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HDL Checker
Python PowerShell VHDL Shell Dockerfile SystemVerilog Verilog
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HDL Checker

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HDL Checker is a language server that wraps VHDL/Verilg/SystemVerilog tools that aims to reduce the boilerplate code needed to set things up. It supports Language Server Protocol or a custom HTTP interface; can infer library VHDL files likely belong to, besides working out mixed language dependencies, compilation order, interpreting some compilers messages and providing some (limited) static checks.


pip install hdl-checker

Editor support

Editor Info
Vim Out of the box via dense-analysis/ale, other LSP clients should work
VSCode HDL Checker HDL Checker VSCode client


HDL Checker server can be started via hdl_checker command. Use hdl_checker --help for more info on how to use it.

$ hdl_checker -h
usage: hdl_checker [-h] [--host HOST] [--port PORT] [--lsp]
             [--attach-to-pid ATTACH_TO_PID] [--log-level LOG_LEVEL]
             [--log-stream LOG_STREAM] [--stdout STDOUT]
             [--stderr STDERR] [--version]

optional arguments:
  -h, --help            show this help message and exit
  --host HOST           [HTTP] Host to serve
  --port PORT           [HTTP] Port to serve
  --lsp                 Starts the server in LSP mode. Defaults to false
  --attach-to-pid ATTACH_TO_PID
                        [HTTP, LSP] Stops the server if given PID is not
  --log-level LOG_LEVEL
                        [HTTP, LSP] Logging level
  --log-stream LOG_STREAM
                        [HTTP, LSP] Log file, defaults to stdout when in HTTP
                        or a temporary file named hdl_checker_log_pid<PID>.log when
                        in LSP mode
  --stdout STDOUT       [HTTP] File to redirect stdout to. Defaults to a
                        temporary file named hdl_checker_stdout_pid<PID>.log
  --stderr STDERR       [HTTP] File to redirect stdout to. Defaults to a
                        temporary file named hdl_checker_stderr_pid<PID>.log
  --version, -V         Prints hdl_checker version and exit

Third-party tools

HDL Checker supports

Configuring HDL Checker

See the Setting up a new project section on the wiki.

LSP server

HDL Checker has beta support for Language Server Protocol. To start in LSP mode:

hdl_checker --lsp

On a Linux system, log file will be at /tmp/hdl_checker_log_pid<PID_NUMBER>.log and /tmp/hdl_checker_stderr_pid<PID_NUMBER>.log.

HTTP server

HDL Checker can be used in HTTP server mode also:


Please note that this mode does not use LSP to communicate. Request/response API is not yet available, but a reference implementation can be found in vim-hdl


HDL Checker uses a docker container to run tests. If you wish to run them, clone this repository and on the root folder run


The container used for testing is suoto/hdl_checker_test

Supported systems

System CI CI status
Linux Yes Build Status
Windows Yes Build status

Style checking

Style checks are independent of a third-party compiler. Checking includes:

  • Unused signals, constants, generics, shared variables, libraries, types and attributes
  • Comment tags (FIXME, TODO, XXX)

Notice that currently the unused reports has caveats, namely declarations with the same name inherited from a component, function, procedure, etc. In the following example, the signal rdy won't be reported as unused in spite of the fact it is not used.

signal rdy, refclk, rst : std_logic;

idelay_ctrl_u : idelay_ctrl
    port map (rdy    => open,
              refclk => refclk,
              rst    => rst);


You can use the issue tracker for bugs, feature request and so on.


This software is licensed under the GPL v3 license.


Mentor Graphics®, ModelSim® and their respective logos are trademarks or registered trademarks of Mentor Graphics, Inc.

Intel® and its logo is a trademark or registered trademark of Intel Corporation.

Xilinx® and its logo is a trademark or registered trademark of Xilinx, Inc.

HDL Checker's author has no connection or affiliation to any of the trademarks mentioned or used by this software.

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