Welcome to my website! I am a researcher at Inria on testing and language implementations.https://guillep.github.io/https://guillep.github.io/blog/2026-09-04-exceptionshttps://guillep.github.io/blog/2026-09-04-exceptionsA personal journey from the familiar termination model of exceptions to Pharo's resumable exceptions—and why explicit callbacks can make better interfaces.Fri, 04 Sep 2026 00:00:00 GMThttps://guillep.github.io/blog/2026-08-07-overflowhttps://guillep.github.io/blog/2026-08-07-overflowA small tour of Pharo's stack, stack pages, recursion, and the surprisingly elegant way to make stack overflow less of a VM panic button.Fri, 07 Aug 2026 00:00:00 GMThttps://guillep.github.io/blog/2026-08-03-sandboxhttps://guillep.github.io/blog/2026-08-03-sandboxNotes from an ESUG'26 talk about the Pharo Sandbox.Mon, 03 Aug 2026 00:00:00 GMThttps://guillep.github.io/blog/2014-11-07-onion-pharohttps://guillep.github.io/blog/2014-11-07-onion-pharoExploring a minimal Pharo by layering it into phases, starting from the classes needed to run the class builder.Fri, 07 Nov 2014 00:00:00 GMThttps://guillep.github.io/blog/2014-01-23-replacing-bash-with-pharohttps://guillep.github.io/blog/2014-01-23-replacing-bash-with-pharoMaking Pharo act as a shell interpreter, with a custom command line handler to run Pharo scripts from the terminal.Thu, 23 Jan 2014 00:00:00 GMThttps://guillep.github.io/blog/2013-09-06-oz-object-spaces-in-esug-2013https://guillep.github.io/blog/2013-09-06-oz-object-spaces-in-esug-2013A summary of what was presented about Oz object spaces at ESUG 2013, plus links to the paper, the demo video and the new logo.Fri, 06 Sep 2013 00:00:00 GMThttps://guillep.github.io/blog/2013-08-26-recover-a-broken-image-with-ozhttps://guillep.github.io/blog/2013-08-26-recover-a-broken-image-with-ozUsing Oz object spaces to recover an image that crashes on startup, by loading it, inspecting the active process and fixing the offending literal.Mon, 26 Aug 2013 00:00:00 GMThttps://guillep.github.io/blog/2013-07-30-customizing-zeroconf-scriptshttps://guillep.github.io/blog/2013-07-30-customizing-zeroconf-scriptsA step-by-step guide to building your own ZeroConf scripts for custom Pharo images and VMs.Tue, 30 Jul 2013 00:00:00 GMThttps://guillep.github.io/blog/2013-07-23-installing-pharo-in-many-flavorshttps://guillep.github.io/blog/2013-07-23-installing-pharo-in-many-flavorsA summary of the many ways to install and deploy Pharo: manual downloads, the Ubuntu PPA, ZeroConf scripts and the Pharo Launcher.Tue, 23 Jul 2013 00:00:00 GMThttps://guillep.github.io/blog/2013-05-06-bootstrap-revival-the-basicshttps://guillep.github.io/blog/2013-05-06-bootstrap-revival-the-basicsRebuilding the Pharo bootstrap around object spaces, mirrors and an AST interpreter to overcome VM limitations.Mon, 06 May 2013 00:00:00 GMThttps://guillep.github.io/blog/2013-03-23-when-optimal-mattershttps://guillep.github.io/blog/2013-03-23-when-optimal-mattersOn premature optimization, why it is not the whole story, and how profiling helps you find the critical 3% of your code.Sat, 23 Mar 2013 00:00:00 GMThttps://guillep.github.io/blog/2013-03-19-keymappings-101-for-pharo-2-0https://guillep.github.io/blog/2013-03-19-keymappings-101-for-pharo-2-0A tutorial on the Keymappings library for Pharo 2.0: building key combinations, mapping them to shortcuts and attaching them to morphs.Tue, 19 Mar 2013 00:00:00 GMThttps://guillep.github.io/blog/2013-03-18-pharo-2-0-releasedhttps://guillep.github.io/blog/2013-03-18-pharo-2-0-releasedA tour of Pharo 2.0: new development tools, NativeBoost, Fuel, the Spec and Keymappings UI libraries, and a revamped internals.Mon, 18 Mar 2013 00:00:00 GMThttps://guillep.github.io/blog/2012-08-22-the-bootstrap-chronicles-the-end-of-a-phasehttps://guillep.github.io/blog/2012-08-22-the-bootstrap-chronicles-the-end-of-a-phaseWrapping up the GSOC 2012 bootstrap project: declarative kernel descriptions and the future of bootstrapping Pharo.Wed, 22 Aug 2012 00:00:00 GMThttps://guillep.github.io/blog/2012-06-30-the-bootstrap-chronicles-chapter-4https://guillep.github.io/blog/2012-06-30-the-bootstrap-chronicles-chapter-4Using Fuel to import packages and run SUnit tests on the bootstrapped image, plus a bootstrap-from-the-bootstrap experiment.Sat, 30 Jun 2012 00:00:00 GMThttps://guillep.github.io/blog/2012-06-17-smalltalk-behind-the-scenes-the-meta-modelhttps://guillep.github.io/blog/2012-06-17-smalltalk-behind-the-scenes-the-meta-modelHow the Smalltalk meta-model works and how you can build your own metaclass loop from scratch.Sun, 17 Jun 2012 00:00:00 GMThttps://guillep.github.io/blog/2012-06-17-the-bootstrap-chronicles-chapter-3-its-alivehttps://guillep.github.io/blog/2012-06-17-the-bootstrap-chronicles-chapter-3-its-aliveThe working bootstrap implementation: building a guest image inside a host one and reporting packaging and initialization bugs.Sun, 17 Jun 2012 00:00:00 GMThttps://guillep.github.io/blog/2012-06-11-the-bootstrap-chronicles-chapter-2-do-not-mess-with-the-vmhttps://guillep.github.io/blog/2012-06-11-the-bootstrap-chronicles-chapter-2-do-not-mess-with-the-vmThe VM restrictions that make bootstrapping hard: the special objects array, compact classes, primitives and the hacks used to work around them.Mon, 11 Jun 2012 00:00:00 GMThttps://guillep.github.io/blog/2012-06-08-the-bootstrap-chronicles-chapter-1-preparing-the-soilhttps://guillep.github.io/blog/2012-06-08-the-bootstrap-chronicles-chapter-1-preparing-the-soilFirst steps towards building a new Pharo image from scratch, adapting the SystemTracer and tracing packaging problems.Fri, 08 Jun 2012 00:00:00 GMThttps://guillep.github.io/blog/2012-06-02-bootstrapping-finding-the-missing-linkhttps://guillep.github.io/blog/2012-06-02-bootstrapping-finding-the-missing-linkAn introduction to the Pharo bootstrap project: what a bootstrap is, why Pharo needs one, and the current status of the GSOC effort.Sat, 02 Jun 2012 00:00:00 GMThttps://guillep.github.io/blog/2012-06-01-the-image-dilemmahttps://guillep.github.io/blog/2012-06-01-the-image-dilemmaComparing image-based and file-based development environments: configuration, development process and the tools each approach enables.Fri, 01 Jun 2012 00:00:00 GMThttps://guillep.github.io/blog/2012-05-30-understanding-object-formats-in-cogvmhttps://guillep.github.io/blog/2012-05-30-understanding-object-formats-in-cogvmHow Smalltalk objects are represented in the CogVM: object fields, headers, compact classes and immediate objects.Wed, 30 May 2012 00:00:00 GMT