The ICARUS Verilog Compilation System
Copyright 2000-2026 Stephen Williams
- What is ICARUS Verilog?
- Building/Installing Icarus Verilog From Source
- How Icarus Verilog Works
- Running iverilog
- Unsupported Constructs
- Nonstandard Constructs or Behaviors
- Credits
What is ICARUS Verilog?
Icarus Verilog is intended to compile ALL of the Verilog HDL, as
described in the IEEE 1364 standard. Of course, it's not quite there
yet. It also compiles a (slowly growing) subset of the SystemVerilog
language, as described in the IEEE 1800 standard. For a view of the
current state of Icarus Verilog, see its home page at
https://steveicarus.github.io/iverilog/.
Icarus Verilog is not aimed at being a simulator in the traditional
sense, but a compiler that generates code employed by back-end
tools.
For instructions on how to run Icarus Verilog, see the iverilog man page.
Building/Installing Icarus Verilog from Source
If you are starting from the source, the build process is designed to be
as simple as practical. Someone basically familiar with the target
system and C/C++ compilation should be able to build the source
distribution with little effort. Some actual programming skills are
not required, but helpful in case of problems.
Compile Time Prerequisites
You can use:
apt install -y autoconf gperf make gcc g++ bison flex
You need the following software to compile Icarus Verilog from source
on a UNIX-like system:
-
GNU Make
The Makefiles use some GNU extensions, so a basic POSIX
make will not work. Linux systems typically come with a
satisfactory make. BSD based systems (i.e., NetBSD, FreeBSD)
typically have GNU make as the gmake program.
-
ISO C++ Compiler
The ivl and ivlpp programs are written in C++ and make use
of templates and some of the standard C++ library. egcs and
recent gcc compilers with the associated libstdc++ are known
to work. MSVC++ 5 and 6 are known to definitely not work.
-
bison and flex
OSX note: bison 2.3 shipped with MacOS including Catalina generates
broken code, but bison 3+ works. We recommend using the Fink
project version of bison and flex (finkproject.org), brew version
works fine too.
-
gperf 3.0 or later
The lexical analyzer doesn't recognize keywords directly,
but instead matches symbols and looks them up in a hash
table in order to get the proper lexical code. The gperf
program generates the lookup table.
A version problem with this program is the most common cause
of difficulty. See the Icarus Verilog FAQ.
-
readline 4.2 or later
On Linux systems, this usually means the readline-devel
rpm. In any case, it is the development headers of readline
that are needed.
-
termcap
The readline library, in turn, uses termcap.
If you are building from git, you will also need software to generate the configure scripts.
-
autoconf 2.53 or later
This generates configure scripts from configure.ac. The 2.53
or later versions are known to work, autoconf 2.13 is
reported to not work.
Compilation
Unpack the tar-ball, cd into the verilog-######### directory,
and compile the source with the commands:
./configure
make
If you are building from git, you have to run the command below before
compiling the source. This will generate the "configure" file, which is
automatically done when building from tarball.
sh autoconf.sh
./configure
make
Normally, this command automatically figures out everything it needs
to know. It generally works pretty well. There are a few flags to the
configure script that modify its behaviour:
--prefix=<root>
The default is /usr/local, which causes the tool suite to
be compiled for install in /usr/local/bin,
/usr/local/share/ivl, etc.
I recommend that if you are configuring for precompiled
binaries, use --prefix=/usr. On Solaris systems, it is
common to use --prefix=/opt. You can configure for a non-root
install with --prefix=$HOME.
--enable-suffix
--enable-suffix=<your-suffix>
--disable-suffix
Enable/disable changing the names of install files to use
a suffix string so that this version or install can co-
exist with other versions. This renames the installed
commands (iverilog, iverilog-vpi, vvp) and the installed
library files and include directory so that installations
with the same prefix but different suffix are guaranteed
to not interfere with each other.
--host=<host-type>
Compile iverilog for a different platform. You can use:
x64_64-w64-mingw32 for building 64-bit Windows executables
i686-w64-mingw32 for building 32-bit Windows executables
Both options require installing the required mingw-w64 packages.
(Optional) Testing
To run a simple test before installation, execute
make check
The commands printed by this run might help you in running Icarus
Verilog on your own Verilog sources before the package is installed
by root.
This is the beginning of the README. Read the rest at the original. Read the full README ↗
