5 ms·

Eighteen Years of ABI Stability

166 points by TangerineDream 2y ago

formerly_proven 2y ago
libcurl is part of the macOS API and de-facto standard on any Linux box and commonly available on BSD boxen as well. Microsoft has been shipping curl.exe for a while as well, though not the library. If Microsoft would also ship the library in %system32%, we would have a truly cross-platform and stable, OS-provided and -patched high-level network protocol client. (So that probably won't happen)
- pjmlp 2y ago
  There are more OSes out there. I never needed curl on Windows, because on OSes that provide a full stack developer experience such things are part of the platform SDK, and rich language runtimes. It is only an issue with C and C++, and their reliance on POSIX to complement the slim standard library, effectively making UNIX their "runtime" for all practical purposes.
  - fallingsquirrel 2y ago
    You missed the point. There are more OSes out there. If you had to relearn a brand new "full stack experience" for every OS just to ship a cross-platform app, you wouldn't have any time left for business logic. libcurl is great and it runs everywhere. And now for a personal opinion: I'll take libcurl over .NET's IHttpClientFactory any day.
    - pjmlp 2y ago
      I have been programming since the glory days of 8 bit home computers, try shipping cross-platform applications in Z80 and 6502, and we still had plenty of time left to do lots of stuff. Additionally, writing little wrappers around OS APIs is something that every C programmer has known since K&R C went outside UNIX V6, which again is why POSIX became a thing.
    - neonsunset 2y ago
      What? You don't need to use it explicitly most of the time. Just `new HttpClient` and cache/dispose it. Or have DI inject it for you. It will do the right thing without further input. The reason for this factory existing is pooling the underlying HttpMessageHandlers which hold an internal connection pool for efficient connection/stream(in case of HTTP2 or Quic) reuse for large applications which use DI.
- actionfromafar 2y ago
  Hm, since a DLL is a PE file and EXE is a PE file, could one load the EXE as a DLL instead? Edit, I had a recollection I saw something like that before, this might be that: https://www.codeproject.com/articles/1045674/load-exe-as-dll-mission-possible https://www.codeproject.com/articles/1045674/load-exe-as-dll...
  - Pathogen-David 2y ago
    I just checked and the curl.exe on my system does not export any symbols, so not in this case. It is possible to do that in the general sense though.
    - deleted 2y ago
      [deleted]
- hypeatei 2y ago
  > Microsoft has been shipping curl.exe for a while as well, though not the library. I'm not sure if this is accurate. Why do they include a default alias in Powershell for `curl` that points to the `Invoke-WebRequest` cmdlet then? I've always installed curl myself and removed the alias on Windows. Maybe I've never noticed the default one because of that.
  - easton 2y ago
    As of one of the later releases of Windows 10, "curl.exe" is in System32 (or somewhere else on PATH), but if you type "curl" in a powershell you get the alias. You need to type "curl.exe" to get the binary. Guessing this is for backwards compatibility with scripts written for the days when it was just PowerShell lying to you. https://curl.se/windows/microsoft.html https://curl.se/windows/microsoft.html
  - jasomill 2y ago
    curl.exe does ship with Windows. Given a Windows 11 ISO freshly downloaded from microsoft.com, we have $ 7z l /Volumes/CCCOMA_X64FRE_EN-US_DV9/sources/install.wim | egrep ' 1/Windows/Sys.*/curl.exe' 2024-09-06 00:02:14 ....A 672312 343918 1/Windows/System32/curl.exe 2024-09-06 00:02:14 ....A 585160 323710 1/Windows/SysWOW64/curl.exe This is, in fact, curl: > C:\Windows\System32\curl.exe --version curl 8.9.1 (Windows) libcurl/8.9.1 Schannel zlib/1.3 WinIDN Release-Date: 2024-07-31 Protocols: dict file ftp ftps http https imap imaps ipfs ipns mqtt pop3 pop3s smb smbs smtp smtps telnet tftp Features: alt-svc AsynchDNS HSTS HTTPS-proxy IDN IPv6 Kerberos Largefile libz NTLM SPNEGO SSL SSPI threadsafe Unicode UnixSockets My personal favorite *nix utility nobody knows ships with Windows is tar.exe, which is libarchive's bsdtar and therefore supports a wide variety of archive formats. ["1/…" is 7z syntax for the first image in the WIM file — Windows 11 Home, in this example — included here to avoid redundant output; curl.exe is included in all images. "…/SysWOW64/curl.exe" is a 32-bit curl build (32-bit Windows programs see "Windows\SysWOW64" as "Windows\System32").]
    - formerly_proven 2y ago
      > My personal favorite *nix utility nobody knows ships with Windows is tar.exe, which is libarchive's bsdtar and therefore supports a wide variety of archive formats. TIL. However, some caveats: https://github.com/libarchive/libarchive/issues/2092 https://github.com/libarchive/libarchive/issues/2092
peterkelly 2y ago
I wish developers of JavaScript frameworks had this level of commitment to stability.
- kragen 2y ago
  I agree; it's admirable. I wish the Python core developers had even the level of commitment to stability that developers of JavaScript frameworks do. Instead they intentionally break API compatibility every single release, I suppose because they assume that only worthless ideas are ever expressed in the form of Python programs.
  - JimDabell 2y ago
    I’ve been writing Python for 25 years and can’t remember projects I work on ever having compatibility broken from one version to the next (with the exception of 2 to 3, of course). Occasionally it happens to a dependency, but it always seems to be something like Cython and not actual Python code. But then, I normally try to stay on the leading edge. I think it’s more difficult if you leave it 2+ years between updates and ignore deprecation warnings. But with a year between minor releases, that leaves almost a two year window for moving off deprecated things. I think that’s reasonable. I don’t experience the pain you describe, and I don’t get the impression that the Python project treats Python programs as “worthless”. The people working on Python are Python users too, why would they make their own lives difficult?
    - kragen 2y ago
      When you bring up "ignoring deprecation warnings", you're implicitly confirming what I said, despite explicitly denying it. Perhaps this is due to a misunderstanding, so I will clarify what I was saying. Nobody has to worry about ignoring deprecation warnings in libcurl, or for that matter in C, in English, in Unicode, or in linear algebra. There's no point at which your linear algebra theorems stop working because the AMS has deprecated some postulates. Euclid's theorems still work just as well today as they did 2000 years ago. Better, in fact, because we now know of new things they apply to that Euclid couldn't have imagined. You can still read Mark Twain, Shakespeare, or even Cicero without having to "maintain" them first, though admittedly you have to be careful about interpreting them with the right version of language. That's what it means for intellectual work to have lasting value: each generation can build on the work of previous generations rather than having to redo it. Last night I watched a Primitive Technology video in which he explains why he wants to roof his new construction with fired clay tiles rather than palm-leaf thatch: in the rainy season, the leaves rot, and then the rain destroys his walls, so the construction only lasts a couple of years without maintenance. Today I opened up a program I had written in Python not 2000 years ago, not 200 years ago, not even 20 years ago, but only 11 years ago, and not touched since then. I had to fix a bunch of errors the Python maintainers intentionally introduced into my program in the 2-to-3 transition. Moreover, the "fixed" version is less correct than the version I used 11 years ago, because previously it correctly handled filename command-line arguments even if they weren't UTF-8. Now it won't, and there's evidently no way to fix it. I wish I had written it in Golang or JS. Although it wasn't the case when I started writing Python last millennium, a Python program today is a palm-leaf-thatched rainforest mud hut—intentionally so. Instead, like Euclid, I want to build my programs of something more lasting than mere masonry. I'm not claiming that you should do the same thing. A palm-leaf-thatched roof is easier to build and useful for many purposes. But it is no substitute for something more lasting. Today's Python is fine for keeping a service running as long as you have a staff of Python programmers. As a medium of expression of ideas, however, it's like writing in the sand at low tide.
tialaramex 2y ago
Because this library is so very widely used, in practice it is subject to Hyrum's law ABI breaks far beyond what is characterised in the SO_NAME. At the extreme Hyrum's law gets you "spacebar heating", this is not a demand that somehow nothing must change, but an acknowledgement of our reality. Basically even though Daniel might say "I didn't change the ABI" if your code worked before and now it didn't, as far as you're concerned that's an ABI break. This particularly shows up for changed defaults and for removing stuff that's "unused" except that you relied on it and so now your code doesn't work. Daniel brings up NPN because that seems easy for the public Internet but there have been other examples where a default changed and well... too bad, you were relying on something and now it's changed, but you should have just known to set what you wanted and then you'd have been fine.
Semaphor 2y ago
> “third party” transfers over FTP, Ohh that takes me back, that feature was used heavily in the FXP warez scene (the one the proper warez people looked down on), you’d find vulnerable FTP servers to gain access to, and the best ones would support this. That way you could quickly spread releases over multiple mirrors without being slowed down by your home internet.
- throw_a_grenade 2y ago
  Those were fun times, but torrent fits this use case now. You seed the chunk a single time and it magically gets distributed, like you said, without being slowed down by your home internet... That's progress I believe.
nuancebydefault 2y ago
I'm a bit confused with the usage of ABI here. I thought compatibility between apps and libs is on the API level, while the ABI sits between machine (cpu intructions) and low level (curl?) lib?
- throw_a_grenade 2y ago
  Nope, API compatibility is when you write the code, and ABI compatibility is what happens to already compiled code, but still between app and library. Say you compiled your app against libcurl.so.4 file taken from curl 7.88 packaged by Debian. What happens when, far in the future, you will move your executable file, without recompiling, to a system which has curl 12345.67, but the file will still be libcurl.so.4? It should work fine, that is, the library should export the same symbols (maybe some more added), with more or less the same functionality. Possibly implemented differently, maybe accepting more flags, but the stuff that is there, will be there. To parent's downvoters: would you kindly cut him some slack? It's OK to ask if you don't know. https://xkcd.com/1053/ https://xkcd.com/1053/
  - DanielHB 2y ago
    Just for a small example how both are not the same, in your C library if you move the positions of a field in a struct it can actually break ABI compatibility (meaning you need to recompile your software), but not API compatibility (meaning you don't need to update your code).
    - thrtythreeforty 2y ago
      And the opposite is true too: you can break API (by renaming a field) while preserving the ABI (since it didn't move/change type).
      - NekkoDroid 2y ago
        You can also with certain type of APIs increase the size of structs and still be ABI compatible. This is usually done by encoding the size of the type as a member of the struct that is usually assigned via `x.size = sizeof(x)` and passed around as pointers. Takes real care to maintain that though. IIRC this appears somewhat frequently in Win32.
ForHackernews 2y ago
> Before this release, you could use curl to do “third party” transfers over FTP, and in this release you could no longer do that. That is a feature when the client (curl) connects to server A and instructs that server to communicate with server B and do file transfers among themselves, without sending data to and from the client. That sounds like a super useful feature that would be great if more FTP servers supported it. I guess FTP itself is a dying protocol these days, but it's extremely simple and does what it says on the tin.
- crabbone 2y ago
  FTP is still the best way to transfer files between a phone and a PC. Well, Android anyways. I don't know how things work in the Apple world. It's bizarre that whatever the "official" method of file transfer is is so bad. Also, managing files on Android is, on its own very bad. FTP allows connecting a decent file manager to the phone and do the management externally.
- raxxorraxor 2y ago
  Sadly FTP didn't seem to have a smooth TLS transition. There is FTPS (among SFTP), but I have rarely seen it in use. I think it will survive as a protocol as a fallback mechanism. Ironically I used FTP on a smartphone here and there because Smartphone OS are abysmally useless. Don't get me started with your awesome proprietary sync app, I don't do trashy and they all are. Otherwise I do everything today through scp and http, but it is less optimal technically. It just happens to be widely available. FTP theoretically would provide a cleaner way for transfers and permission management.
exabrial 2y ago
There’s JavaScript code we have that won’t compile after 3 months. Pretty sad state of affairs these days.
- robviren 2y ago
  Compile is rather generous. The massive teetering dependency tree certainly is prone to breaking, but I am not certain I can draw much parallel between the API stability of JS vs the ABI stability of libcurl. If anything, I can still properly render some pretty dang old websites just fine and, for the most part, the websites will work just fine. Mainly benefitted by the light use of JavaScript using probably no external dependent libraries. Though your milage will vary depending on if you go back to browser specific APIs when all that browser war nonsense was going on. I love to bash on JS as much as the next guy, but a large portion of the blame is actually the modern use of it, not an inherent quality of the language breaking compatibility over time.
- mrguyorama 2y ago
  How? We have an ancient (in javascript years) app that webpacks stupid template systems and polyfills and all sorts of cruft that should have never been in the first place and we haven't had to touch any of that in years. What dependency or feature forces you to chase versions?
blenderob 2y ago
What are some things you could do in a C project to cause ABI breakage? I ask this because I'd like to know what practices I might want to avoid to guarantee that there is no ABI breakage in my C project.
- CJefferson 2y ago
  One big thing to watch out for is structs. You can’t add extra members later. If you have a struct which might grow, don’t actually make it part of the ABI, don’t give users any way to find it’s size, and write functions to create, destroy and query it.
  - blenderob 2y ago
    > If you have a struct which might grow, don’t actually make it part of the ABI, don’t give users any way to find it’s size, and write functions to create, destroy and query it. Thanks! This is very insightful. What is a solution to this? If I cannot expose structs that might grow what do I expose then? Or is the solution something like I can expose the structs that I need to expose but if I need to ever extend them in future, then I create a new struct for it?
    - GolDDranks 2y ago
      You shall expose the structs as anonymous types behind a pointer, and expose functions that act on that pointer.
    - acuozzo 2y ago
      > What is a solution to this? If I cannot expose structs that might grow what do I expose then? Option 1: If allocating from the heap or somewhere otherwise fixed in place, then return a pointer-to-void (void *) and cast back to pointer-to-your-struct when the user gives it back to you. Option 2: If allocating from a pool, just return the index.
      - tialaramex 2y ago
jedisct1 2y ago
Take note, Rust.
- tialaramex 2y ago
  Rust has explicit provision for C-style ABI if you want that and are willing to pay for it. The provision could be improved, and valuable work on that has taken place and is ongoing, but I think the harsh lesson in this space isn't for Rust but for C++ which fell into just delivering absolute ABI freeze years ago out of terrorized panic rather than any coherent policy or strategy. Plenty of people told WG21 (the C++ committee) that they need to fix this, P1863R0 ("ABI: Now or Never") is five years old on Friday. If you bet "Never" when that paper was written, you're ahead by five years, if you understand how this actually works you know that you have much longer. When Titus wrote that he estimated 5-10% perf left on the table. That's a thin margin, on its own it would not justify somebody to come in and pick that up. But it isn't on its own, there are a long list of problems with C++.
amadio 2y ago
Unfortunately this is no longer maintained, but it's interesting nonetheless: https://abi-laboratory.pro/?view=timeline&l=curl https://abi-laboratory.pro/?view=timeline&l=curl
anotherhue 2y ago
> The Debian project even decided to override our decision “no, that is not an ABI breakage” and added a local patch in their build that lowered the SONAME number back to 3 again in their builds. A patch they would stick to for many years to come. I get mad even reading about this. If I was in his shoes I'd demand they fork and rename their implementation. Too many times we hear about over zealous debian patches being the source is issues.

libcurl is part of the macOS API and de-facto standard on any Linux box and commonly available on BSD boxen as well. Microsoft has been shipping curl.exe for a while as well, though not the library. If Microsoft would also ship the library in %system32%, we would have a truly cross-platform and stable, OS-provided and -patched high-level network protocol client. (So that probably won't happen)

pjmlp 2y ago
There are more OSes out there. I never needed curl on Windows, because on OSes that provide a full stack developer experience such things are part of the platform SDK, and rich language runtimes. It is only an issue with C and C++, and their reliance on POSIX to complement the slim standard library, effectively making UNIX their "runtime" for all practical purposes.
- fallingsquirrel 2y ago
  You missed the point. There are more OSes out there. If you had to relearn a brand new "full stack experience" for every OS just to ship a cross-platform app, you wouldn't have any time left for business logic. libcurl is great and it runs everywhere. And now for a personal opinion: I'll take libcurl over .NET's IHttpClientFactory any day.
  - pjmlp 2y ago
    I have been programming since the glory days of 8 bit home computers, try shipping cross-platform applications in Z80 and 6502, and we still had plenty of time left to do lots of stuff. Additionally, writing little wrappers around OS APIs is something that every C programmer has known since K&R C went outside UNIX V6, which again is why POSIX became a thing.
  - neonsunset 2y ago
    What? You don't need to use it explicitly most of the time. Just `new HttpClient` and cache/dispose it. Or have DI inject it for you. It will do the right thing without further input. The reason for this factory existing is pooling the underlying HttpMessageHandlers which hold an internal connection pool for efficient connection/stream(in case of HTTP2 or Quic) reuse for large applications which use DI.
actionfromafar 2y ago
Hm, since a DLL is a PE file and EXE is a PE file, could one load the EXE as a DLL instead? Edit, I had a recollection I saw something like that before, this might be that: https://www.codeproject.com/articles/1045674/load-exe-as-dll-mission-possible https://www.codeproject.com/articles/1045674/load-exe-as-dll...
- Pathogen-David 2y ago
  I just checked and the curl.exe on my system does not export any symbols, so not in this case. It is possible to do that in the general sense though.
  - deleted 2y ago
    [deleted]
hypeatei 2y ago
> Microsoft has been shipping curl.exe for a while as well, though not the library. I'm not sure if this is accurate. Why do they include a default alias in Powershell for `curl` that points to the `Invoke-WebRequest` cmdlet then? I've always installed curl myself and removed the alias on Windows. Maybe I've never noticed the default one because of that.
- easton 2y ago
  As of one of the later releases of Windows 10, "curl.exe" is in System32 (or somewhere else on PATH), but if you type "curl" in a powershell you get the alias. You need to type "curl.exe" to get the binary. Guessing this is for backwards compatibility with scripts written for the days when it was just PowerShell lying to you. https://curl.se/windows/microsoft.html https://curl.se/windows/microsoft.html
- jasomill 2y ago
  curl.exe does ship with Windows. Given a Windows 11 ISO freshly downloaded from microsoft.com, we have $ 7z l /Volumes/CCCOMA_X64FRE_EN-US_DV9/sources/install.wim | egrep ' 1/Windows/Sys.*/curl.exe' 2024-09-06 00:02:14 ....A 672312 343918 1/Windows/System32/curl.exe 2024-09-06 00:02:14 ....A 585160 323710 1/Windows/SysWOW64/curl.exe This is, in fact, curl: > C:\Windows\System32\curl.exe --version curl 8.9.1 (Windows) libcurl/8.9.1 Schannel zlib/1.3 WinIDN Release-Date: 2024-07-31 Protocols: dict file ftp ftps http https imap imaps ipfs ipns mqtt pop3 pop3s smb smbs smtp smtps telnet tftp Features: alt-svc AsynchDNS HSTS HTTPS-proxy IDN IPv6 Kerberos Largefile libz NTLM SPNEGO SSL SSPI threadsafe Unicode UnixSockets My personal favorite *nix utility nobody knows ships with Windows is tar.exe, which is libarchive's bsdtar and therefore supports a wide variety of archive formats. ["1/…" is 7z syntax for the first image in the WIM file — Windows 11 Home, in this example — included here to avoid redundant output; curl.exe is included in all images. "…/SysWOW64/curl.exe" is a 32-bit curl build (32-bit Windows programs see "Windows\SysWOW64" as "Windows\System32").]
  - formerly_proven 2y ago
    > My personal favorite *nix utility nobody knows ships with Windows is tar.exe, which is libarchive's bsdtar and therefore supports a wide variety of archive formats. TIL. However, some caveats: https://github.com/libarchive/libarchive/issues/2092 https://github.com/libarchive/libarchive/issues/2092

peterkelly 2y ago

I wish developers of JavaScript frameworks had this level of commitment to stability.

kragen 2y ago
I agree; it's admirable. I wish the Python core developers had even the level of commitment to stability that developers of JavaScript frameworks do. Instead they intentionally break API compatibility every single release, I suppose because they assume that only worthless ideas are ever expressed in the form of Python programs.
- JimDabell 2y ago
  I’ve been writing Python for 25 years and can’t remember projects I work on ever having compatibility broken from one version to the next (with the exception of 2 to 3, of course). Occasionally it happens to a dependency, but it always seems to be something like Cython and not actual Python code. But then, I normally try to stay on the leading edge. I think it’s more difficult if you leave it 2+ years between updates and ignore deprecation warnings. But with a year between minor releases, that leaves almost a two year window for moving off deprecated things. I think that’s reasonable. I don’t experience the pain you describe, and I don’t get the impression that the Python project treats Python programs as “worthless”. The people working on Python are Python users too, why would they make their own lives difficult?
  - kragen 2y ago
    When you bring up "ignoring deprecation warnings", you're implicitly confirming what I said, despite explicitly denying it. Perhaps this is due to a misunderstanding, so I will clarify what I was saying. Nobody has to worry about ignoring deprecation warnings in libcurl, or for that matter in C, in English, in Unicode, or in linear algebra. There's no point at which your linear algebra theorems stop working because the AMS has deprecated some postulates. Euclid's theorems still work just as well today as they did 2000 years ago. Better, in fact, because we now know of new things they apply to that Euclid couldn't have imagined. You can still read Mark Twain, Shakespeare, or even Cicero without having to "maintain" them first, though admittedly you have to be careful about interpreting them with the right version of language. That's what it means for intellectual work to have lasting value: each generation can build on the work of previous generations rather than having to redo it. Last night I watched a Primitive Technology video in which he explains why he wants to roof his new construction with fired clay tiles rather than palm-leaf thatch: in the rainy season, the leaves rot, and then the rain destroys his walls, so the construction only lasts a couple of years without maintenance. Today I opened up a program I had written in Python not 2000 years ago, not 200 years ago, not even 20 years ago, but only 11 years ago, and not touched since then. I had to fix a bunch of errors the Python maintainers intentionally introduced into my program in the 2-to-3 transition. Moreover, the "fixed" version is less correct than the version I used 11 years ago, because previously it correctly handled filename command-line arguments even if they weren't UTF-8. Now it won't, and there's evidently no way to fix it. I wish I had written it in Golang or JS. Although it wasn't the case when I started writing Python last millennium, a Python program today is a palm-leaf-thatched rainforest mud hut—intentionally so. Instead, like Euclid, I want to build my programs of something more lasting than mere masonry. I'm not claiming that you should do the same thing. A palm-leaf-thatched roof is easier to build and useful for many purposes. But it is no substitute for something more lasting. Today's Python is fine for keeping a service running as long as you have a staff of Python programmers. As a medium of expression of ideas, however, it's like writing in the sand at low tide.

tialaramex 2y ago

Because this library is so very widely used, in practice it is subject to Hyrum's law ABI breaks far beyond what is characterised in the SO_NAME. At the extreme Hyrum's law gets you "spacebar heating", this is not a demand that somehow nothing must change, but an acknowledgement of our reality. Basically even though Daniel might say "I didn't change the ABI" if your code worked before and now it didn't, as far as you're concerned that's an ABI break. This particularly shows up for changed defaults and for removing stuff that's "unused" except that you relied on it and so now your code doesn't work. Daniel brings up NPN because that seems easy for the public Internet but there have been other examples where a default changed and well... too bad, you were relying on something and now it's changed, but you should have just known to set what you wanted and then you'd have been fine.

Semaphor 2y ago

> “third party” transfers over FTP, Ohh that takes me back, that feature was used heavily in the FXP warez scene (the one the proper warez people looked down on), you’d find vulnerable FTP servers to gain access to, and the best ones would support this. That way you could quickly spread releases over multiple mirrors without being slowed down by your home internet.

throw_a_grenade 2y ago
Those were fun times, but torrent fits this use case now. You seed the chunk a single time and it magically gets distributed, like you said, without being slowed down by your home internet... That's progress I believe.

nuancebydefault 2y ago

I'm a bit confused with the usage of ABI here. I thought compatibility between apps and libs is on the API level, while the ABI sits between machine (cpu intructions) and low level (curl?) lib?

throw_a_grenade 2y ago
Nope, API compatibility is when you write the code, and ABI compatibility is what happens to already compiled code, but still between app and library. Say you compiled your app against libcurl.so.4 file taken from curl 7.88 packaged by Debian. What happens when, far in the future, you will move your executable file, without recompiling, to a system which has curl 12345.67, but the file will still be libcurl.so.4? It should work fine, that is, the library should export the same symbols (maybe some more added), with more or less the same functionality. Possibly implemented differently, maybe accepting more flags, but the stuff that is there, will be there. To parent's downvoters: would you kindly cut him some slack? It's OK to ask if you don't know. https://xkcd.com/1053/ https://xkcd.com/1053/
- DanielHB 2y ago
  Just for a small example how both are not the same, in your C library if you move the positions of a field in a struct it can actually break ABI compatibility (meaning you need to recompile your software), but not API compatibility (meaning you don't need to update your code).
  - thrtythreeforty 2y ago
    And the opposite is true too: you can break API (by renaming a field) while preserving the ABI (since it didn't move/change type).
    - NekkoDroid 2y ago
      You can also with certain type of APIs increase the size of structs and still be ABI compatible. This is usually done by encoding the size of the type as a member of the struct that is usually assigned via `x.size = sizeof(x)` and passed around as pointers. Takes real care to maintain that though. IIRC this appears somewhat frequently in Win32.

ForHackernews 2y ago

> Before this release, you could use curl to do “third party” transfers over FTP, and in this release you could no longer do that. That is a feature when the client (curl) connects to server A and instructs that server to communicate with server B and do file transfers among themselves, without sending data to and from the client. That sounds like a super useful feature that would be great if more FTP servers supported it. I guess FTP itself is a dying protocol these days, but it's extremely simple and does what it says on the tin.

crabbone 2y ago
FTP is still the best way to transfer files between a phone and a PC. Well, Android anyways. I don't know how things work in the Apple world. It's bizarre that whatever the "official" method of file transfer is is so bad. Also, managing files on Android is, on its own very bad. FTP allows connecting a decent file manager to the phone and do the management externally.
raxxorraxor 2y ago
Sadly FTP didn't seem to have a smooth TLS transition. There is FTPS (among SFTP), but I have rarely seen it in use. I think it will survive as a protocol as a fallback mechanism. Ironically I used FTP on a smartphone here and there because Smartphone OS are abysmally useless. Don't get me started with your awesome proprietary sync app, I don't do trashy and they all are. Otherwise I do everything today through scp and http, but it is less optimal technically. It just happens to be widely available. FTP theoretically would provide a cleaner way for transfers and permission management.

exabrial 2y ago

There’s JavaScript code we have that won’t compile after 3 months. Pretty sad state of affairs these days.

robviren 2y ago
Compile is rather generous. The massive teetering dependency tree certainly is prone to breaking, but I am not certain I can draw much parallel between the API stability of JS vs the ABI stability of libcurl. If anything, I can still properly render some pretty dang old websites just fine and, for the most part, the websites will work just fine. Mainly benefitted by the light use of JavaScript using probably no external dependent libraries. Though your milage will vary depending on if you go back to browser specific APIs when all that browser war nonsense was going on. I love to bash on JS as much as the next guy, but a large portion of the blame is actually the modern use of it, not an inherent quality of the language breaking compatibility over time.
mrguyorama 2y ago
How? We have an ancient (in javascript years) app that webpacks stupid template systems and polyfills and all sorts of cruft that should have never been in the first place and we haven't had to touch any of that in years. What dependency or feature forces you to chase versions?

blenderob 2y ago

What are some things you could do in a C project to cause ABI breakage? I ask this because I'd like to know what practices I might want to avoid to guarantee that there is no ABI breakage in my C project.

CJefferson 2y ago
One big thing to watch out for is structs. You can’t add extra members later. If you have a struct which might grow, don’t actually make it part of the ABI, don’t give users any way to find it’s size, and write functions to create, destroy and query it.
- blenderob 2y ago
  > If you have a struct which might grow, don’t actually make it part of the ABI, don’t give users any way to find it’s size, and write functions to create, destroy and query it. Thanks! This is very insightful. What is a solution to this? If I cannot expose structs that might grow what do I expose then? Or is the solution something like I can expose the structs that I need to expose but if I need to ever extend them in future, then I create a new struct for it?
  - GolDDranks 2y ago
    You shall expose the structs as anonymous types behind a pointer, and expose functions that act on that pointer.
  - acuozzo 2y ago
    > What is a solution to this? If I cannot expose structs that might grow what do I expose then? Option 1: If allocating from the heap or somewhere otherwise fixed in place, then return a pointer-to-void (void *) and cast back to pointer-to-your-struct when the user gives it back to you. Option 2: If allocating from a pool, just return the index.
    - tialaramex 2y ago

jedisct1 2y ago

Take note, Rust.

tialaramex 2y ago
Rust has explicit provision for C-style ABI if you want that and are willing to pay for it. The provision could be improved, and valuable work on that has taken place and is ongoing, but I think the harsh lesson in this space isn't for Rust but for C++ which fell into just delivering absolute ABI freeze years ago out of terrorized panic rather than any coherent policy or strategy. Plenty of people told WG21 (the C++ committee) that they need to fix this, P1863R0 ("ABI: Now or Never") is five years old on Friday. If you bet "Never" when that paper was written, you're ahead by five years, if you understand how this actually works you know that you have much longer. When Titus wrote that he estimated 5-10% perf left on the table. That's a thin margin, on its own it would not justify somebody to come in and pick that up. But it isn't on its own, there are a long list of problems with C++.

amadio 2y ago

Unfortunately this is no longer maintained, but it's interesting nonetheless: https://abi-laboratory.pro/?view=timeline&l=curl https://abi-laboratory.pro/?view=timeline&l=curl

anotherhue 2y ago

> The Debian project even decided to override our decision “no, that is not an ABI breakage” and added a local patch in their build that lowered the SONAME number back to 3 again in their builds. A patch they would stick to for many years to come. I get mad even reading about this. If I was in his shoes I'd demand they fork and rename their implementation. Too many times we hear about over zealous debian patches being the source is issues.