU toolchain.
GH-1206: Fix detection of recursive dependencies.
GH-1217: Produce hilti::rt::Bool when casting to boolean.
GH-1224: Fix import segfault.

Documentation

GH-44: Update docs for spicy-plugin rename _Zeek::Spicy -> Zeek::Spicy.
GH-1183: Update docs for Discourse migration [skip CI].
GH-1205: Update Spicy docs for now being built into Zeek.

9.6. Version 1.4

New Functionality

Add support for recovery from parse errors or incomplete input

This release adds support for recovering from parse errors or incomplete input (e.g., gaps or partial connections). Grammars can denote unit synchronization points with a &synchronize attribute. If an error is encountered while extracting a previous fields, parsing will attempt to resynchronize the input at that point. The synchronization result needs to be checked and confirmed or rejected explicitly; a number of hooks are provided for that. See the docs for details.
Remove restriction that units used as sinks need to be public
Uses ccache for C++ compilation during JIT if Spicy itself was configured to use ccache

Spicy spends a considerable amount of JIT time compiling generated C++ code. This work can be cached if neither inputs nor any of the used flags have changed so that subsequent JIT runs can complete much faster.

We now automatically cache many C++ compilation artifacts with ccache if Spicy itself was configured with e.g., --with-hilti-compiler-launcher=ccache. This behavior can be controlled or disabled via the HILTI_CXX_COMPILER_LAUNCHER environment variable.

GH-842: Add Spicy support for struct initialization.
GH-1036: Support unit initialization through a struct constructor expression.

Changed Functionality

GH-1074: %random-access is now derived automatically from uses and declaring it explicitly has been deprecated.
GH-1072: Disallow enum declarations with non-unique values.

It is unclear what code should be generated when requested to convert an integer value to the following enum:
```
type E = enum {
    A = 1,
    B = 2,
    C = 1,
};
```
For 1 we could produce either E::A or E::C here.

Instead of allowing this ambiguity we now disallow enums with non-unique values.

Bug fixes

Prevent exception if cache directory is not readable.
Propagate failure from cmake up to ./configure.
GH-1030: Make sure types required for globals are declared before being used.
Fix potentially use-after-free in stringification of stream::View.
GH-1087: Make offset return correct value even before parsing of field.

Documentation

9.7. Version 1.3

New Functionality

Add optimizer removing unused %random-access or %filter functionality

If a unit has e.g., a %random-access attribute Spicy emits additional code to track and update offsets. If the %random-access functionality is not used this leads to unneeded code being emitted which causes unneeded overhead, both during JIT and during execution.

We now emit such feature-dependent code under a feature flag (effectively a global boolean constant) which is by default on. Additionally, we added an optimizer pass which detects whether a feature is used and can disable unused feature functionality (switching the feature flag to off), and can then remove unreachable code behind such disabled feature flags by performing basic constant folding.
Add optimizer pass removing unused sink functionality

By default any unit declared public can be used as a sink. To support sink behavior additional code is emitted and invoked at runtime, regardless of whether the unit is used as a sink or not.

We now detect unused sink functionality and avoid emitting it.
GH-934: Allow $$ in place of self in unit convert attributes.

Changed Functionality

GH-941: Allow use of units with all defaulted parameters as entry points.
We added precompilation support for libspicy.h.
Drop support for end-of-life Fedora 32, and add support for Fedora 34.

Bug fixes

Correctly handle lookups for NULL library symbols.
Use safe integers for size functions in the runtime library.
Make it possible to build on ARM64.
Fix building with gcc-11.

Documentation

9.8. Version 1.2

New Functionality

GH-913: Add support for switch-level &parse-at and &parse-from attributes inside a unit.
Add optimizer pass removing unimplemented functions and methods.

This introduces a global pass triggered after all individual input ASTs have been finalized, but before we generate any C++ code. We then strip out any unimplemented member functions (typically Spicy hooks), both their definitions as well as their uses.

In order to correctly handle previously generated C++ files which might have been generated with different optimization settings, we disallow optimizations if we detect that a C++ input file was generated by us.

Changed Functionality

Add validation of unit switch attributes. We previously silently ignored unsupported attributes; now errors are raised.
Remove configure option --build-zeek-plugin. Spicy no longer supports building the Zeek plugin/analyzers in-tree. This used to be available primarily for development purposes, but became challenging to maintain.
Add environment variable HILTI_CXX_INCLUDE_DIRS to specify additional C++ include directories when compiling generated code.
GH-940: Add runtime check for parsing progress during loops.

Bug fixes

Fix computation of unset locations.
Fix accidental truncating conversion in integer code.

Documentation

9.9. Version 1.1

New Functionality

GH-844: Add support for &size attribute to unit switch statement.
GH-26: Add %skip, %skip-pre and %skip-post properties for skipping input matching a regular expression before any further input processing takes place.
Extend library functionality provided by the spicy module:
- crc32_init()/crc32_add() compute CRC32 checksums.
- mktime() creates a time value from individual components.
- zlib_init() initializes a ZlibStream with a given window bits argument.
- Zlib now accepts a window bits parameter.
Add a new find() method to units for that searches for a bytes sequence inside their input data, forward or backward from a given starting position.
Add support for &chunked when parsing bytes data with &until or &until_including.
Add encode() method to string for conversion to bytes.
Extend parsing of void fields:
- Add support for &eod to skip all data until the end of the current input is encountered.
- Add support for &until to skip all data until a deliminator is encountered. The deliminator will be extracted from the stream before continuing.
Port Spicy to Apple silicon.
Add Dockerfile for OpenSUSE 15.2.

Changed Functionality

Reject void fields with names.
Lower minimum required Python version to 3.2.
GH-882: Lower minimum required Bison version to 3.0.

Bug fixes

GH-872: Fix missing normalization of enum label IDs.
GH-878: Fix casting integers to enums.
GH-889: Fix hook handling for anonymous void fields.
GH-901: Fix type resolution bug in &convert.
Fix handling of &size attribute for anonymous void fields.
Fix missing update to input position before running %done hook.
Add validation rejecting $$ in hooks not supporting it.
Make sure container sizes are runtime integers.
Fix missing operator<< for enums when generating debug code.
GH-917: Default-initialize forwarding fields without type arguments.

Documentation

GH-37: Add documentation on how to skip data with void fields.

9.10. Migrating from the old prototype

Below we summarize language changes in Spicy compared to the original research prototype. Note that some of the prototype’s more advanced functionality has not yet been ported to the new code base; see the corresponding list on GitHub for what’s still missing.

Changes:

Renamed export linkage to public.
Renamed %byteorder property to %byte-order.
Renamed &byteorder attribute to &byte-order.
Renamed &bitorder attribute to &bit-order.
All unit-level properties now need to conclude with a semicolon (e.g., %filter;).
Renamed &length attribute to &size.
Renamed &until_including attribute to &until-including.
Replaced &parse with separate &parse-from (taking a “bytes” instance) and &parse-at (taking a stream iterator) attributes.
Attributes no longer accept their arguments in parentheses, it now must <attr>=expr. (Before, both versions were accepted.)
uint<N> and int<N> are no longer accepted, use uintN/intN instead (which worked before already as well)
list<T> is no longer supported, use vector<T> instead.
New syntax for parsing sequences: Use x: int8[5] instead of x: vector<int8> &length=5. For lists of unknown size, use x: int8[]. When parsing sequences sub-units, use: x: Item[]; or, if further arguments/attributes are required, x: (Item(1,2,3))[]. (The latter syntax isn’t great, but the old syntax was ambiguous.)
New syntax for functions: function f(<params>) [: <result>] instead of <result> f(<params>)
Renamed runtime support module from Spicy to spicy (so use import spicy)
In units, variables are now initialized to default values by default. Previously, that was (inconsistently) happening only for variables of type sink. To revert to the old behaviour, add “&optional” to the variable.
Renamed type double to real.
Generally, types don’t coerce implicitly to bool anymore except in specific language contexts, such as in statements with boolean conditions.
Filters can now be implemented in Spicy itself. The pre-built filter::Base64Decode and filter::Zlib provide the base64 and zlib functionality of the previously built-in filters.
{unit,sink}::add_filter are renamed to {unit,sink}::connect_filter.
Enums don’t coerce to bool anymore, need to manually compare to Undef.
Coercion to bool now happens only in certain contexts, like if-conditions (similar to C++).
The sink method sequence has been renamed to sequence_number.
The effect of the sink method set_initial_sequence_number no longer persists when reconnecting a different unit to a sink.
&transient is no longer a supported unit field attribute. The same effect can now be achieved through an anonymous field (also see next point).
$$ can now be generally used in hooks to refer to the just parsed value. That’s particularly useful inside hooks for anonymous fields, including fields that previously were &transient (see above). Previously, “$$” worked only for container elements in foreach hooks (which still operates the same way).
Fields of type real are parsed with &type attribute (e.g., &type=Spicy::RealType::IEEE754_Double). They used to &precision attributes with a different enum type.
Assigning to unit fields and variables no longer triggers any hooks. That also means that hooks are generally no longer supported for variables (This is tricky to implement, not clear it’s worth the effort.)
When importing modules, module names are now case-sensitive.
When parsing vectors/lists of integers of a given length, use &count instead of &length.
Zeek plugin:
- Bro::dpd_confirm() has been renamed to zeek::confirm_protocol(). There’s also a corresponding zeek::reject_protocol().
- To auto-export enums to Zeek, they need to be declared public.