fidzu : software

Last week at Drupal South, Pamela Barone delivered a keynote on Drupal CMS. Her talk is one of the clearest articulations I've seen of what Drupal CMS is, why it exists, and where it's headed. That shouldn't come as a surprise because Pam is the Product Lead for Drupal CMS.

Pam quoted a familiar Drupal saying: Drupal makes hard things possible, but it also makes easy things hard.. The room laughed because it's true.

Her keynote was about how Drupal CMS is helping to fix that. Drupal CMS is making Drupal easier to learn, easier to use, and easier to sell, without removing any of Drupal's power and flexibility. It brings visual page editing, a smoother path for new developers, and better project economics.

And these improvements are not just interesting for smaller projects. Universities, governments, and large enterprises want the same benefits. That is why Drupal CMS matters at every scale.

Pam also explains how Drupal CMS sits on top of Drupal Core, why it is not a Drupal distribution, how it gives digital agencies leverage, what site templates unlock, and how Drupal Canvas reshapes the page building experience.

If you watch one Drupal video this week, make it Pam's!

31 May 2026 5:00pm GMT

I saw two thoughtful posts in my LinkedIn feed over the last week that I wanted to reshare here before the LinkedIn feed buried them. Both were spot on, honest, and deserve a longer shelf life.

The first was from Hynek Naceradsky:

I'm pissed.

Not at Drupal. At the people confidently hating on it without ever having understood what it actually does.

"Drupal is outdated." "Drupal is too complex." "Nobody uses Drupal anymore."

Tell that to the EU institutions, governments, universities, and enterprises quietly running mission-critical platforms on it.

Here is what actually gets me though: the Drupal community lets this narrative win.

I am guilty of this too.

We literally have thousands of contributed modules, maintained for free, by people who owe you absolutely nothing. The security team responds faster than most paid vendors. The community has been showing up for 20+ years.

And yet we're somehow losing the PR war to frameworks that can't handle a proper content workflow without three paid plugins and a prayer.

Drupal people: talk louder. Write the posts. Go to the meetups. Tell the stories, fight for Drupal.

Because the Drupal community is honestly the best thing in Open Source, and both it and Drupal deserve way better than silence.

The second was from Thomas Scola, writing from a Drupal AI event in New York (lightly trimmed):

I overheard a couple people say, "Drupal? Is that still around?"

Hell yes it is.

And not only is it still around, I'd argue pretty heavily that Drupal is uniquely positioned for what comes next with the agentic web.

API-first before API-first was cool and trendy. Structured content that actually makes sense. Mature permissions, workflows, governance, integrations.

A lot of platforms are now scrambling to figure out how AI fits into what they already built.

Drupal doesn't have to force it. The architecture has been there.

But honestly, the tech is only part of it. The community is what always gets me. The people, passion and innovation. [...]

What comes next? Who knows.

But if I'm betting on a community to adapt, build, and help define that future, I'm putting my money on this one, and on what we've all built together.

For a platform people love to ask if it's "still around", it feels more relevant than ever.

I could not agree more with both posts. Drupal is one of the strongest Open Source platforms out there right now, but too few people realize it. The Drupal community has been modernizing the platform faster than its reputation evolves.

If the loudest narrative about Drupal is that it is outdated, people will keep repeating it, even when it is wrong. AI systems will too, because they absorb the same narratives, blog posts, forum threads, and social media the rest of the industry does.

The danger is not just that Drupal is misunderstood today. It's that the gap between perception and reality may be growing, not shrinking.

The narratives we reinforce today become part of how AI describes Drupal tomorrow. The Drupal community's silence today becomes tomorrow's AI consensus.

So if you're in the Drupal community, take Hynek's advice and help set the record straight. Not for AI, but for people. Write about the great work happening in Drupal: share the case studies, the technical breakthroughs, the AI innovation, the shared learnings, and the hard problems being solved every day.

We need to spend a lot more time explaining where Drupal fits, the kinds of problems it solves well, and why so many organizations believe in Open Source and the Drupal community.

I know many people in Open Source dislike marketing or self-promotion. I do too, sometimes. But if we don't document what is great about Drupal, others will define Drupal for us.

Every accurate case study, technical blog post, demo, presentation, or community success story helps future developers, evaluators, and AI systems understand what Drupal actually is.

Drupal does not need hype. It needs a better public record.

31 May 2026 5:00pm GMT

In Open Source software, competition works differently than in proprietary software.

Companies compete through their own products and services, but they all depend on the same commons: the software, the community, the project's reputation, and the shared work that helps people trust and adopt it.

That shared foundation creates a different kind of responsibility: sharing a commons means sharing the work of keeping it strong.

The Open Source companies I admire most show up in two ways. They compete on the merits of their own products: features, support, and price. And they help sustain the commons: through code, documentation, security, marketing, events, education, sponsorships, and more.

Judge companies by what they do

Over the past year, Pantheon, one of Acquia's competitors in the Drupal market, has focused much of its messaging on attacking Acquia, including making our private equity ownership part of its story.

I have no quarrel with Pantheon's products or the people who build them. Competition is healthy. My concern is with marketing that attacks another Drupal company, often with misleading or unwarranted messaging.

I've spent nearly twenty years building Acquia through different stages and ownership models. Acquia has grown from a startup into a company backed first by venture capital and later by private equity. Every ownership model creates different pressures, but ownership determines far from everything.

Customers don't choose a platform because of an ownership model. They choose it because it works, because they can get help, and because they trust the platform will keep getting better. In Open Source, that trust depends on the health of the commons behind it.

Customers, partners, community members, and end users are not helped by vendor attacks. They are helped when companies build better products, contribute to Drupal, and help more people adopt it.

License permits, stewardship grows

For an Open Source company, the test is not only what they build for themselves. It is what they help build for everyone.

An Open Source license defines what companies are allowed to do. It sets the floor. Contribution is not required.

Above that floor is a social contract. No one enforces it, but every healthy Open Source ecosystem depends on it.

Stewardship is what companies choose to do beyond the license: contribute code, fund security work, support maintainers, improve documentation, sponsor events, promote adoption, and more.

Drupal thrives because people and organizations honor the social contract and choose to do more than the license requires.

Contribution is one measure of stewardship

Drupal.org credit is one public signal of that commitment. Acquia is the largest single corporate contributor to Drupal, but the wider community contributes far more than any one company.

In the past year, Acquia engineers earned 26,331 weighted issue credits, plus 164 from the Drupal Security Team.

These contributions are good for Acquia, for Drupal, and for every organization that builds on Drupal, including our competitors.

In the same period, Pantheon earned 243 weighted issue credits, plus 2 security credits. Credits don't capture every form of contribution, and Pantheon contributes in other ways too. Even so, the gap is substantial.

What we let pass becomes the social contract

I don't usually write publicly about competitors. It's not how I want to spend my voice.

Before writing this, I asked myself a simple question: if a major company contributing to Drupal were under sustained attack from another major Drupal company, would I feel a responsibility as Drupal's founder and project lead to speak up?

I would.

The fact that Acquia is the company being attacked made me slower to respond, but it doesn't change the answer.

When companies built on Drupal spend their energy attacking each other instead of growing the project, it bothers me. It's not good for Drupal.

I'm not writing this believing it will change anyone's marketing and sales tactics. I'm writing it because what we let pass now will shape what is acceptable in Drupal years from now.

Communities like ours evolve their social contract through moments like this, when we say in public what we expect of each other. If this post contributes to a healthier social contract taking hold, I'm happy.

Compete on merit, but grow the commons

Every company that builds on Drupal depends on the same commons. Every company has a choice about whether to help sustain it, and how much. Drupal gets stronger when more of us invest in it.

My invitation to every company that builds on Drupal is simple: let's compete on the merits of our products and services, not by attacking each other. Let's serve customers well, contribute where we can, and put our energy into helping more organizations choose Drupal in the first place.

That is the social contract I'd like all of us to live by. I want Acquia to be judged by that same standard: what we ship, how well we serve customers, how much we contribute, and whether Drupal is stronger because of our work.

Not by who owns us. Not by claims made about us. By whether we keep building, contributing, and helping the ecosystem grow.

I have said what I wanted to say, and I won't turn this into an ongoing debate or respond to social media comments on this. My focus is on building and contributing.

31 May 2026 5:00pm GMT

Ron Garrett wrote an interesting blog post about the mathematical possibility of abiogenesis [1].

Cory Doctorow wrote an interesting blog post about the way the current antics of right wing extremists are forcing permanent changes in society away from the old systems [2].

William Angel wrote an insightful blog post comparing the costs of a Macbook and the Openrouter hosted service for LLMs [3].

The Register has an informative article about the threat that management systems built in to Intel and AMD CPUs pose to data sovereignty in EU owned cloud providers [4]. But this is just the first stage of building sovereign clouds, all significaant cloud services run at least 2 types of CPU and adding EU manufactured CPUs at a future time will be easy.

Benn Jordan made an interesting YouTube video about the infrasound problems caused by data centers, we need FOSS to measure infrasound [5].

amarok on the Purism forum made a great post about how to setup profiles in Firefox for different uses [6].

fralb5 wrote an informative post on the Purism forum about how to use a Librem 5 (or any other FOSS Linux phone) to firewall spyware on an Android phone [7].

Michael Prokop wrote an interesting blog post about debugging input event problems on Linux which turned out to be due to an analogue headphone connection [8]. This gave me some useful pointers to investigating an input device problem which is probably very different.

Patrick Boyle made an insightful youtube video about the ridiculous IPO of SpaceX, it seems like a scam from start to finish [9].

Anarcat wrote an insightful blog post about the LLM apocalypse comparing it to the horsemen of the apocalypse [10].

The Wikimedia Foundation (that runs wikipedia.org among other things) is sacking union organisers and trying to corporatise the organisation which means stealing the donations from the community [11].

Tianon Gravi wrote an informative blog post about containers, Debian, and Docker options [12]. We need a lot more work on these sorts of things in Debian.

Memory Tagging and how it improves C/C++ memory safety is an interesting paper from Google researchers giving an overview of the benefits of tagged memory hardware for pointer validation on SPARC and ARM64 [13].

In 2013 a faulty beer fridge motor acted as a spark gap transmitter and blocked mobile phone service for several Melbourne suburbs [14].

• [1] https://tinyurl.com/25p5w844
• [2] https://pluralistic.net/2026/04/20/praxis/#acceleration
• [3] https://tinyurl.com/2az3uazq
• [4] https://tinyurl.com/26aygdv6
• [5] https://www.youtube.com/watch?v=_bP80DEAbuo
• [6] https://tinyurl.com/yvnszuyh
• [7] https://tinyurl.com/ymmcpt9t
• [8] https://tinyurl.com/2859uflr
• [9] https://www.youtube.com/watch?v=IHD8BDFYyGI
• [10] https://anarc.at/blog/2026-05-16-four-horsemen/
• [11] https://tinyurl.com/26mhk6ok
• [12] https://tinyurl.com/2dba3jut
• [13] https://arxiv.org/pdf/1802.09517
• [14] https://tinyurl.com/2cfo3nsa

31 May 2026 12:08pm GMT

Metaobject Protocol (MOP) Implementation in CLRHack

The Metaobject Protocol in CLRHack is a high-performance implementation of the Common Lisp Object System (CLOS) integrated into the .NET 8.0 Common Language Runtime (CLR). It provides a complete meta-compilation pipeline that bridges the gap between dynamic Lisp semantics and the static CIL (Common Intermediate Language) execution model.

Core Architecture

The MOP is implemented through three primary layers:

1. The Metaobject Hierarchy (C#): A set of foundational classes in LispBase representing classes, methods, generic functions, and slot definitions.
2. The Runtime Engine (MopRuntime): A centralized orchestrator that manages class finalization, method combination, dispatch caching, and instance allocation.
3. The Compiler Bridge (Lisp): Transformations in ast.lisp that translate high-level CLOS forms (defclass, defmethod) into optimized runtime calls.

Instance Representation

Because the CLR type system is strictly single-inheritance and statically defined, CLRHack decouples Lisp-level inheritance from C# inheritance. All CLOS instances are represented by the StandardObjectInstance class, which contains:

• A reference to its ClassMetaobject.
• A private object[] storage array for instance slots, indexed by locations calculated during class finalization.

The Dispatch Pipeline

Generic function invocation is the most complex part of the implementation. When a generic function is called:

1. Cache Lookup: The DiscriminatingFunction first checks a thread-safe dispatchCache using an InvocationCacheKey (a stack-allocated struct) to find a previously computed effective method.
2. Applicability & Precedence: If the cache misses, the runtime computes all applicable methods and sorts them based on specializer specificity and the Class Precedence List (CPL).
3. Method Combination: The ComputeEffectiveMethod logic builds a nested execution chain following the Standard Method Combination rules:
   • :around methods are called first, with call-next-method progressing to the next around method or the main chain.
   • The main chain executes all :before methods, the primary method, and finally all :after methods in reverse order.
4. Fast Invocation: The resulting effective method is compiled into a Func<object[], object> that uses direct delegate invocation to minimize overhead.

Challenges and Solutions

1. Thread-Safe Non-Local Exits (call-next-method)

Challenge: call-next-method and next-method-p require access to the current invocation's state (the remaining methods and original arguments). Passing this state through every function call would break compatibility with standard Lisp function signatures.

Solution: CLRHack utilizes [ThreadStatic] fields in MopRuntime to store the currentNextMethods and currentArguments. This ensures that even in highly concurrent environments (like a web server), each OS thread has its own isolated invocation context, allowing call-next-method to function correctly without state leakage.

2. Forward References and Lazy Finalization

Challenge: Lisp allows classes to refer to superclasses that haven't been defined yet. The runtime must handle these "zombie" classes without crashing the JIT compiler.

Solution: The system implements a ForwardReferencedClassMetaobject. When a class is defined, it is automatically finalized (computing its CPL and slot layout). If a superclass is missing, a forward reference is created. The EnsureFinalized protocol ensures that inheritance is resolved and slot locations are assigned the moment the class is first instantiated or used in dispatch.

3. Performance Overhead of the "MOP Bridge"

Challenge: A naive implementation of slot-value or generic dispatch using C# reflection or linear searches is orders of magnitude slower than native C# member access.

Solution: Three distinct optimizations were applied:

• O(1) Slot Access: Each ClassMetaobject maintains a SlotDictionary. Slot names are mapped to physical array indices during finalization, allowing slot-value to perform a direct array access after a single dictionary lookup.
• Compiler Primitives: The compiler identifies SLOT-VALUE and MAKE-INSTANCE calls and emits direct CIL call instructions to optimized Lisp.MopRuntime methods, bypassing the general Funcall path.
• Zero-Allocation Cache Hits: By making InvocationCacheKey a readonly struct and avoiding the cloning of the argument array during cache probes, the hot-path for generic function dispatch generates zero garbage for the .NET Collector.

4. Bootstrapping the COMMON-LISP Package

Challenge: Core CLOS functions like make-instance must be available as symbols in the COMMON-LISP package before user code runs, but they rely on the MOP runtime being fully initialized.

Solution: A MopRuntime.Initialize() method is injected into the entry point (Main) of every generated assembly. This method interns the necessary symbols and binds them to GenericFunctionClosureAdapter objects, ensuring that the MOP is "alive" before the first line of Lisp code executes.

---

Vibe coding the MOP basically involved feeding chapters 4 and 5 of the Art of the Meta-Object Protocol into the LLM and telling it to make an implementation plan. It came up with a twenty-step plan to bootstrap CLOS. I then spent the rest of the day instructing an agent to take on each task of the twenty-step plan in sequential order. At the end of the day, I had a working MOP

This is the end of my series of posts on CLRHack.

31 May 2026 7:00am GMT

Implementation of SIGNAL and ERROR in CLRHack

In CLRHack, the condition signaling system is implemented in the Lisp.HandlerControl class within the LispBase library. It leverages .NET's [ThreadStatic] storage to maintain a per-thread dynamic stack of active condition handlers.

SIGNAL Implementation

The Signal(object condition) method performs the following logic:

1. Retrieval: It fetches the activeHandlers list for the current thread. This list is a chain of [LispBase]Lisp.Handler objects maintained by handler-bind.
2. Iteration: It iterates linearly through the list from the most recently bound handler to the oldest.
3. Type Matching: For each handler, it calls IsType(condition, handler.ConditionType).
   • If the condition is a symbol, it checks for symbol equality (supporting simple symbol-based conditions).
   • If the condition is a .NET object, it checks if the handler's type is assignable from the condition's runtime type (supporting interop with system exceptions).
   • It treats the symbols T or EXCEPTION as catch-all types.
4. Handler Invocation: If a match is found:
   • Recursive Signal Protection: Before calling the handler function, the current handler list is temporarily shadowed. activeHandlers is set to cell.rest (the handlers bound outside the current one). This ensures that if the handler itself calls signal, it won't trigger itself recursively.
   • Execution: The handler's Closure is invoked with the condition object as its argument.
   • Restoration: A finally block ensures the original activeHandlers list is restored if the handler returns normally.

   ERROR Implementation

   The Error(object condition) method build upon Signal:

   1. Signaling Pass: It first invokes Signal(condition). If a handler performs a non-local exit (e.g., via handler-case), the Error method never returns.
   2. Debugger Entry: If Signal returns normally (meaning all handlers declined), Error calls EnterDebugger(condition).
   3. Interactive Debugging: The debugger:
      • Prints the condition and a list of available restarts (retrieved via RestartControl.GetActiveRestarts()).
      • Provides a prompt for the user to select a restart, launch the system-level debugger (Visual Studio/Rider), or abort.
      • If a restart is selected, it is invoked interactively (potentially gathering arguments from the user).
   4. Final Fallback: If the debugger is exited without invoking a restart, Error throws a C# Exception to ensure that execution does not continue on an invalid path.

   Notable Implementation Decisions and Edge Cases

• Handler Shadowing: The decision to pop the handler list during invocation is critical for maintaining Common Lisp semantics. It prevents infinite loops and ensures that "outer" handlers can handle errors raised within "inner" handlers.
• Unified Exception Model: CLRHack attempts to unify Lisp conditions and .NET exceptions. IsType allows Lisp handlers to catch C# exceptions by their class name or Type object.
• Thread Isolation: By using [ThreadStatic] for activeHandlers, CLRHack ensures that condition signaling is thread-safe. One thread signaling an error will not interfere with the handler state of another thread.
• Debugger Capability: The SYSTEM-DEBUGGER option in EnterDebugger is a bridge to the underlying .NET environment, allowing developers to use professional IDE tools to inspect the state of the Lisp VM when an unhandled error occurs.

signal and error complete the Common Lisp condition system implementation for CLRHack

30 May 2026 7:00am GMT

Armadillo is a powerful and expressive C++ template library for linear algebra and scientific computing. It aims towards a good balance between speed and ease of use, has a syntax deliberately close to Matlab, and is useful for algorithm development directly in C++, or quick conversion of research code into production environments. RcppArmadillo integrates this library with the R environment and language-and is widely used by (currently) 1272 other packages on CRAN, downloaded 46.6 million times (per the partial logs from the cloud mirrors of CRAN), and the CSDA paper (preprint / vignette) by Conrad and myself has been cited 693 times according to Google Scholar.

This versions updates to the 15.2.7 upstream Armadillo release made today. The package has already been updated for Debian, and built for r2u. As the upstream was modest, we for once skipped reverse-dependency checks. That bet paid off as CRAN found no issues among the over 1270 reverse dependencies. However, one package referenced a package archived today, hence 'invisible' to CRAN and triggered a (false positive) NOTE of 'reference to non-existing package'. We came close. Anyway, the package made it CRAN shortly thereafter following the standard brief email exchange explaining the false-positive nature of the NOTE.

All changes since the last CRAN release follow.

Changes in RcppArmadillo version 15.2.7-1 (2026-05-29)

• Upgraded to Armadillo release 15.2.7 (Medium Roast Deluxe)

  • More efficient checks for aliasing

Courtesy of my CRANberries, there is a diffstat report relative to previous release. More detailed information is on the RcppArmadillo page. Questions, comments etc should go to the rcpp-devel mailing list off the Rcpp R-Forge page.

This post by Dirk Eddelbuettel originated on his Thinking inside the box blog. If you like this or other open-source work I do, you can sponsor me at GitHub. You can also sponsor my Tour de Shore 2026 ride in support of the Maywood Fine Arts Center.

29 May 2026 9:48pm GMT

In September 2025, I attended the annual LibreOffice conference in Budapest, Hungary. This gave me an opportunity to explore the city, which I will cover in this post.

Let's start with the currency. Although Hungary is a part of the European Union (EU), it doesn't use the euro as its currency. Instead, it uses Hungarian forints (denoted by "Ft"). During my time in Hungary, 1 Indian rupee was equal to 4 Hungarian forints.

After reaching the Budapest airport, I bought a 15-day public transport pass. The public transport counter is after you pass customs and immigration. The pass allows unlimited use of public transport in the city. I had to show my passport and pay 5950 Ft to get the pass. The pass had my passport number mentioned on it. The public transport passes can also be bought at any of the tram stations as well.

This is the counter from where I bought my public transport pass.

My unlimited public transport pass for Budapest. I have redacted my passport number from it.

An automatic ticket machine at a tram station in Budapest.

Budapest is a union of two cities-Buda and Pest-lying on opposite sides of the Danube River. My hotel-Corvin Hotel-was on the Pest side.

Budapest had good public transport. The buses, metros, and trams complemented each other. For example, the airport didn't have metro or tram connectivity, but it was served by the bus. Most of the metro was on the Pest side, with only a couple of stations falling in Buda. However, both sides had an extensive network of trams.

Furthermore, the information about the public transport was easily accessible. For instance, the map of tram stops inside the trams also included the bus routes one could get after alighting at those stops.

From the airport, I took a bus followed by taking a metro on the M3 line to reach within walking distance of my hotel.

An M3 line metro in Budapest.

During the conference I would take the tram to the conference venue. The trams were modern and fast. They also had a smiley face at the front, which gave them a friendly look. It seemed like the trams were happily doing their job. The city also had a good pedestrian infrastructure along with separate cycling tracks.

A tram in Budapest having a smiley face at the front.

Budapest's tap water is officially safe to drink, which was mentioned on a sticker posted on the wall of the bathroom of my hotel room. So, I did not need to buy any water bottles while I was there.

On the 6th of September, I went on a sightseeing tour of Budapest with my Dione. Our friend Attila, who was a local (from Hungary), joined us. We went to the central market from our hotel by metro.

If you read my post on Vienna, I mentioned that the metro stations don't have AFC gates but ticket validators instead. Budapest's metro also has the same system. If you buy individual tickets, you need to validate them using the validators on the station before boarding the metro. If you are using a public transport pass like I was, then you do not need to validate, and you can board the metro directly.

A ticket validator at a metro station in Budapest.

In 10-15 minutes, we reached the central market. Attila showed us around. I bought a fridge magnet and paprika powder as souvenirs. Paprika powder is a signature spice of Hungary. It is mainly available in two forms-one is sweet and the other being spicy. I wanted the spicy one, but I didn't get that in that market. Therefore, I had to contend with buying the sweet version. The sweet version isn't sweet though, it is just not spicy. After bringing that paprika powder home, it is mainly used for food coloring. I like it though and use it frequently in my omelets and other dishes.

Central market.

The building right behind the tram is the central market building.

At some point, Atilla had to join the The Document Foundation (TDF) sightseeing group, so we parted ways at the central market. Dione and I continued our sightseeing and decided to start with visiting the Hungarian parliament, which is a tourist attraction. It was because we were on the Pest side and the parliament was also on the same side, while other tourist attractions were on the Buda side.

So, Dione and I hopped on a tram and went to the parliament. We got off at a tram station just outside the parliament. The parliament is the icon of Budapest. The building has a gothic architecture and colored brown and white. One can buy tickets and take an inside tour. However, we didn't have a lot of time, so we stayed outside the building.

Hungarian Parliament building.

After spending some time outside the parliament building, we took a tram to the Chain Bridge. As I mentioned earlier, Budapest has two parts-Buda and Pest-separated by the Danube River. To go from one of the sides to the other requires crossing a bridge. Although Budapest has many bridges linking the two sides, the main one is the Chain Bridge.

We walked on the chain bridge to get to the other side. The bridge gave a good view of the Danube River. It also had a statue of a lion. The Buda Castle (another major landmark of Budapest) was visible from the bridge.

A shot of Chain Bridge.

The lion statue on the Chain Bridge.

After reaching the other side of the bridge (the Buda side), we sat on a bench for some time and then planned on where to go next. We decided to go to Fisherman's Bastion, which is another tourist attraction.

We used the OSMAnd~ app to figure out which bus to take and hopped on one. Soon we reached Fisherman's Bastion, where we found a flight of stairs that led upwards. Upon climbing the stairs, we got a panoramic view of the city. It also gave us a good view of the Hungarian parliament across the river. Going further upstairs, we found a statue of Stephen I of Hungary. He was the first king of Hungary, getting the crown in the year 1900.

A view of Hungarian parliament from Fisherman's bastion.

I found Fisherman's Bastion to be the best tourist attraction in the city. As mentioned earlier, it offers a panoramic view of the city, which I liked. I liked the arhitecture and open space there. If you find yourself in Budapest, I would highly recommend that you visit Fisherman's Bastion.

Fisherman's Bastion.

Statue of Stephen I of Hungary at Fisherman's Bastion.

Next, we went downstairs and returned to where the bus dropped us. From here on, we walked in random streets to see the residential and non-touristy side of Budapest. It was not so random as we walked towards Batthyány tér metro station. Upon reaching the metro station, we found a café where we stopped for a while for some coffee. After injecting some caffeine into our blood, we proceeded to find a place to have lunch.

Batthyány tér metro station.

For lunch, we decided to go to Rákóczi tér metro station after reading on the internet about the food options there. Upon exiting the metro station, we found a market inside a building that had a lot of shops, but most of them were closed.

After roaming around inside a bit, we found an Italian place open and decided to eat there. The name of this place was Matteos. We ordered an eggplant parmigiana, a lasagna artichoke, and a classic tiramisu. It wasn't very tasty but filled us up for the day.

A picture of Matteos, where we had our lunch.

Budapest has four metro lines, and we had been to three of them, so we decided to try the remaining line, which was the M1 line. It is the oldest line in the city and has a different vibe than the modern lines. This line was opened in 1896, one of the oldest subway systems in the world.

The coaches were much smaller than the other metro lines, and the seating arrangement was something you would expect from a bus than a typical metro train. We rode all the way to the last stop, Mexikói út. Upon going outside, we found out there wasn't much to do here.

At this point, I checked the map and realized that Heroes' Square is just a couple of metro stations away. Heroes' Square is a tourist attraction in Budapest. It is located in Zuglóa and is a historically significant place in Budapest. It has a monument which features the Seven chieftains of the Magyars.

M1 line station and tracks. It is the oldest metro transit of Budapest and one of the oldest in the world. It started operations in 1896.

Here, our unlimited public transport pass was handy because if it was paid per trip, we would think of the stop as a "wasted" one because we would have to buy a ticket again, but in this case we could just hop on again without any regrets.

An M1 line metro train entering the station.

So we took the M1 line again and deboarded at Hősök tere station, followed by walking to the square. After roaming around for a while, we saw a trolleybus and decided to ride on that.

Heroes' Square.

This is the trolleybus we took in Budapest.

A trolleybus is an electric bus that is powered by overhead electric cables. It is like a tram but runs on roads instead of tracks. We got down at Dózsa György út metro station. Then we took a metro to our hotel.

Before going to the hotel, we went to a place to eat something. We had coffee and lángos. Lángos is a deep-fried Hungarian dish, which looks exactly like the Indian flatbread bhatura. I found it tasty, but since it was deep-fried, that was almost a given.

Lángos - a dish which looks like the Indian flatbread bhatura.

The next day we went to Vienna-the capital of Austria-which I have already posted about. Check it out here.

I had a good time in Budapest, and it is a beautiful city with good public transport and some amazing sites to visit. That's it for now, and see you next time!

Credits: Thanks Dione and Badri for proofreading.

29 May 2026 2:26pm GMT

In the CLRHack compiler, handler-bind is a primitive form used to register condition handlers in the dynamic environment. It operates by managing a thread-local list of active handler objects, ensuring that condition signaling follows the standard Common Lisp search and execution rules.

Handling of handler-bind

When the compiler processes a handler-bind form, it generates CIL code that performs the following steps:

1. Capture Previous State: It calls Lisp.HandlerControl::GetActiveHandlers() to retrieve the current list of active handlers and stores it in a frame-local variable.
2. Construct New List: For each binding, it evaluates the condition type and the handler function (which is typically a closure). It instantiates a new [LispBase]Lisp.Handler object and conses it onto the current handler list.
3. Install New State: It calls Lisp.HandlerControl::SetActiveHandlers(new_list) to update the dynamic environment for the current thread.
4. Protected Execution: The body of the handler-bind is wrapped in a CIL .try block.
5. Restoration: A finally block is emitted that calls SetActiveHandlers with the saved list. This ensures that handlers are properly uninstalled, regardless of whether the body completes normally, signals an error, or performs a non-local exit.

Lexical Non-Local Exits

Handlers in Common Lisp are executed in the dynamic environment of the signaller but have lexical access to the environment where they were defined. In CLRHack, if a handler function performs a non-local exit (such as a throw or return-from), the compiler utilizes its exception-based jump mechanism:

• If the exit is a throw, it uses the standard CatchThrowException mechanism.
• If the exit is a return-from to a block outside the handler closure, the compiler identifies this as a non-local exit during analyze-environment. It compiles the return-from into a throw of a BlockExitException, which is subsequently caught by the try/catch frame established by the target block.

Handler Search

The handler search is performed at runtime by the signal or error functions. These functions retrieve the active handlers list via HandlerControl.GetActiveHandlers() and iterate through them. For each handler, the runtime checks if the signaled condition is of the type (or a subtype of the type) the handler was registered for. If a match is found, the handler function is invoked. If the handler returns normally (declines), the search continues with the next applicable handler.

Dynamic Tags

The handler-bind implementation itself relies on the dynamic state of the thread-local activeHandlers list. However, when used in conjunction with handler-case, unique dynamic tags (typically fresh ListCell objects) are generated. These tags are used as the "target" for the throw performed by the handler, ensuring that the control flow returns exactly to the correct handler-case frame and doesn't conflict with other active handler or catch frames.

handler-case as an Extension of handler-bind

In CLRHack, handler-case is not a primitive but a macro that expands into a combination of block, catch, and handler-bind. It extends handler-bind by providing a mechanism to automatically exit the signaling context and execute a specific branch of code based on the condition caught.

The implementation details of the expansion are as follows:

• Exit Block: The entire form is wrapped in a block with a unique exit tag to allow the normal path to return immediately upon completion of the protected expression.
• Dynamic Setup: A unique dynamic tag is created for the catch frame. Local variables are established to store the captured condition and a unique ID identifying which clause was triggered.
• The Binding: A handler-bind is generated where each handler function is a closure that, when called:
  1. Saves the signaled condition into the local condition-var.
  2. Sets the id-var to a unique GENSYM representing that specific clause.
  3. Performs a throw to the dynamic tag.
• The Catch and Dispatch: A catch block surrounds the protected expression. If a handler performs the throw, the catch returns, and a cond statement (the dispatcher) checks the id-var. It then executes the body of the matching handler-case clause with the condition variable bound to the clause's parameter.

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