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I don't understand the second part. Can someone explain it to me?
Ooh, fond (and some not so fond) memories of when Silicon Graphics' (MIPS) C and C++ compilers were based on EDG's frontend, with a custom ucode-generating backend, and integrated into CASEVision. Early 1990s.
For background -- and I am not an expert here -- their C++ frontend is widely known. I first heard of it because Visual C++'s Intellisense uses it, which was notable because VC does not use the msvc frontend for its own completion. I understand it's been either used or evaluated for other frontends in the past too. I worked as PM for one C++ product, and was fortunate to be able to learn a lot from our engineers; we didn't use it, but they thought highly of EDG.
It has a very strong reputation for being correct. And as such, I think open sourcing it will be a very beneficial thing for the C++ community.
There are essentially four C++ frontends: gcc, clang, MSVC, and EDG. Pretty much every C++ compiler is a reskinned version of one of those compilers. Most of the proprietary compilers have been slinking away from using EDG to using clang (e.g., Intel did this transition a few years ago).
The reason why the EDG frontend is being open-sourced is because EDG itself is closing up shop, and the open sourcing is an interim solution as EDG's customers work on migrating to using Clang instead. So... it's really not good news, because it means that one of the frontends is basically reaching end-of-life.
C++ is a sprawling language which will consume any available amount of effort or goodwill. So I don't expect you will see a "new life" for this codebase while continued effort on the "big three" compilers happens.
It has an interesting code style, the comments go _after_ the function definition but before the opening bracket.
It looks weird, but it actually makes sense! The flow is more natural - first the function definition, and then the explanation of what it does. It also avoids repeating the function name.
I write comments about what a function does and it's interface before, but comments about the implementation after. Also my pre- and post-conditions go there of course. (I'm mostly writing in C.)
One of the more unusual aspects is the naming convention for types. Most type names use the a_ prefix (e.g. a_statement_ptr), but names beginning with a vowel start with an_ instead (e.g. an_object_lifetime_ptr).
Code from that era predates the web, and a lot of open source style guides, and even most open source code itself.
So it came up in an era where folks were inventing their own style and the huge homogenizing influence of the gnu standards (and other open source projects) hadn't taken hold.
I like it. It feels like another language, and has its advantages. I really like to know of alternate ways of doing things, even if I don't adopt them myself.
Despite using C++ for a few years now, the EDG source code is still mostly C code (and in fact, the C++ code is still using the old .c file names). In particular, there's no usage of the C++ standard library.
Where other languages might use inheritance, EDG still uses the C-style `union { ... } variant;`.
On a related note, compiling EDG is extremely fast: on my machine, the EDG frontend compiles in <10s; whereas clang takes >10min (caution unfair comparison: clang includes much more than just a frontend).
I think this is fairly common practice when writing compilers. You ideally want to be able to bootstrap from other languages, and C is a much simpler starting point.
Yes, of course. It makes complete sense to have the implementation of a C++ compiler to be written in a highly portable and much simpler language like C.
It's got history! That's really unusual for moves to open-source; the dates on the earliest commits are in 1990 and they do go forward in time so that's really unusual to have that much history. I bet there's some fun stuff in there.
If I remember correctly, EDG was the only C++ implementation that actually attempted to implement the export keyword for templates in old C++. It was this implementation experience that informed the deprecation of export. EDG is a major influence in the development of C++.
Slight correction, the other compiler/front end writers more or less read the white paper and said "that is what we thought it would be like and thus why we didn't implement it".
Imagine telling your competitors not to copy some feature you have and them listening!
Prof. John Potter told me they were the only frontend that correctly implement multiple inheritance for c++98. He thought very highly of EDG... For old time c++ folks, he was a mod on comp.lang.c++.moderated and a very cool teacher. So I hope I remember his lessons correctly...
Oh, you had him as a teacher? That's awesome.
I met him and his family 25+ years ago while they were vacationing in California... and they were all great! He was also at the Morristown WG21 meeting, where C++98 was voted out (in November 1997).
(I co-moderated comp.lang.c++.moderated with John. For several years he was the person that kept it alive.)
Ah, I used EDG for static analysis, but joined when we were switching over to using Clang for the frontend. I can't say for sure, but part of it was definitely just to save money using open source. The code that was hacked on top of EDG was also ridiculous, so there was a lot of accumulated tech debt there.
Looking back at that code definitely brings back memories. As a consumer of both frontends, I will say I much preferred working with Clang's. Both needed extra work on top to support everything we needed. Maybe I'm just not as acquainted with C as I would like to be. It's cool to look at this again, though.
What's not mentioned in the announcement (at least based on a quick skim) is that EDG the company is winding down, which is likely the reason why they're open sourcing the front end.
Not really sad. They are getting older, worked for themselves doing presumably what they wanted their entire career, now they are done. They could have built the company up, instead it has been common knowledge for close to 10 years they were going to retire 'any day now.'
I'll never forget working on a personal C++ project in the very early 2000s. In parallel, I was reading Bjarne Stroustrup's famous C++ bible. He diligently explained how the “export template” feature worked. I tried to use it. I was compiling with GCC on Linux. I spent days trying to understand why it didn't work. Finally, I found a blog post explaining why it was so hard to implement, and no open source C++ compilers supported it. What a disappointment!
One interesting thing about the EDG front end is that it can emulate all the others (and in various versions of the others) and what they support, and the errors they might detect.
It isn't perfect, but it is awfully good.
Another interesting thing is that in 1999ish, when SGI open-sourced the Irix compiler (known as sgicc) into open-64, the it used a terribly hacked version of gcc as a front end to generate its internal intermediate representation.
This was because sgicc, even back then, used EDG as a front end, and EDG wasn't open and couldn't be opened up at the time.
The combination worked OK, but was pretty hacky, and I wonder if open64 would have gotten more traction than it did if it had been able to use EDG, or perhaps some other front end actually designed as a front end instead of the hacky thing.
I like this emulation feature. A frontend capable of mimicking MSVC or GCC behavior seems very useful for porting code or developing tools that need to exactly replicate the operation of another compiler.
No comment about the substance of the article but I just have to give props: this site loaded incredibly quickly for me. Like it felt like a handful of milliseconds between tapping the link on my phone and it showing up, already scrolled to the right anchor within the article. Bravo on making it snappy.
I'd say:
- A single executable can emulate pretty much all versions of MSVC, GCC, and Clang. (E.g., pass the option --gnu_version=80300 and it emulates GCC 8.3.0, including a large number of bugs/idiosynchrasies.)
- An optimized binary is pretty small.
- It builds quite quickly. (A complete "from scratch" build on a modern solid workstation will take just a few seconds.)
- It has some interesting source-to-source transformation capabilities (via cp_gen_be.c).
...
51 comments
[ 2.5 ms ] story [ 31.3 ms ] threadThe source code itself: https://github.com/edgcpp/compiler
Documentation: https://edgcpp.org/doc/
EDG was just 3 guys back then.
For background -- and I am not an expert here -- their C++ frontend is widely known. I first heard of it because Visual C++'s Intellisense uses it, which was notable because VC does not use the msvc frontend for its own completion. I understand it's been either used or evaluated for other frontends in the past too. I worked as PM for one C++ product, and was fortunate to be able to learn a lot from our engineers; we didn't use it, but they thought highly of EDG.
It has a very strong reputation for being correct. And as such, I think open sourcing it will be a very beneficial thing for the C++ community.
But also quite sad. They've announced that they are closing down.
The reason why the EDG frontend is being open-sourced is because EDG itself is closing up shop, and the open sourcing is an interim solution as EDG's customers work on migrating to using Clang instead. So... it's really not good news, because it means that one of the frontends is basically reaching end-of-life.
It looks weird, but it actually makes sense! The flow is more natural - first the function definition, and then the explanation of what it does. It also avoids repeating the function name.
void func(var1, var2) int var1, char* var2. { ... }
perhaps some legacy from that? Probably not, but just first thing that popped into my head since it feels similar :shrug:
So it came up in an era where folks were inventing their own style and the huge homogenizing influence of the gnu standards (and other open source projects) hadn't taken hold.
I like it. It feels like another language, and has its advantages. I really like to know of alternate ways of doing things, even if I don't adopt them myself.
EDIT: But in this case it seems something significant is being released, it would be better with less writing and more human if possible.
llm overused them, but llm got its training data from catchy marketing materials and youtubers
Where other languages might use inheritance, EDG still uses the C-style `union { ... } variant;`.
On a related note, compiling EDG is extremely fast: on my machine, the EDG frontend compiles in <10s; whereas clang takes >10min (caution unfair comparison: clang includes much more than just a frontend).
One of EDG developers prototyped his idea, and brought it to WG21 when it seemed reflection as originally thought for C++17 was never happening.
Imagine telling your competitors not to copy some feature you have and them listening!
Looking back at that code definitely brings back memories. As a consumer of both frontends, I will say I much preferred working with Clang's. Both needed extra work on top to support everything we needed. Maybe I'm just not as acquainted with C as I would like to be. It's cool to look at this again, though.
https://en.wikipedia.org/wiki/Edison_Design_Group ref 9: https://herbsutter.com/2025/11/10/trip-report-november-2025-...
It isn't perfect, but it is awfully good.
Another interesting thing is that in 1999ish, when SGI open-sourced the Irix compiler (known as sgicc) into open-64, the it used a terribly hacked version of gcc as a front end to generate its internal intermediate representation.
This was because sgicc, even back then, used EDG as a front end, and EDG wasn't open and couldn't be opened up at the time.
The combination worked OK, but was pretty hacky, and I wonder if open64 would have gotten more traction than it did if it had been able to use EDG, or perhaps some other front end actually designed as a front end instead of the hacky thing.
We certainly held it in high regard. It was rare that a compiler bug was in their code rather than ours :).
Something like, oh, I don't know - HTML?
I'd say: - A single executable can emulate pretty much all versions of MSVC, GCC, and Clang. (E.g., pass the option --gnu_version=80300 and it emulates GCC 8.3.0, including a large number of bugs/idiosynchrasies.) - An optimized binary is pretty small. - It builds quite quickly. (A complete "from scratch" build on a modern solid workstation will take just a few seconds.) - It has some interesting source-to-source transformation capabilities (via cp_gen_be.c). ...