NVC - VHDL Compiler and Simulator

Unreleased changes

Version 1.17.0 - 2025-07-12

• Updated to OSVVM 2025.02 and UVVM 2025.04.18 for nvc --install.
• Added --merge-mode option to control behaviour when merging non-equal coverage databases.
• generate statements now create separate hierarchy in the code coverage report
• Fixed "unit is too big to compile" error with very large number of signals (#1200).
• Just-in-time compilation is now the default and the --jit elaboration option has no effect. Use --precompile to restore the previous behaviour.
• Fixed a crash when set_cover_scope_name from nvc.cover_pkg was called with coverage disabled (#1218).
• Code coverage reports now contain the source files instead of referencing them (from @Blebowski).
• The --ieee-warnings option now supports off-at-0 to suppress warnings only in the first time step (from @supleed2).
• Top-level generics can now be set to hexadecimal values from the command line using -g name='X"12"'. The value must be escaped or quoted to avoid the double quotes being interpreted by the shell.
• Fixed a crash when ports with view mode indications are partially associated in a port map (#1208).
• Files declared in impure functions are now closed after the return expression has been evaluated rather than before (#1229).
• Added missing slice direction check at runtime (#1231).
• Several other minor bugs were resolved (#1220, #1233, #1234, #1239).

Version 1.16.2 - 2025-06-11

• Fixed a crash when an entity uses VHDL-2019 enhanced type generics and sub-elements of a port with a generic array type are associated individually (#1201).
• Fixed an issue where some generate statements were inaccessible from VHPI (#1213).
• Several other minor bugs were resolved (#1202, #1204, #1212).

Version 1.16.1 - 2025-05-12

• Fixed an elaboration failure where generic names differ in case between entity and component and the files were analysed with --preserve-case (#1195).
• Fixed a crash when expression coverage is enabled and a port is associated with a non-static expression (#1194).
• Fixed a debug assertion failure when initialising an array with more than 2**32 elements (#1196).
• Fixed a crash when concatenating unconstrained arrays of arrays (#1199).

Version 1.16.0 - 2025-04-21

• Added support for PSL prev(), stable(), rose() and fell() built-in functions (#1135).
• Signals can now be read and passed to subprograms during elaboration and the effective value is the default value associated with the signal. This behaviour is not defined by the LRM but matches all other simulators (#1144).
• MSYS2 binary packages are no longer provided with releases as these become out-of-date too quickly. Windows users should instead download the self-contained MSI package.
• The Ubuntu binary packages for releases now have predictable names without the git commit hash (#1131).
• Improved error messages when design units have circular dependencies or depend on obsolete design units (#1152).
• Toggle coverage count is displayed correctly for unreachable constant driven toggle bins and transitions from X are counted with --count-from-undefined instead of just U.
• Added an experimental --preserve-case analysis option to retain the original spelling of VHDL identifiers (#723).
• --ieee-warnings is now a global option and should be placed before the -r command. Passing it to the -r command is still supported but deprecated and may not take effect in some situations (#1151).
• Fixed a crash when a partial association in a port map has a conversion function (#1161).
• Improved the formatting of the --help output.
• The GitHub Action has been renamed from nickg/setup-nvc-ci to nickg/setup-nvc, although the old name should redirect to the new.
• A Docker image was added at ghcr.io/nickg/nvc (#1165).
• Unconstrained input ports can now be constrained by the result subtype of a conversion function (#1171).
• Type marks are now allowed in the prefix of selected names in relaxed mode (#1173).
• Added the nvc.random random number generation package and --seed argument for deterministic results.
• Added support for PSL union operator (from @Blebowski).
• The implementation of concatenations has been reworked fixing several bugs (#1178).
• Added support for conditional force assignment (#1185).
• Access and file types are now supported in VHPI (#1192).
• Fixed a crash when open actual was used for formal parameter without default.
• Several other minor bugs were resolved (#1174, #1159, #1177, #1191, #1188).

Version 1.15.2 - 2025-03-01

• Fixed invalid LLVM IR generation which could cause a crash with LLVM 14 (#1145).
• Functional coverage is now reported correctly when summing from nested hierarchies (#1154).
• External names can now be the target of concurrent signal assignment statements (#1156).
• Fixed a crash when packages are passed through multiple layers of generics.
• Fixed a crash when a record subtype has a partially constrained element (#1155).
• Fixed wrong result of VHDL-2019 std.env.file_path when the source file was analysed using a relative path (#1162).
• Fixed a crash when 'last_event or 'last_active is used with a record type (#1164).

Version 1.15.1 - 2025-01-22

• Fixed a crash when a subprogram is called with too many named arguments (from @NikLeberg) (#1091).
• Fixed a crash when a constant record aggregate has a null array element (#1137).
• Fixed a regression that caused some array aggregates to be incorrectly reported as ambiguous (#1138).
• The Windows installer now bundles the Tcllib library (#1136).
• Fixed a bug where PSL directives in comments were parsed incorrectly when split over multiple lines (#1135).

Version 1.15.0 - 2025-01-11

• --load is now a global option and should be placed before the -r command. This allows VHPI foreign subprograms to be called during elaboration (#988).
• The --per-file coverage report option outputs code coverage reports for each source file instead of each instance (#823).
• The new --check-synthesis analysis option warns when signals are missing from process sensitivity lists.
• Fixed a crash when a generic subprogram is associated with open (#1025).
• Added a functional coverage API in nvc.cover_pkg that can be used by external frameworks such as OSVVM to define cover points.
• Added threshold-<value> option for coverage to set minimal count a coverage bin must reach to be reported as covered.
• Added a warning for potential infinite loops in processes without sensitivity and lacking any wait statements (from @NikLeberg).
• Selected names can now be to register value change callbacks with vhpi_register_cb (#1045).
• Removed the limit on the maximum number of parameters that can be passed to a VHDL subprogram (#1036).
• The new --no-save analysis option parses and checks the input files but does not save the working library to disk. This is a replacement for the --syntax top-level command which is now deprecated.
• The coverage database file name has changed to <toplevel>.ncdb in the current working directory and this can now be customised with the new --cover-file= elaboration option. Attempts to access the old file name inside the library directory will be redirected to the new location, with a warning.
• Partial association of ports with interface views now works correctly (#1074).
• Added support for PSL suffix implication, SERE repetition, and SERE fusion.
• Nested arrays more than two levels deep can now be dumped in FST format (#1071).
• Added support for package external names (#1072).
• Fixed parser hang for bit string literals (from @NikLeberg).
• Fixed a crash on an illegal package definition inside an interface.
• Comping the Vivado vendor libraries with nvc --install vivado is now around 2x faster and analysing files with many dependencies is up to an order of magnitude faster (#1098).
• The --jit elaboration mode now works on Windows-on-Arm systems.
• vhpi_assert now behaves the same as VHDL assert for the purposes of determining the simulation exit code and early termination (#1060).
• The 'driving_value attribute now works correctly with record types.
• Added basic support for 'instance_name, 'path_name and 'simple_name attributes of generate block labels (from @NikLeberg) (#1125).
• Comments are now parsed correctly inside PSL directives (#1129).
• Updated to OSVVM 2024.11 and UVVM 2024.10.08 for nvc --install.
• Several other minor bugs were resolved (#1038, #1057, #1067, #1124).

Version 1.14.2 - 2024-11-23

• Fixed a crash when 'last_value is used with record types (#1043).
• Fixed a crash when a process sensitivity list contains an external name and the process is elaborated before the object referenced by the name (#1062).
• Fixed parser hang for integers in scientific notation (from @NikLeberg).
• Fixed a platform detection issue that caused JIT code loading to fail on Apple silicon macOS (#1069).
• The STD_INPUT and STD_OUTPUT files can now be opened and closed multiple times (#1079).
• Fixed a crash when a subtype is used for an aggregate element association range choice which associates an array slice (#1080).
• Several other minor bugs were resolved (#1038, #1055).

Version 1.14.1 - 2024-10-26

• Fixed an error when using the work library alias and the working library has the same name as design unit being analysed (#991).
• Added a check for illegal references to signal or variable external names inside pure functions (#1010).
• Added a check that the parameter of 'stable and other implicit signal attributes is a static expression (#1018).
• Fixed an elaboration crash when an external name is passed to a procedure (#1029).
• Record subtype constraints can now be accessed over VHPI (#1035).
• Several other minor bugs were resolved (#1017, #1020, #1030, #1040).

Version 1.14.0 - 2024-09-22

• Waiting on implicit 'stable and 'quiet signals now works correctly.
• Updated to OSVVM 2024.07 and UVVM 2024.07.03b for nvc --install.
• Added a warning when an inner declaration hides an outer declaration in a way that is likely to be unintentional (#905).
• The -c sub-command for coverage is deprecated and replaced with separate --cover-report and --cover-merge commands. See the manual for details.
• The argument to the --cover-export command is now the path to a coverage database file instead of a top-level unit name.
• The --force-init command which was deprecated in the 1.7 release has been removed.
• Coverage exclude files now support fold command to merge coverage data from independent sub-hierarchies (from @Blebowski).
• FSM state coverage bin renamed from STATE to BIN_STATE.
• A signature is now allowed in the formal part of generic map associations in VHDL-2019 mode.
• use lib.pack.all no longer makes the bare package name pack potentially visible.
• Very limited initial Verilog support has been added, including the ability to instantiate vendor-supplied UDPs from VHDL.
• Fixed a regression which caused parse errors for some concurrent assertion statements (#956).
• Arrays-of-arrays with downto direction are now dumped in the correct order (#957).
• Fixed incorrect result of 'event and 'active where the prefix is an array of records.
• Fixed a crash when the 'stable attribute is used with a record type (#960).
• Conversion functions applied to individual record elements in a port map now work correctly (#963).
• External name elaboration order checks were overly strict (#964).
• Associating a signal with an out or inout parameter in a procedure that is not within a process now produces an analysis error rather than crashing at runtime (#965).
• The --dump-arrays option now takes an optional argument to specify an upper limit on the length of nested arrays to dump (#959).
• Matching case? statements are now checked for duplicate and missing choices at analysis time (#966).
• Limited maximum instantiation depth to prevent crashes due to stack overflow when elaborating a design that has unbounded recursive entity instantiation (#969).
• Physical subtype ranges and 64-bit integer types are now handled correctly by VHPI (#978).
• Added support for generic map on subprogram call in VHDL-2019 and improved support for array type generics.
• Optimised emission of FST initial signal values which also fixes a potential crash (#979).
• Added checks for duplicate attribute specification (#977).
• Several other minor bugs were resolved (#961, #962, #971, #975, #985).

Version 1.13.3 - 2024-08-24

• Type checking was not performed correctly for conversion function actuals in port maps (#945).
• Fixed a crash with signal aliases inside an instantiated generic package (#946).
• Fixed random crashes when the simulation heap size is eight gigabytes or larger (#949).
• Fixed a crash when a constant array with unconstrained element type is initialised with an aggregate (#954).
• External names in concurrent assertion statements and PSL assertions are now parsed correctly (#952).
• Several other minor bugs were resolved (#942, #943, #950, #951, #953).

Version 1.13.2 - 2024-08-11

• Fixed an incorrect bounds check error when a constant declaration has a partially constrained type (#932).
• Elaboration of large designs on Windows no longer fail with linker errors due to excessive command line length.
• Fixed a bug which prevented VCD files from being generated on Windows systems using the UCRT runtime library (#637).
• Fixed a crash when the type of a qualified expression is an unconstrained array-of-array (#934).
• Fixed random segmentation fault when the simulation heap size is larger than four gigabytes (#935).
• Fixed an incorrect ambiguous subprogram error when using the 1993 standard and calling a subprogram via a selected name such as ieee.numeric_std."=".

Version 1.13.1 - 2024-07-25

• Windows installer was missing some standard library files.
• Fixed a regression where generics and ports could not be referenced in external names (#921).
• Fixed a crash when an unconstrained port with a default value is associated with open.
• Fixed a duplicate symbol linker error with some uses of the 'delayed attribute.
• Fixed a crash when an aliased subprogram is matched by a generic subprogram <> (#924)
• Fixed a crash when a generic package containing a subprogram is passed to an entity package generic (#925).
• Fixed an intermittent "failed to suspend thread" fatal error on macOS (#922).
• Fixed a crash when a shared variable is declared inside an instantiated generic package in 2019 mode (#923).
• Fixed a crash when a port with unconstrained array-of-record type is associated with a signal that has a static subtype.
• Fixed incorrect longest static prefix calculation for array slices containing 'length, 'left, 'right and similar attributes (#930).
• Fixed wrong result when slicing a generic that has an unconstrained array type (#931).

Version 1.13.0 - 2024-07-13

• Type and package generics now work correctly with components and configurations (#883).
• Fixed a crash when a matching case? alternative contains multiple choices (#890).
• Implemented VHPI support for package declarations and vhpiPackInsts iterators (#891).
• Signatures in attribute names are now parsed correctly (#892).
• Attribute specifications for all are now parsed correctly (#889).
• Predefined "=" and "/=" operators are no longer declared for file types.
• Alias of packages now work correctly (#893).
• Stricter checking of identifiers to reject those with multiple consecutive underscores or trailing underscores (from @typingArtist).
• Stricter checking for subprograms, deferred constants, and protected types referenced before their corresponding body or full declaration.
• Decimal physical literals like 8.2 ms are now correctly rounded (to 8200 us in this case) when they are converted to the base unit (#899).
• External names can now be passed as signal actuals to subprograms (#900).
• Fixed a crash when branch coverage is enabled and an if-statement contains a return (#903).
• The NVC_CONCURRENT_JOBS environment variable can be used to scale the number of worker threads NVC creates based on the number of concurrently executing simulations.
• Fixed a crash when certain attributes such as 'val are used in the target of a signal assignment statement (#908).
• Signals in packages are now dumped to the FST file (#901).
• Function interface declarations can now be pure or impure (#917).

Version 1.12.2 - 2024-05-15

• Fixed a crash when 'transaction is used with a record type.
• Fixed a compatibility issue with LLVM 18 that could cause an illegal instruction exception when the --jit elaboration option is used (#887).

Version 1.12.1 - 2024-05-09

• Fixed a crash when a process contains a force or release assignment inside a process (all) statement (#877).
• Fixed a crash creating a waveform dump with --dump-arrays and the design contains an array-of-array-of-records (#878).
• Fixed a spurious error when a type declaration from a package generic is used in a port list (#881).
• Fixed an assertion failure when a procedure declared within a process (all) assigns to a signal (#882).
• Added a missing check for illegal assignment to external signal name outside a process (#884).
• Fixed a crash while printing diagnostic information when the simulation delta cycle limit is reached (#885).
• Generic actuals no longer need to be globally static, which was never required by the LRM (#886).

Version 1.12.0 - 2024-04-07

• The --jit elaboration option no longer requires --no-save.
• Fixed a crash when subtype bounds depend on a package instance generic (#815).
• Fixed various issues in the implementation of guarded blocks and disconnection specifications (#829).
• The --std option now controls which VHDL standard the --install command uses to compile third-party libraries (#836).
• The prefix of an indexed or slice name now must be another name or function call, as required by the LRM (#835).
• The implementation of conversions in port maps has been reworked and fixes a number of long-standing issues (#843).
• Added support for inertial keyword in port maps (#843).
• Fixed a bug where 'last_value could give the wrong result if the signal has multiple sources.
• Updated to OSVVM 2023.09a and UVVM 2023.09.16 for nvc --install.
• The --exit-severity= option now also controls which severity level results in a non-zero exit code (#850).
• Improvements to waveform dumping for signals with record types or types with non-locally-static bounds (#851, #852).
• The parameter for attributes with dimensions such as 'length(N) may be any integer type when --relaxed is passed (#862).
• Resolved several other minor issues (#654, #854, #855, #859, #863).
• The default standard version was changed to VHDL-2008.
• The --vhpi-trace option now implies --vhpi-debug.
• The bounds of array aggregates are now calculated correctly in several corner cases (#873).
• Added supported for VHPI foreign subprograms.

Version 1.11.3 - 2024-02-04

• Fixed incorrect effective value when a signal has multiple sources due to port-collapsing optimisation (#824).
• Signals that appear in aggregate choice expressions like (S downto 0 => '0') are now included in the sensitivity list for concurrent statement equivalent processes, and in process (all) (#825).
• The direction of aggregates with range choices is now calculated correctly in VHDL-2008 mode (#826).
• Fixed a memory corruption bug when evaluating certain aggregates that contain a range association (#827).
• Resolved several other minor issues (#837, #839, #840).

Version 1.11.2 - 2024-01-04

• Fixed an incorrect length check in the equivalent process for non-static port map actuals (#817).
• Library file names for design units that contain extended identifiers such as /Foo/ are now encoded in a way that avoids illegal characters and case sensitivity issues on Windows and macOS (#816).
• Implemented vhpiIsNullP and vhpiIsDiscreteP for ranges.
• Fixed a crash when an aliased enumeration literal appears in a case choice expression (#819).
• Fixed calculation of longest static prefix with indexes and slices of a constant array (#820).
• Fixed a crash during elaboration when simplifying an if-statement that depends on a generate parameter (#821).
• Increased the limit on the number of subprogram arguments to allow compiling some Lattice IPs (from @sean-anderson-seco).

Version 1.11.1 - 2023-12-16

• Fix crash during elaboration when an if-statement branch is always taken (#812).
• VHPI plugins can now access types in instantiated packages (from @sean-anderson-seco).
• The --version output now includes the bare Git commit SHA if the program is built from a shallow clone with no tags (#813).

Version 1.11.0 - 2023-12-06

• New command --cover-export exports coverage data in the Cobertura XML format which is supported by most CI environments such as GitLab.
• Generics on internal instances can now be overridden with the -g elaboration option. For example -g uut.value=42.
• Implemented the 'reflect attribute and associated protected types from VHDL-2019.
• Added support for VHDL-2019 sequential block statements.
• Implemented the VHDL-2019 directory I/O functions in std.env.
• Added VHDL-2019 assert API (with @Blebowski).
• Implemented 'image, 'value and to_string for composite types in VHDL-2019.
• Implemented the "closely related record types" feature from VHDL-2019.
• Implemented the "composition with protected types" feature from VHDL-2019.
• The new --shuffle option runs processes in a random order which can help to identify code that depends on a particular execution order.
• Updated to OSVVM 2023.07 for nvc --install.
• Various enhancements and fixes to the VHPI implementation.
• Implemented the VHDL-2019 changes to instance_name and path_name for protected type variables.
• VHPI error messages are no longer reported as diagnostic messages on the console. The new --vhpi-debug option restores the old behaviour.
• Support for type conversions between arrays with closely related element types.
• Added support for FSM state coverage collection (from @Blebowski).
• An alias of a type now correctly creates implicit aliases for each predefined operator of that type (#776).
• Improve overload resolution where a partial named association implies the formal parameter must be an array (#793).
• Handling of implicit conversion for universal types has been reworked to better comply with the LRM.
• Fixed a crash when string literal characters have a type which is an alias to another type (#801).
• Added a warning when calling the predefined "=" and "/=" operators on arrays and the left and right hand sides have different lengths.
• Expressions like abs(x)**2.0 are now parsed correctly (#805).

Version 1.10.4 - 2023-10-16

• Fixed compatibility with LLVM 17.
• Fixed an intermittent crash when using the --jit elaboration option.
• Improved overload resolution when subprogram argument is known to have character type.
• Improved bounds checking for port map actuals.
• Fixed a crash with aggregates for record types that contain an unconstrained field (#768).
• Fix spurious "checksum 00000000" error when analysing multiple design units and one contains use work.all (#769).
• Fix crash when using the --relaxed analysis option and multiple warnings are printed (#770).

Version 1.10.3 - 2023-09-17

• Fixed memory corruption in rare circumstances with functions declared in process declarative regions (#751).
• Fixed a race condition when creating library directories that occasionally led to build failures with make -j (#746).
• Aliases of protected type methods are now allowed.
• Fixed a crash when a pragma appears outside of a design unit (#752).
• Fixed a crash analysing an alias of an alias of a subprogram (#755).
• Fixed an elaboration failure when an allocator expression has an array type with an unconstrained element (#756).
• Fixed a memory leak in the --print-deps command.
• Fixed a crash when evaluating globally static expressions during elaboration with coverage enabled (#759).
• Fixed an analysis crash where a predefined function for a type declared in a package is overridden in the package body only (#760).

Version 1.10.2 - 2023-08-20

• Fixed a crash due to an array bounds check being incorrectly optimised out (#747).
• The type of string literals and aggregates in generic map associations such as G => X"00" where G has a generic type can now be determined correctly (#750).
• Fixed a spurious "duplicate declaration" error if a use clause for an instantiated packages appears in the same declarative region that instantiated the package (#750).
• Improved checking for configuration specifications.
• Empty bit string literals are now parsed correctly.
• Fixed stack corruption when a function returns an alias of one of its array arguments.

Version 1.10.1 - 2023-07-28

• Fixed incorrect sensitivity list generation with concurrent statements such as x <= C(y) where C is a constant array.
• Fixed an incorrect optimisation which caused 'event to return the wrong value in rare circumstances.
• Decimal bit string literals more than 64 bits wide are now supported (#731).
• The format of fractional time values returned by the standard to_string function was changed to match other simulators.
• Fixed a crash when constant folding a locally static expression in a package body (#742).
• Added support for reading command line arguments in VHPI (from @Forty-Bot).
• Fixed a compilation error when using the predefined minimum/maximum functions with arrays of physical types.
• Overloaded protected procedure calls could read the wrong value of protected type variables in rare circumstances.

Version 1.10.0 - 2023-07-14

• The Zstandard compression library is now a build dependency. Install libzstd-dev or similar.
• The integer type is now 64-bit in VHDL-2019 mode.
• The VUnit VHDL libraries can now be installed with nvc --install vunit but please note this does not install the Python infrastructure.
• Updated to OSVVM 2023.05 and UVVM 2023.03.21 for nvc --install.
• Conditional expressions are now allowed in constant, signal, and variable declarations in VHDL-2019 mode.
• Conditional return statements are now supported in VHDL-2019.
• Added support for the "function knows vector size" feature in VHDL-2019.
• Entity ports with variable class and protected type are now supported in VHDL-2019 mode.
• The xpm_vhdl project which provides VHDL models of the Xilinx XPM macros can now be installed with nvc --install xpm_vhdl.
• Many improvements to the VHPI implementation (from @Forty-Bot).
• vhpi_put_value with vhpiDepositPropagate mode is now supported.
• The Synopsys std_logic_misc package is now compiled for 2008 (#696).
• Fixed an issue where leading NUL characters in a report message would prevent the entire message being printed (#700).
• Added support for interfaces in VHDL-2019 including mode view declarations, mode view indications, and the 'converse attribute.
• Added support for VHDL-2008 matching select? statements (#705).
• Added support for the new 'designated_subtype and 'index attributes in VHDL-2019.
• Implemented the date/time functions from std.env in VHDL-2019.
• The default exit severity was changed from error to failure. This means a failing assertion no longer immediately terminates the simulation. The old behaviour can be restored with --exit-severity=error.
• Comparison operators as well as minimum/maximum functions are now defined for all scalar array types in VHDL-2019.
• Added support for selected signal and variable sequential assignment statements.
• The -a analysis command now accepts an -f list option where list is a text file containing a list of files to analyse. Alternatively this may be written @list.
• Accesses to protected types and files are now allowed in VHDL-2019.
• Fixed a crash when indexing a null array (#734).
• Named and range choices are now supported in aggregate targets of variable and signal assignments (#712).
• The synopsys.attributes package is no longer distributed or built as part of the standard libraries.

Version 1.9.2 - 2023-05-01

• Fix elaboration errors with recursive entity instantiation (#668).
• Updated to latest GtkWave FST writer library.
• Fix crash when an external name is used in a wait expression (#674).
• Fix stack corruption when passing large numbers of arguments (#665).
• Protected procedure calls with out or inout signal arguments now create drivers (#675).
• Fixed a crash when a next or exit statement appears inside process (all) (#676).
• The --jit elaboration options now works on Intel Macs (#680).
• Fixed a corner case where a forced signal with no drivers had the wrong effective value after release (#681).
• Fixed a crash when a signal assignment statement contains only unaffected (#677).

Version 1.9.1 - 2023-04-15

• Fix build errors and warnings on MSYS2 Clang x64 environment.
• Fix build failure due to missing SHT_X86_64_UNWIND on Alpine and Ubuntu 18.04 (#666).
• Elaboration now works correctly when the --with-system-cc= configure argument is given a non-absolute path (#667).
• Fixed a crash when a subprogram declared in a for-generate block is called during elaboration (#668).
• Real to physical or 64-bit integer conversion now produces the correct result when evaluated during elaboration (#669).
• Matching case? statements are now handled correctly in inside process (all) (#670).
• Pass -no_fixup_chains to linker on macOS to avoid warning.
• ; can now be used as a separator in the --work and --map arguments on Windows in addition to : (#671).

Version 1.9.0 - 2023-04-07

• Code generation has been rewritten to enable faster elaboration and "just-in-time" compilation in the future.
• Now compatible with LLVM 16.
• Implemented the VHDL-2019 call path reporting API.
• The elsif VHDL-2019 conditional analysis directive now works correctly (#604).
• The 'transaction implicit signal no longer incurs a delta-cycle delay.
• x'ascending now reports the correct result if x has unconstrained array type and null range.
• The predefined "=" operator on record types now always uses the predefined equality comparison for fields even in the presence of a user-defined "=" operator.
• It is no longer necessary on Windows to link VHPI plugins at elaboration time with NVC_FOREIGN_OBJ. Use the --load option to load the plugin at run time as on other operating systems.
• The experimental --jit elaboration option defers native code generation until run time. This can dramatically reduce total test time for short-running simulations.
• Statements like wait for X where X is negative but not a constant now produce an error at run time (#633).
• NVC is now supported by VUnit.
• Implicit signal attributes like 'transaction are now considered static signal names (#640).
• Added support for fine-grained coverage collection via --coverage-spec elaboration option (from @Blebowski).
• The ABI for passing unconstrained arrays to foreign subprograms changed slightly, see the manual for details.
• Implemented new file I/O operations from VHDL-2019.
• Added analysis option --define to set user-defined conditional analysis identifiers (from @Blebowski).
• Optional support for using ZSTD to compress library files if libzstd-dev is installed.
• ISO-8859-1 extended characters are now handled properly in identifiers and when printing to the terminal.
• The new configure option --disable-default-paths disables the default library search paths (#652).
• Subtype indications used as case range choices no longer crash during analysis (#655).
• The default standard version was changed to VHDL-2002 and will likely change again to -2008 in a future release. Users are recommended to use the --std= option to specify an explicit standard revision to avoid any compatibility issues.
• Fixed a crash when elaborating a port map which contains a subtype of a record (#662).
• Implemented VHDL-2019 syntax relaxations for empty records and trailing semicolon in interface lists (from @bpadalino).
• A Bash auto-completion script is now installed by default. Run configure with --without-bash-completion to disable this.

Version 1.8.2 - 2023-02-14

• Fixed "failed to suspend thread" crash on macOS.
• Fix incorrect coverage scope nesting with array case statements (from @Blebowski).
• Expressions like FOO(X)'DELAYED now work as expected rather than producing a fatal error (#603).
• Fixed a bug where data was not propagated through inout ports in certain conditions (#609).
• The -gNAME=VALUE option to set generic values from the command line now works correctly for subtypes of enumeration types (#618).
• Fixed crash when creating an array of record subtypes where the subtype declaration has an element constraint (#615).

Version 1.8.1 - 2023-01-23

• Initial signal values for certain types were not dumped correctly in FST files on Windows (#596).
• Missing thirdparty/str-two-way.h from distribution tarball (#599).

Version 1.8.0 - 2023-01-22

• The --disable-opt and --native elaborate options which were deprecated in version 1.3 have been removed.
• The JSON dumper which was unmaintained for several years has been removed.
• VHDL-2019 mode can be enabled with --std=2019. Please note there is very limited support for this standard at present.
• The new --no-save elaboration option skips saving the elaborated design and other generated files to the working library.
• Added support for else and elsif in generate statements (#510).
• Xilinx Vivado vendor libraries can now be compiled with nvc --install vivado.
• LLVM 8.0 or later is now required due to deprecation of non-opaque pointers.
• Altera/Intel Quartus vendor libraries can now be compiled with nvc --install quartus.
• The nvc --version output now includes the commit hash if built from a Git checkout.
• The new --gtkw run option writes a .gtkw save file for GtkWave containing all the signals in the design (suggested by @amb5l).
• libffi is now a build-time dependency.
• Negation of the smallest negative value of a type such as -integer'left now produces an error.
• Default OSVVM version updated to 2022.11.
• case .. generate statements are now supported in VHDL-2008.
• Coverage implementation was reworked and now collects statement, branch, expression and toggle metrics (from @Blebowski).
• The --make command is deprecated and will be repurposed in a later release. Use the new --print-deps command instead to generate Makefile dependencies.

Version 1.7.2 - 2022-10-16

• Fixed build on FreeBSD/arm (#534).
• Fixed crash with generic package instantiation (#520).
• Now compatible with LLVM 15.0.
• Fixed calculation of longest static prefix with 'RANGE expression (#542).
• MOD and REM are now defined for physical types in VHDL-2008 (#540).
• Signal declarations are now allowed in entity declarative part (#547).
• Protected objects are now allowed in concurrent procedure calls (#547).
• Opening a file with APPEND_MODE now actually appends to the file instead of truncating (#551).

Version 1.7.1 - 2022-08-31

• Added missing textio WRITE [LINE, REAL, STRING] in VHDL-2008.
• Added support for FreeBSD/powerpc (#503, #504, from @pkubaj).
• Fixed "missing vcode unit" error during elaboration (#502).
• Fixed crash with recursive entity instantiation (#502).
• Fixed error with expressions like X'ELEMENT'LENGTH (#508).
• Added support for FreeBSD/i386.
• Fixed crash reading resolved value of record signal (#502).
• Improved folding of for-generate expressions (#514).
• Fixed memory leak when forcing signals.
• Fixed crash with type conversion in generic map (#518).
• Fixed crash with expressions like X'DELAYED'STABLE (#517).
• External names now work with record signals (#520).
• Xilinx Vivado vendor libraries can now be compiled with nvc --install vivado.
• VITAL libraries are now built by default on Windows.
• Fixed build with old versions of Glibc.
• Resolution functions with nested record types now behave correctly (#516).
• Avoid repeated stat(2) calls when accessing library.
• Fixed very slow elaboration in some cases with function calls in generic map expressions.
• Fixed intermittent segfault during elaboration (#506).
• Fixed incorrect constant folding of case statements with range choices.
• Fixed crash with constrained array declared in entity.
• Real valued signals can now be dumped in FST files (#524).
• Fixed signal assignment delay with side effects being evaluated twice (#527).
• An error is now reported for duplicate choices in array-type case statements (#528).

Version 1.7.0 - 2022-08-07

• Breaking change: In-tree builds are no longer supported: use a separate build directory instead.
• Breaking change: The --force-init command is deprecated and has no effect.
• Added support for VHDL-2008 type generics on packages and entities.
• Diagnostic messages have been enhanced with more contextual information.
• Added support for record element constraints and record fields with unconstrained array types.
• Alias of multidimensional array allowed in VHDL-2008 mode.
• Implemented VHDL-2008 rules for aggregates with slices.
• VHPI is now always enabled at build time and the --enable-vhpi configure option has no effect.
• Arithmetic operations that overflow the underlying machine type now produce an error (#101).
• Added support for VHDL-2008 force/release assignments.
• Basic support for external names in VHDL-2008.
• Matching case case? statements are supported in VHDL-2008 mode.
• Fixed several bugs in the implementation of guarded signals.
• Implemented VHDL-2008 rules for generic visibility.
• Shared variable declaration permitted in entity declaration.
• Case expression no longer requires a locally static subtype in VHDL-2008 mode (#460).
• The VHDL heap is now garbage collected as required by VHDL-2019 and the deallocate operator has no effect other than setting the access to null.
• A new global option -H specifies the size of the simulation heap and defaults to 16 megabytes.
• Concurrent procedure call allowed in entity statement part.
• Added support for 'SUBTYPE and 'ELEMENT attributes in VHDL-2008.
• The new top-level --init command creates a new empty library directory.
• The -a analysis command now reads from the standard input if the file name is -.
• Added support for array element constraints in VHDL-2008.
• The --prefer-explicit analysis option which was deprecated before the 1.0 release has been removed.
• A new --relaxed analysis option enables "relaxed rules" mode. This has the same effect as enabling all the existing --relax= options. However some constructs will still produce warnings.
• The --relax= analysis option is deprecated and is now equivalent to passing --relaxed. The individual options are ignored.
• Added support for generic subprograms in VHDL-2008.
• New command --install allows easy installation of common third-party packages such as OSVVM and UVVM.
• Identifiers in waveform dumps are now in lower case instead of upper case.
• The function CURRENT_DELTA_CYCLE in NVC.SIM_PKG can be used to query the current delta cycle number.

Version 1.6.2 - 2022-04-03

• Fix make -j with GNU make (#440).
• Subtraction from zero could return the wrong result in some circumstances.
• Fix incorrect code generation for access-to-array.
• Fix assertion failure with nested context.
• Generic declarations are now allowed to hide the entity name.
• Fix spurious error about duplicate declarations when using VHDL-2008 context declarations.
• Fix incorrect default generic value when component and entity specify generics in different order (#448).
• Postponed processes with sensitivity lists now work correctly.
• Unit tests no longer fail when built without debug symbols (#445).
• Simulation now correctly terminates when time reaches TIME'HIGH.
• Assertion failure and report messages were not printed during the initialisation phase of the simulation.

Version 1.6.1 - 2022-02-05

• Fix compatibility with BSD make (#440).
• Fix an out-of-memory condition when initialising processes (#441).
• Fix incorrect generic value in binding specification (#442).
• Fix spurious error in overload resolution if required arguments follow optional arguments (#443).
• Fix intermittent crash generating code for enumerated types (#444).
• Minor elaboration performance optimisation.

Version 1.6.0 - 2022-01-25

• Name resolution and overload resolution has been completely rewritten which should fix a number of long-standing issues.
• The elaboration phase was largely written which fixes a number of long-standing issues and significantly improves elaboration speed.
• VHDL-2008 IEEE standard libraries are now built and installed in addition to the VHDL-1993 libraries.
• The VHDL-1993 standard libraries are now derived from the Apache 2.0 licensed sources from VHDL-2019.
• There is now a project website at https://www.nickg.me.uk/nvc/. Please link to this in preference to the GitHub project page.
• Compiled VHDL code now includes DWARF debug information which is used for runtime stack trace if libdw or libdwarf is installed.
• Added support for VHDL-2008 reduction operators, match operators, and condition conversion.
• Added support for VHDL-2008 element resolution.
• Variable assignment now supports aggregate targets.
• The --relax=impure option allows pure functions to call impure functions.
• Added support for VHDL-2008 "all" sensitised processes.
• Added support for ports and generics in block statements.
• Added support for the 'BASE attribute.
• Type name now allowed in element association choice (#407).
• Implement textio READ procedure for REAL.
• LLVM 6.0 or later is now required to build.
• Added support for MINIMUM, MAXIMUM, and TO_STRING predefined operators in VHDL-2008.
• VCD files are now generated from FST data in a similar manner to fst2vcd(1). This should improve compatibility with other tools.
• Added support for 'LAST_ACTIVE attribute (#423).
• Added support for 'DRIVING and 'DRIVING_VALUE attributes.
• Added a new option --ieee-warnings=off to disable warning messages from the standard IEEE packages.
• Support for configurations has been significantly improved (#372).
• Added support for VHDL-2008 delimited comments.
• Added support for guard expressions on blocks.
• Added support for guarded signals.
• Added support for HREAD, HWRITE, and other TEXTIO additions in VHDL-2008.
• Code generation now happens in parallel when LLVM is built with multi-threading enabled.
• Link time optimisation (LTO) is now enabled for release builds where supported.
• The default assertion failure message for certain simple scalar comparisons now shows the values of the left and right hand sides.
• Added support for VHDL-2008 conditional variable assignment statements.
• Added support for VHDL-2008 extended bit string literals.
• Non-globally-static actuals allowed in port maps in VHDL-2008 mode.
• Added support for VHDL-2008 sequential conditional signal assignment statements.
• Added basic support for package generics and package instantiation.
• Nested arrays can now be included in the waveform dump but only if the --dump-arrays option is passed. This is disabled my default due the significant performance and memory overhead.
• Added support for record types in waveform dump (#216).
• Added support for foreign subprograms using the VHPIDIRECT protocol.
• Library build is now reproducible when running make -j.
• Fix a constant folding crash with nested records.
• Fixed a crash when a record aggregate contains an "others" association and the fields have array types with different lengths.
• Fixed a stack overflow when a subprogram with unconstrained array arguments is called repeatedly in a loop (#414).
• Fixed intermittent crash when evaluating nested constant records (#425).
• Fixed missing import libraries on Windows (#424).
• Standard libraries are now installed under $prefix/lib/nvc/ instead of $prefix/share/nvc.
• New configure option --disable-vital disables building the VITAL packages whose license status is unclear.
• Support for the LXT wave output format, which was deprecated in version 1.5, has been removed. Use the default FST format instead.
• The fetch-ieee.sh script which did nothing since the last release has been removed.
• The --codegen command, which has been deprecated since 1.3, was removed.
• The --profile option now prints internal simulation statistics instead of the top processes by CPU time.

Version 1.5.3 - 2021-11-13

• Handle access(2) returning EPERM in macOS sandbox (#421).
• Fix race when multiple processes concurrently update a library.
• Fix --syntax command when file contains multiple design units.
• Allow constant folding of nand/nor/xor/xnor.
• Fix potential out of memory condition when evaluating complex assert expressions.
• Fix incorrect result of mod operator with negative operands.
• Fixed intermittent crash when evaluating nested constant records (#425).
• Buffer too small for printing TIME'HIGH (#98).

Version 1.5.2 - 2021-07-28

• Link libexecinfo on FreeBSD.
• Implement textio READ procedure for BIT and TIME (#408).
• Fixed a crash when a long running procedure suspends in a loop (#412).
• Fix static linking with LLVM 12.0.
• Fix crash when assigning to a signal declared in a package.
• Fix incorrect recording of dependencies which caused a failure to load generated DLLs on Windows.
• Fix file locking error when a library is located on NFS (#417).
• Optimise loading large library index from disk.
• Fix a crash when using 'VALUE with enumeration subtypes (#419).
• Fix a crash when a signal with more than 256 elements is declared in a package (#420).

Version 1.5.1 - 2021-04-09

• Fix a compiler warning in vcode.c.
• Disable VHDL backtrace on non-Linux systems as the symbol names cannot be parsed reliably (#385).
• Update to latest pc_from_uncontext.m4 for Apple M1 support.
• Fix incorrect application of LRM rules for building an equivalent wait statement for concurrent statements.
• Library build is now reproducible when running make -j (#409).
• Fix assertion failure with nested record type (#404).
• Use Pandoc to generate the manual page.

Version 1.5 - 2020-07-19

• IEEE library sources are now distributed
• Updated FST library to match GtkWave 3.3.79
• The LXT wave output format is deprecated, use FST instead
• Fix incorrect file name in assertion message
• Fix crash while recovering from parse error
• Add --dump-json command to print AST as JSON (from Sebastien Van Cauwenberghe)
• Fix crash when using LLVM 7 and later
• Fix spurious assertion failure in std.textio.readline
• Reals are now rounded to the nearest integer as specified by the LRM
• Fix crash when constant folding uses too much memory
• Improved memory management in evaluator (thanks to Frank Mori Hess)
• Various other minor fixes and improvements

Version 1.4 - 2018-07-16

• Windows with MSYS2 is now fully supported
• Continuous integration for OS X and Windows using Travis and AppVeyor
• Record resolution functions are now supported
• The --relax=prefer-explicit option now works correctly

Version 1.3 - 2017-12-31

• Native code is always generated on platforms that support it
• Initial support for VHDL-2017 conditional compilation blocks
• The TCL shell has been removed
• Various code generation and constant folding fixes
• Fix crash when build IEEE library from non-clean tree
• ORC is used for JIT if LLVM version is 3.9 or later
• LLVM 3.8 or later is now required
• Added -O0 to -O3 options to control LLVM optimisation level
• The --disable-opt option is deprecated, use -O0 instead
• The elaborate --native option is now a global option and should be placed before the -e command
• The --codegen command is deprecated, use --native when analysing to generate native shared libraries for packages

Version 1.2 - 2017-05-04

• Compile time evaluation now uses vcode
• Record aggregates can now be constant folded (#305)
• The TCL shell is deprecated and will be removed in the next release
• Compatible with LLVM 4.0
• Functions returning records can now be constant folded (#315)
• LLVM 3.4 or later is now required

Version 1.1 - 2016-11-05

• Improvements to based literal parsing
• Improved stack traces on Linux when libdw-dev installed
• Fixed elaboration of subprograms in entity declarations
• Improved elaboration performance when design contains many signals
• Fixed various bugs involving record signals
• Fixed sensitivity list generation for concurrent procedure calls
• Improvements to simulation performance
• Implemented vhpi_get_phys
• Added command --list to print all units in a library
• Rewrote the run_regr program in C so make check no longer requires Ruby
• The --relax=generic-static option is now renamed to --relax=locally-static and applies in wider range of contexts

Version 1.0 - 2016-05-01

• First stable release