free and open-source analyzer, compiler, simulator and (experimental) synthesizer for VHDL

[Next] 4.0#

GitHub v4.0 milestone

[2023-03-08] 3.0#

GitHub v3.0 milestone

  • Handle IEEE operators for static expressions.

  • Improved support of VHDL 2008 (still!).

  • Start support of VHDL 2019 (--std=19).

  • pyGHDL:

    • Experimental support to preserve VHDL code comments for documentation extraction.

    • Experimental packaging with a platform-specific shared library for standalone installation using PIP.

    • DOM: dependency graphs, instantiation graphs (design hierarchy), file dependencies (compile order).

  • Pre-releases are published to GitHub Releases and assets are uploaded to pre-releases and releases.

[2023-03-06] 3.0.0-rc.4#

See 3.0.

[2022-02-28] 2.0#

GitHub v2.0 milestone

  • Improvements to VHDL 2008 supports and synthesis.

[2021-02-02] 1.0#

GitHub v1.0 milestone

  • Python bindings overhauled and renamed to pyGHDL. Three modules are included: libghdl, lsp and dom.

  • Utility scripts in the codebase moved into subdir scripts: CI, binding generation, vendors, etc.

  • Repository ghdl/ghdl-cosim created. It contains documentation and code examples related to VHPIDIRECT, VPI and SystemC.

  • GitHub Action ghdl/setup-ghdl-ci created, to allow easy installation of nightly GHDL assets in GitHub Actions workflows.

  • Main documentation site(s) moved to and

  • Repository ghdl/extended-tests created for testing vendors build scripts.

  • Logo updated (org, ghdl/ghdl, ghdl/docker and ghdl/ghdl-cosim).

  • Assets not added to releases or pre-releases anymore. Users should use package managers or nightly assets (updated after each successful CI run of branch master): nightly.

[2021-01-31] 1.0.0rc1#

See 1.0.

[2020-05-21] Nightly build assets#

  • After each successful CI run of branch master, packages are published as assets of pre-release nightly.

  • GitHub Action ghdl/setup-ghdl-ci was created, to allow easy installation of nightly GHDL assets in GitHub Actions workflows.

[2020-05-09] New repositories and a wiki#

[2020-02-28] 0.37#

GitHub v0.37 milestone

  • Python binding added

  • Experimental support of synthesis (either with –synth or with the Yosys plugin)

  • Fixes and improved support of VHDL 2008

    • PSL keywords are directly handled in VHDL 2008

  • Add support for assume.

  • Last version that supports the Mentor variation of std_logic_arith. The Synopsys one is still available.

[2019-03-03] 0.36#

GitHub v0.36 milestone

  • More support of unbounded arrays and records.

  • Support of UVVM and VUnit.

[2019-02-23] 0.36-rc1#

See 0.36.

[2018-11-29] 20181129#

[2017-12-20] GitHub organization#

A new GitHub organization is created and the main repo is moved from to Old refs will continue working, because permanent redirects are set up. However, we suggest every contributor to update the remote URLs in their local clones.

[2017-12-14] 0.35#

GitHub v0.35 milestone

  • Assert and report messages are sent to stdout (#394)

  • Improve support for unbounded records

  • Bugs fixed

[2017-08-15] 0.34#

GitHub v0.34 milestone

  • Display stack backtraces on errors or assert failures

  • Compile scripts for vendor libraries (Xilinx, Altera, osvvm, vunit)

  • Use SSE2 for mcode backend

  • mcode backend ported to x86_64

  • Support cocotb potentialventures/cocotb

  • Main repository is now on github:

  • Docs available on rtd:

  • Speed improved.

  • New option --psl-report, to report status of PSL assert and cover.

  • VHDL2008: support nested package

[2015-10-23] 0.33#

[2014-11-XX] 0.32#

  • Updated to build with gcc-4.9.2.

  • support: - partial of VHDL2008 (available with --std=08): - new std.env package. - added features in std.textio package - all standard IEEE packages. - new operations (relation operators, maximum and minimum, unary reduction operators) - boolean_vector, integer_vector, real_vector. - process(all). - generic packages and interface package declarations. - block comments (aka delimited comments) - implicitely defined to_string functions. - OSVVM 2014_01

  • Bugs fixed

[2014-01-XX] 0.31#

  • Updated to build with gcc-4.8.2.

  • Supports OSVVM (Open-Source VHDL Verification Methodology) (see in its VHDL-2002 form.

  • Adds 'image and 'value attributes for all required datatypes

  • Many bugs and support issues fixed.

  • New home on


Never released, swith to Dunoon Edition.

[2010-01-09] 0.29#

  • Initial implementation of embedded PSL assertions.

  • Improve: - speed of non-sensitized processes. - speed of string case statement (dichotomy instead of linear search).

  • bug fix: - and improvements in SDF annotator. - when the bound of a string literal type is not locally static. - gcov crash

[2009-09-17] 0.28#

  • Add --std=08 to enable VHDL2008 features.

  • Support all-sensitized processes from VHDL2008.

  • Documentation typos (thanks to Peter Huewe).

  • bug fix:

    • handle 'pos/'leftof/'rightof/'succ/'pred in concurrent statements.

    • overloaded resolution functions.

    • direct drivers elaboration for unconstrained array signals.

    • many minor bugs.

[2008-07-01] 0.27#

  • Improve SDF annotation (handles much more annotations)

  • Add --ieee-asserts= option to control assert messages from ieee packages.

  • bug fix:

    • aliases in port map

    • crash during elaboration for top entities with ports/generic

    • crash when string literal in aggregate.

    • concatenation with an array subtype element.

    • non-static subtype used by type conversions in associations.

    • clear timeout in wait for.

    • minor bugs.

[2007-04-08] 0.26#

  • GHDL_PREFIX environment variable overrides default installation prefix.

  • simulation speed improved with ‘direct drivers’.

  • windows version: - exceptions are caught - use executable path instead of registry for prefix

  • bug fix: - individual association by expression (was not working) - individual association of string - within windows code generator - [windows] large local variables crashed - crash when overloaded aggregate target. - forbid individual association with open - crash when bad array prefix - correctly extract sensitivity of record aggregate

[2006-08-11] 0.25#

  • VPI functions to schedules values.

  • math_real now works under windows.

  • documentation updated for windows.

  • filename/line number displayed for range error during signal update.

  • bug fix: - ieee math libraries available when --ieee=synopsys. - 'image in package bodies. - scan of fp literals. - interface identifier is checked for conformance rules. - avoid a crash in case of error in configuration specification. - non-static choice in unidim case are now correctly checked. - do not crash in case of bad use of incomplete type. - 'range are not expressions. - handle file declaration in concurrent procedure calls. - correctly handle static 'image attribute. - handle in-conversion for signal associated with an expression. - emit an error when a function tries to exit without a return.

[2006-06-25] 0.24#

  • Handle enums with more than 256 elements.

  • Relax expr static rules in 93c to analyze Xilinx core lib from 8.1

  • man page, ghdl.1, added.

  • windows installer improved

  • bug fix: - correctly handle empty file name. - correctly handle unused subprograms of protected types. - avoid a crash if unused library are used. - avoid crashes during error reports. - add a missing case array conversion. - build on x86_64. - code generated for conversion after mod/rem (windows version). - -fexplicit crashed with std.standard functions. - handle recursion of pure/wait checks. - correctly handle error cases of user attributes - time and character read procedure of std.textio. - initialize by value parameters (instead of copy-in).

[2006-05-16] 0.23#

  • bug fix: - handle implicit conversion in resolution functions. - missing implicit conversion added. - avoid a crash in error.

[2006-03-28] 0.22#

  • direntry added in ghdl.texi

  • updated: - Documentation (explain bug in Xilinx unisim library). - to gcc 4.1 - math_real

  • bug fix: - avoid crash if type conversion is indexed/sliced - do not allow anymore uncomplete individual association - missing check on array association - check bounds for val attribute on enumerated type - array inequality of locally static expressions evaluated - configuration issue - --warn-no-vital-generic is now working

[2005-12-18] 0.21#

  • local optimizations (loops, indexed name).

  • simulation speed improved by 20% due to processes mngt optimizations.

  • stack-switching code ported to x86_64 (amd64/em64t).

  • stack-switching code ported to ia64.

  • --syn-binding option extended (see documentation).

  • bug fix: - line number for some bound violation messages. - improved message error for deferred constants. - file parameter for functions. - universal real divided by integer handled in locally static expr. - std_ulogic types and arrays are known by VPI. - missing space added in VCDs for integers. - CR+LF is also end of line for std.textio.readline. - avoid a crash if parse error on choice. - handle 'image in nested subprograms. - handle 'image for floating point types. - do not use varargs C calls. - handle missing EOL for readline. - for x86_64

0.20 [2005-10-15]#

  • stack memory usage improved for shortcurt operations.

  • gtkwave now displays nice waves for bit and std_ulogic signals.

  • time unit is displayed in assert/report message.

  • -fexplicit option added.

  • integers are now written in VCD files.

  • hash table added for design_units (speed optimization).

  • range checks slightly optimized.

  • --vcdz run time option added.

  • improved error message for invalid expressions.

  • grt now compiles with GNAT-GPL-2005 (use a GNAT bug work-around).

  • bug fix: - handle more types for --dump-rti and --wave. - 'last_event and 'last_active (bad value returned when no previous event or activity). - 'image attribute for physical types (was bad unit). - 'image attribute for locally static integers. - for reading .ghw files. - in --xref.

[2005-08-17] 0.19#

  • ADAFLAGS has been replaced by GHDL_ADAFLAGS to ease compilation.

  • ieee.math_real and ieee.math_complex added (only partially, based on a draft).

  • current time is printed with assert/report messages.

  • stack switch assembly code ported to powerpc-linux.

  • documentation on how to use grt from Ada added.

  • allow indexes of indexed names to be non-static in case statements (93c only) (this is not standard, but I can’t see why it should be required).

  • unbound ports of entities are now reported with --warn-binding.

  • some error or warning messages improved.

  • --wave option added to dump waveforms (using ghw file format).

  • bug fix: - internal error (missing close_temp for implicit read) - --xref-html: avoid to reanalyze unit. - handle implicit conversion for 'image. - aggregate assigned to an aggregate: avoid crash. - array attributes on unconstrained array: avoid crash. - 'last_event returns time'high if no event. - 'last_event on array (uninitialized variable). - allow calling rising_edge with a port of mode buffer. - allow aliases of unconstrained arrays. - bound error on aggregate with an unused other association. - catch indexed/sliced component (was crashing). - catch index/slice of a type conversion (was crashing). - handle bad component specification in conf (was crashing). - missing ports in component (was crashing). - component configurations were dicarded by bug in some cases. - no more unused warnings for subprograms in architectures (they may be used in configuration). - allow conversion in component configuration. - conversion in associations with not statically defined array signals.

[2005-03-12] 0.18#

  • Keep last line number to speed-up line number look-up (improvement).

  • --warn-default-binding added, --warn-binding rewritten.

  • 'value implemented for integer numbers.

  • bug fix: - in for time. - file_close does not crash if file was already closed. - spurious unused warnings for protected types. - allow subtype names in slice during sensitivity extraction. - correctly set the default value of collapsed ports. - handling of stack2 (aka large concatenation bug).

[2005-02-26] 0.17#

  • command --elab-run added.

  • Code generation for aggregate improved.

  • Library name of option --work= is checked.

  • --no-run option added to prevent simulation (may be used to disp tree only).

  • disp signal name in error when multiple sources drive an unresolved signal.

  • -m/--gen-makefile now handle several libraries.

  • dependences are not stored anymore in libraries (shorter/faster).

  • mentor version of ieee library is now provided.

  • handling of universal types is more consistent with LRM (almost corner cases).

  • iterator and indexes whose bounds were universal expressions are now of type integer or erroneous, according to the weird LRM rules.

  • handle selected name as entity name in architecture/configuration.

  • bug fix: - port map with expression (corner case ?). - forbid empty extended identifiers. - enumeration literal xrefs. - non-object name in sensitivity list crashed. - correctly handle alias of signals in processes.

[2005-01-02] 0.16#

  • std.textio: readline has no limits on line length.

  • command -r (run) added.

  • bug fix: - better handling of errors in type conversion. - few uninitialized variables in ghdl itself caught. - parse error: begin in aggregates. - bad unused subprogram warnings.

[2004-10-13] 0.15#

  • library file format modified to handle relative pathes.

  • install fixed to use relative pathes.

  • internal change: ortho API modified (constant are not anymore expressions).

[2004-08-29] 0.14#

  • pretty printing in HTML command, --pp-html, added.

  • xref generation in HTML command, --xref-html, added.

  • syntax checking command, -s, added.

  • Code generation in whole command, -c files -e unit, added.

  • warns for unused subprograms.

  • bug box added to help bug reports.

  • -s (syntax check) command added.

  • Missing grt subprogram to close non-text file added.

  • maximum line length of std.textio.readline extended to 512 characters.

  • std.textio.readline assert error on truncated lines.

  • Handle P32 and P64 in --trace-signals

  • sequentials statements are not canonicalized (should be faster).

  • DESTDIR added in Makefile to ease packaging.

  • for -m command, re-parse modified files of the work library.

  • Many checks added on interfaces.

  • Many checks added on associations, better handling of conversions.

  • Checks for unassociated entity ports at elaboration.

  • bug fix: - resolution function can be an expanded name. - missing type check in a corner case. - emit an error when EOF is reached while a text file is read. - for negative number. - [integer]: correctly handle end of line. - parameters of protected type: handled and checked. - gen_tree.c modified to work with sparc.

[2004-06-26] 0.13#

  • support of 64bits integers and 32bits time (not yet user available)

  • handle 'high and 'low attributes on non-locally static types and subtypes.

  • Many warning switches added (to control output of warnings).

  • --gen-makefile mode added to ghdl (to generate a Makefile)

  • alias identifier restrictions of vhdl-02 implemented.

  • declarative region for architecture from vhdl-02 implemented.

  • buffer port association rules of vhdl-02 implemented.

  • method operator restrictions of vhdl-02 implemented.

  • 'driving and 'driving_value implemented.

  • run-time bound check error message now contains file name and line number.

  • strings are not stored anymore with the identifiers.

  • parser does not back-track anymore.

  • bug fix: - name clash in generated .s files (arch and port/generic names). - implicit conversion of signal parameters. - handle locally static type conversion of arrays. - stabilize during elaboration of an unconstrained signal. - revert previous vhdl87 conf spec bug fix, according to INT-1991 issue 27. - multiple visibility of declarations (eg: direct and alias). - names attribute of non-object aliases.

[2004-05-30] 0.12#

  • simulation speed improved (2 fold) due to reduced activity optimization.

  • type conversion handled in associations

  • make mode of ghdl improved.

  • bug fix: - attribute specification - allow discrete type marks in choices - handling of generate statement for VCD - allow dereference in variable associations - allow function conversion in block port map - vhdl87: apply configuration specification inside generate stmts. - catch non-passive concurrent procedure calls in entity. - association of an unconstrained port with an expression. - declaring an uncons. array subtype of an uncons. array subtype.

[2004-04-24] 0.11.1#

  • bug fix: - corner case of signal not updated - handle 'stable, 'quiet with a paramater > 0 - typos (missing + ) in sparc.S

[2004-04-17] 0.11#

  • signal collapsing improved.

  • simulation kernel speed improved (maybe 5x faster).

  • --lines mode of ghdldrv added.

  • boolean signals are now dumped in vcd files.

  • bug fix: - in code generation for an aggregate. - run-time check of ascending order of projected transactions. - empty sequence of stmts in case alternatives (unidim array). - evaluation of locally static ‘range attribute. - implicit conversion in formal function convertor. - return type is a type mark.

[2004-02-28] 0.10#

  • architecture with many instances can be compiled with less memory.

  • --stats option added to the simulator, to evaluate performance.

  • signals are now collapsed between instances, if possible.

  • simulation is about 3x faster.

  • sparc port available (source only).

  • more checks added for attribute specification.

  • chop command added (split files by design unit).

  • bug fix: - absolute source files. - empty sequence of statements in case alternatives.

[2004-02-01] 0.9#

  • VITAL level 0 restrictions checks added.

  • VITAL 2000 packages provided.

  • run-time information (such as signal names) rewritten.

  • SDF support added (partial and experimental).

  • bug fix: - allow elaboration even if no package body if the package is present in a file but not used by the hierarchy. - delay_length range is pre-elaborated (was not in v93). - crashed when a design unit is not found at elaboration. - allow association of 'stable, 'quiet… with signal interfaces. - concurrent procedure call creates a non-sensitized process. - effective value of non-scalar resolved signal might not be set.

[2003-11-05] 0.8#

  • protected types (from 1076a/1076-2000) implemented.

  • file declarations are finalized in subprograms.

  • an exit call-back has been added in the run-time library.

  • internal modifications (nodes are stored in a table).

  • name of generated executable can be set with -o option.

  • IVI ( support through a few VPI subprograms.

  • pure and wait checks added.

  • out ports are correctly dumped in VCD files.

  • bug fix: - signal declaration not allowed in processes. - several bugs fixed.

[2003-08-02] 0.7#

  • layout of internal nodes improved.

  • incremental binding (vhdl93).

  • association of in port with expressions (vhdl93).

  • --disp-time option added.

  • make mode (ghdl -m) rewritten.

  • 'simple_name, 'path_name and 'instance_name added (vhdl93).

  • bug fix: - instantiation added in hierarchy. - individual association of subelements by expression. - --stop-delta option is working. - correctly handle operators names at function call. - several small bugs fixed.

[2003-06-09] 0.6#

  • internal modifications (single linked list used instead of arrays).

  • Mentor version of std_logic_arith is provided.

  • postponed handled (vhdl 93).

  • declarations allowed in a generate statement (vhdl 93).

  • non object aliases handled (vhdl93).

  • signatures handled (vhdl93).

  • bug fix: - xnor on bit and boolean is working. - selected_name list in use clauses. - many other small bug fixes.

[2003-05-10] 0.5#

  • foreign attribute handled. You can now call subprograms defined in a foreign language (such as C or Ada).

  • ghdl entry point added: you can start the VHDL simulation from your own program.

  • bug fix: - triple use. - incomplete types

[2003-04-07] 0.4.1#

  • bug fix: in the vcd output.

[2003-04-02] 0.4#

  • libgrt does not depend on GNAT library anymore. Installation requirements are reduced.

  • 'delayed attribute implemented.

  • 'transaction attribute implemented.

  • unaffected (from vhdl-93) implemented.

  • ghdl action --disp-standard prints the std.standard package.

  • exponentiation operator, **, implemented for all integer and floating point types.

  • many other small bug fixes.

  • bug fix: subprogram interfaces are now elaborated.