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Compiling and using the Micro Virtual Machine

Building the micro virtual machine

The virtual machine is in directory MicroVM.

The main source file is microvm.c.

There are two supporting files utils_unix.c and utils_win.c depending on compiling for Unix or Windows based operating system.

To compile go to directory MicroVM and do below depending on platform

Mac x86 and Mx (ARM) platform with MacOS

gcc is clang by default and both work.

clang -Wall microvm.c -o microvm

or

gcc -Wall microvm.c -o microvm

On x86 platform with Linux

Both gcc and clang should work:

clang -Wall microvm.c -o microvm

or

gcc -Wall microvm.c -o microvm

On x86 platform with Windows

We recommend using clang as compiler.

There are two dependencies that much be installed:

  1. MSVC toolchain

Minimum choose "Visual Studio Build Tools".

  1. clang for Windows x86, llvm

Tested with image: LLVM-22.1.0-win64.exe

To compile:

clang --target=x86_64-pc-windows-msvc -Wall microvm.c -o microvm.exe

On ARM platform with Widnows

Not yet tested on ARM with Windows.

Simple test of micro-VM

The file prog0 prints an infinite number of numbers on terminal starting with commandline input:

./microvm prog0 10
10 11 12 13 14 15 16 ...

The file prog1 loops 20 million times

./microvm prog1          
Result value: 0 
Used 207 cpu milli-seconds
Number of GC: 0

Test the micro virtual abstract machine

The compiled micro-Java n-queens program, microJ/JavaEx/ex55.java, is included in the directory as file ex55.out.

Test the virtual abstract machine by running below examples

  1. With no command line arguments
./microvm
micro virtual machine for 64 bit architecture, running on MacOS
Compiled with clang version 17 on May 14 2026 at 12:14:11
Usage: microvm [-trace] [-silent] <programfile> <arg1> ...

You need to provide program to run, an *.out file.
  1. With ex55.out as command line argument
./microvm ex55.out 
Program expects 1 argument(s), but got 0.
Used 0 cpu milli-seconds
Number of GC: 0

The program ends asking for 1 command line argument, that is, the size of the board on which to place queens.

  1. With command line 5
./microvm ex55.out 5
1 3 5 2 4 
1 4 2 5 3 
2 4 1 3 5 
2 5 3 1 4 
3 1 4 2 5 
3 5 2 4 1 
4 1 3 5 2 
4 2 5 3 1 
5 2 4 1 3 
5 3 1 4 2 

10 

Result value: #52567225064 
Used 6 cpu milli-seconds
Number of GC: 0

There are 10 solutions.

The "Result value" is the top stack value when programs ends execution, bytecode STOP.

The micro virtual machine supports below command line arguments

  1. -silent

Will execute bytecode program in silence mode.

./microvm -silent ex55.out 5
1 3 5 2 4 
1 4 2 5 3 
2 4 1 3 5 
2 5 3 1 4 
3 1 4 2 5 
3 5 2 4 1 
4 1 3 5 2 
4 2 5 3 1 
5 2 4 1 3 
5 3 1 4 2 

10
  1. -trace

Will enable stack tracing and output stack after each bytecode has been executed.

./microvm -trace ex55.out 4
[ ]{0:PUSHLAB 774}
[ 774 ]{2:HEAPALLOC 1}
[ 774 #49949966336 ]{4:HEAPCOPY 1}
[ #49949966336 ]{6:LDARGS}
[ #49949966336 4 ]{8:VCALL 2 0}
[ 11 -999 #49949966336 4 ]{775:CSTI 0}
[ 11 -999 #49949966336 4 0 ]{777:GETBP}
[ 11 -999 #49949966336 4 0 2 ]{778:CSTI 2}
...
[ 11 -999 #34972106752 5 10 0 6 ... ]{2030:INCSP -1}
[ 11 -999 #34972106752 5 10 0 6 ... ]{2032:RET 10}
[ #34972119784 ]{11:STOP}

Result value: #34972119784 
Used 2058 cpu milli-seconds
Number of GC: 0

It is massive output and is practical usefull for small programs.

The micro virtual machine does not come with garbage collection.

But it is prepared for a mark and sweep collector as covered in Chapter 10 on Garbage Collection.

The relevant functions are

  • void collect(word s[], word sp): initiates collection.
  • void markPhase(word s[], word sp): marks live objects
  • void sweepPhase(): sweeps the heap memory address space and build new freelist.