The other issue is that people seem to just copy configure/autotools scripts over from older or other projects because either they are lazy or don't understand them enough to do it themselves. The result is that even with relatively modern code bases that only target something like x86, arm and maybe mips and only gcc/clang, you still get checks for the size of an int, or which header is needed for printf, or whether long long exists.... And then the entire code base never checks the generated macros in a single place, uses int64_t and never checks for stint.h in the configure script...
I don't think it's fair to say "because they are lazy or don't understand". Who would want to understand that mess? It isn't a virtue.
A fairer criticism would be that they have no sense to use a more sane build system. CMake is a mess but even that is faaaaar saner than autotools, and probably more popular at this point.
I took the trouble (and even spent the money) to get to grips with autotools in a structured and detailed way by buying a book [1] about it and reading as much as possible. Yes, it's not trivial, but autotools are not witchcraft either, but as written elsewhere, a masterpiece of engineering. I have dealt with it without prejudice and since then I have been more of a fan of autotools than a hater. Anyway, I highly recommend the book and yes, after reading it, I think autotools is better than its reputation.
Autotools use M4 to meta-program a bash script that meta-programs a bunch of C(++) sources and generates C(++) sources that utilizes meta-programming for different configurations; after which the meta-programmed script, again, meta-programs monolithic makefiles.
autotools is the worst, except for all the others.
I'd like to think of myself as reasonable, so I'll just say that reasonable people may disagree with your assertion that cmake is in any way at all better than autotools.
Configure-make is easier to use for someone else. Configuring a cmake based project is slightly harder. In every other conceivable way I agree 100% (until someone can convince me otherwise)
Correct. I avoid autotools and cmake as much as I can. I'd better write Makefiles by hand. But when I need to deal with them, I'd prefer cmake. I can can modify CMakeLists.txt in a meaningful way and get the results I want. I wouldn't touch autotools build system because I never was able to figure out which of the files is the configuration that is meant to be edited by hands and not generated by scripts in other files. I tried to dig the documentation but I never made it.
Simple projects: just use plain C. This is dwm, the window manager that spawned a thousand forks. No ./configure in sight: <https://git.suckless.org/dwm/files.html>
If you run into platform-specific stuff, just write a ./configure in simple and plain shell: <https://git.suckless.org/utmp/file/configure.html>. Even if you keep adding more stuff, it shouldn't take more than 100ms.
If you're doing something really complex (like say, writing a compiler), take the approach from Plan 9 / Go. Make a conditionally included header file that takes care of platform differences for you. Check the $GOARCH/u.h files here:
Interesting that you would bring up Go. Go is probably the most head-desk language of all for writing portable code. Go will fight you the whole way.
Even plain C is easier.
You can have a whole file be for OpenBSD, to work around that some standard library parts have different types on different platforms.
So now you need one file for all platforms and architectures where Timeval.Usec is int32, and another file for where it is int64. And you need to enumerate in your code all GOOS/GOARCH combinations that Go supports or will ever support.
You need a file for Linux 32 bit ARM (int32/int32 bit), one for Linux 64 bit ARM (int64,int64), one for OpenBSD 32 bit ARM (int64/int32), etc…. Maybe you can group them, but this is just one difference, so in the end you'll have to do one file per combination of OS and Arch. And all you wanted was pluggable "what's a Timeval?". Something that all build systems solved a long time ago.
And then maybe the next release of OpenBSD they've changed it, so now you cannot use Go's way to write portable code at all.
So between autotools, cmake, and the Go method, the Go method is by far the worst option for writing portable code.
I have specifically given an example of u.h defining types such as i32, u64, etc to avoid running a hundred silly tests like "how long is long", "how long is long long", etc.
> So now you need one file for all platforms and architectures where Timeval.Usec is int32, and another file for where it is int64. And you need to enumerate in your code all GOOS/GOARCH combinations that Go supports or will ever support.
I assume you mean [syscall.Timeval]?
$ go doc syscall
[...]
Package syscall contains an interface to the low-level operating system
primitives. The details vary depending on the underlying system [...].
Do you have a specific use case for [syscall], where you cannot use [time]?
It’s always wise to be specific about the sizes you want for your variables. You don’t want your ancient 64-bit code to act differently on your grandkids 128-bit laptops. Unless, of course, you want to let the compiler decide whether to leverage higher precision types that become available after you retire.
I did something like the system described in this article a few years back. [1]
Instead of splitting the "configure" and "make" steps though, I chose to instead fold much of the "configure" step into the "make".
To clarify, this article describes a system where `./configure` runs a bunch of compilations in parallel, then `make` does stuff depending on those compilations.
If one is willing to restrict what the configure can detect/do to writing to header files (rather than affecting variables examined/used in a Makefile), then instead one can have `./configure` generate a `Makefile` (or in my case, a ninja file), and then have the "run the compiler to see what defines to set" and "run compiler to build the executable" can be run in a single `make` or `ninja` invocation.
The simple way here results in _almost_ the same behavior: all the "configure"-like stuff running and then all the "build" stuff running. But if one is a bit more careful/clever and doesn't depend on the entire "config.h" for every "<real source>.c" compilation, then one can start to interleave the work perceived as "configuration" with that seen as "build". (I did not get that fancy)
The problem is that the various `__has_foo` aren't actually reliable in practice - they don't tell you if the attribute, builtin, include, etc. actually works the way it's supposed to without bugs, or if it includes a particular feature (accepts a new optional argument, or allows new values for an existing argument, etc.).
You should use double underscores on attribute names to avoid conflicts with macros (user-defined macros beginning with double underscores are forbidden, as identifiers beginning with double underscores are reserved).
#if __has_attribute(__cold__)
# warning "This works too"
#endif
static void __attribute__((__cold__))
foo(void)
{
// This works too
}
yep. C's really come a long way with the special operators for checking if attributes exist, if builtins exist, if headers exist, etc.
Covers a very large part of what is needed, making fewer and fewer things need to end up in configure scripts. I think most of what's left is checking for items (types, functions) existence and their shape, as you were doing :). I can dream about getting a nice special operator to check for fields/functions, would let us remove even more from configure time, but I suspect we won't because that requires type resolution and none of the existing special operators do that.
You still need a configure step for the "where are my deps" part of it, though both autotools and CMake would be way faster if all they were doing was finding, and not any testing.
Noticed an easter egg in this article. The text below "I'm sorry, but in the year 2025, this is ridiculous:" is animated entirely without Javascript or .gif files. It's pure CSS.
It's a bit of a balance once you get bigger dependencies. A generic autoconf is annoying to write, but rarely an issue when packaging for a distro. Most issues I've had to fix in nixpkgs were for custom builds unfortunately.
But if you don't plan to distribute things widely (or have no deps).. Whatever, just do what works for you.
Write your own configure? For an internal project, where much is under domain control, sure. But for the 1000s of projects trying to multi-plarform and/or support flavours/versions - oh gosh.
It depends on how much platform specific stuff you are trying to use. Also in 2025 most packages are tailored for the operating system by packagers - not the original authors.
Autotools is going to check every config from the past 50 years.
autoconf is in no way, shape or form an "official" build system associated with C. It is a GNU creation and certainly popular, but not to a "monopoly" degree, and it's share is declining. (plain make & meson & cmake being popular alternatives)
It can build a Rust program (build.rs) which builds things that aren't Rust, but that's an entirely different use case (building non-Rust library to use inside of Rust programs).
There's GprBuild (Ada tool) that can build C (not sure about C++). It also has more elaborate configuration structure, but I didn't use it extensively to tell what exactly and how exactly does it do it. In combination with Alire it can also manage dependencies Cargo-style.
And on macOS, the notarization checks for all the conftest binaries generated by configure add even more latency. Apple reneged on their former promise to give an opt-out for this.
Man, I've spent way too many hours wrestling with build systems like autotools and cmake and they both make me want to just toss my laptop sometimes - feels like it's way harder than it needs to be each time. You ever think we'll actually get to a point where building stuff just works, no endless config scripts or chasing weird cross-platform bugs?
Agreed! The CMake Xcode generator is extremely slow because not only is it running the configure tests sequentially, but it generates a new Xcode project for each of them.
Very nice! I always get annoyed when my fancy 16 thread CPU is left barely used as one thread is burning away with the rest sitting and waiting. Bookmarking this for later to play around with whatever projects I use that still use configure.
Also, I was surprised when the animated text at the top of the article wasn't a gif, but actual text. So cool!
I get the impression configure not only runs sequentially, but incrementally, where previous results can change the results of tests run later. Were it just sequential, running multiple tests as separate processes would be relatively simple.
Also, you shouldn’t need to run ./configure every time you run make.
No, but if you are doing something like rebuilding a distro's worth of packages from source from scratch, the configure step starts to dominate. I build around 550, and it takes around 6 hours on a single node.
Most checks are common, so what can help is having a shared cache for all configure scripts so if you have 400 packages to rebuild, it doesn't check 400 times if you should use flock or fcntl. This approach is described here:
https://jmmv.dev/2022/06/autoconf-caching.html
It doesn't help that autoconf is basically abandonware, with one forlorn maintainer trying to resuscitate it, but creating major regressions with new releases:
https://lwn.net/Articles/834682/
On the topic* of having 24 cores and wanting to put them to work: when I were a lad the promise was that pure functional programming would trivially allow for parallel execution of functions. Has this future ever materialized in a modern language / runtime?
x = 2 + 2
y = 2 * 2
z = f(x, y)
print(z)
…where x and y evaluate in parallel without me having to do anything. Clojure, perhaps?
*And superficially off the topic of this thread, but possibly not.
Superscalar processors (which include all mainstream ones these days) do this within a single core, provided there are no data dependencies between the assignment statements. They have multiple arithmetic logic units, and they can start a second operation while the first is executing.
But yeah, I agree that we were promised a lot more automatic multithreading than we got. History has proven that we should be wary of any promises that depend on a Sufficiently Smart Compiler.
Eh, in this case not splitting them up to compute them in parallel is the smartest thing to do. Locking overhead alone is going to dwarf every other cost involved in that computation.
Yeah, I think the dream was more like, “The compiler looks at a map or filter operation and figures out whether it’s worth the overhead to parallelize it automatically.” And that turns out to be pretty hard, with potentially painful (and nondeterministic!) consequences for failure.
Maybe it would have been easier if CPU performance didn’t end up outstripping memory performance so much, or if cache coherency between cores weren’t so difficult.
Spawning threads or using a thread pool implicitly would be pretty bad - it would be difficult to reason about performance if the compiler was to make these choices for you.
I think it has shaken out the way it has, is because compile time optimizations to this extent require knowing runtime constraints/data at compile time. Which for non-trivial situations is impossible, as the code will be run with too many different types of input data, with too many different cache sizes, etc.
The CPU has better visibility into the actual runtime situation, so can do runtime optimization better.
In some ways, it’s like a bytecode/JVM type situation.
If we can write code to dispatch different code paths (like has been used for decades for SSE, later AVX support within one binary), then we can write code to parallelize large array execution based on heuristics. Not much different from busy spins falling back to sleep/other mechanisms when the fast path fails after ca. 100-1000 attempts to secure a lock.
For the trivial example of 2+2 like above, of course, this is a moot discussion. The commenter should've lead with a better example.
I think you’re fixating on the very specific example. Imagine if instead of 2 + 2 it was multiplying arrays of large matrices. The compiler or runtime would be smart enough to figure out if it’s worth dispatching the parallelism or not for you. Basically auto vectorisation but for parallelism
I mean, theoretically it's possible. A super basic example would be if the data is known at compile time, it could be auto-parallelized, e.g.
int buf_size = 10000000;
auto vec = make_large_array(buf_size);
for (const auto& val : vec)
{
do_expensive_thing(val);
}
this could clearly be parallelised. In a C++ world that doesn't exist, we can see that it's valid.
If I replace it with
int buf_size = 10000000;
cin >> buf_size;
auto vec = make_large_array(buf_size);
for (const auto& val : vec)
{
do_expensive_thing(val);
}
the compiler could generate some code that looks like:
if buf_size >= SOME_LARGE_THRESHOLD {
DO_IN_PARALLEL
} else {
DO_SERIAL
}
With some background logic for managing threads, etc. In a C++-style world where "control" is important it likely wouldn't fly, but if this was python...
arr_size = 10000000
buf = [None] * arr_size
for x in buf:
do_expensive_thing(x)
That looks more like a SIMD problem than a multi-core problem
You want bigger units of work for multiple cores, otherwise the coordination overhead will outweigh the work the application is doing
I think the Erlang runtime is probably the best use of functional programming and multiple cores. Since Erlang processes are shared nothing, I think they will scale to 64 or 128 cores just fine
Whereas the GC will be a bottleneck in most languages with shared memory ... you will stop scaling before using all your cores
But I don't think Erlang is as fine-grained as your example ...
AFAIU Erlang is not that fast an interpreter; I thought the Pony Language was doing something similar (shared nothing?) with compiled code, but I haven't heard about it in awhile
There's some sharing used to avoid heavy copies, though GC runs at the process level. The implementation is tilted towards copying between isolated heaps over sharing, but it's also had performance work done over the years. (In fact, if I really want to cause a global GC pause bottleneck in Erlang, I can abuse persistent_term to do this.)
> …where x and y evaluate in parallel without me having to do anything.
I understand that yours is a very simple example, but a) such things are already parallelized even on a single thread thanks to all the internal CPU parallelism, b) one should always be mindful of Amdahl's law, c) truly parallel solutions to various problems tend to be structurally different from serial ones in unpredictable ways, so there's no single transformation, not even a single family of transformations.
Bend[1] and Vine[1] are two experimental programming languages that take similar approaches to automatically parallelizing programs; interaction nets[3]. IIUC, they basically turn the whole program into one big dependency graph, then the runtime figures out what can run in parallel and distributes the work to however many threads you can throw at it. It's also my understanding that they are currently both quite slow, which makes sense as the focus has been on making `write embarrassingly parallelizable program -> get highly parallelized execution` work at all until recently. Time will tell if they can manage enough optimizations that the approach enables you to get reasonably performing parallel functional programs 'for free'.
There have been experimental parallel graph reduction machines. Excel has a parallel evaluator these days.
Oddly enough, functional programming seems to be a poor fit for this because the fanout tends to be fairly low: individual operations have few inputs, and single-linked lists and trees are more common than arrays.
I believe it's not the language preventing it but the nature of parallel computing. The overhead of splitting up things and then reuniting them again is high enough to make trivial cases not worth it. OTOH we now have pretty good compiler autovectorization which does a lot of parallel magic if you set things right. But it's not handled at the language level either.
there have been fortran compilers which have done auto parallelization for decades, i think nvidia released a compiler that will take your code and do its best to run it on a gpu
this works best for scientific computing things that run through very big loops where there is very little interaction between iterations
Why do we need to even run most of the things in ./configure? Why not just have a file in /etc which is updated when you install various packages which ./configure can read to learn various stats about the environment? Obviously it will still allow setting various things with parameters and create a Makefile, but much faster.
Keep in mind that the build intentionally depends on environment variables, people often install non-packaged dependencies in bad ways, and cross-compiling is a thing, so it's not that simple.
(The conclusion I distilled out of reading that at the time, I think, was that this is actually sort of happening, but slowly, and autoconf is likely to stick around for a while, if only as a compatibility layer during the transition.)
As a user I highly appreciate ./configure for the --help flag, which usually tells me how to build a program with or without particular functionalities which may or may not be applicable to my use-case.
I actually think this is possible to improve if you have the autoconf files. You could parse it to find all the checks you know can run in parallel and run those.
It is possible in theory to speed up existing configure scripts by switching interpreter from /bin/sh to something that scans file, splits it to independent blocks and runs them in parallel.
Historically, different Unixes varied a lot more than they do today. Say you want your program to use the C library function foo on platforms where it’s available and the function bar where it isn’t: You can write both versions and choose between them based on a C preprocessor macro, and the program will use the best option available for the platform where it was compiled.
But now the user has to set the preprocessor macro appropriately when he builds your program. Nobody wants to give the user a pop quiz on the intricacies of his C library every time he goes to install new software. So instead the developer writes a shell script that tries to compile a trivial program that uses function foo. If the script succeeds, it defines the preprocessor macro FOO_AVAILABLE, and the program will use foo; if it fails, it doesn’t define that macro, and the program will fall back to bar.
That shell script grew into configure. A configure script for an old and widely ported piece of software can check for a lot of platform features.
I'm not saying we should send everyone a docker container with a full copy of ubuntu, electron and foo.js whether they have foo in their c library or not, but maybe there is a middle ground?
> JS and Python wouldn't be what they are today if you had to `./configure` every website you want to visit, lmao.
You just gave me a flashback to the IE6 days. Yes, that's precisely what we did. On every page load.
It's called "feature detection", and was the recommended way of doing things (the bad alternative was user agent sniffing, in which you read the user agent string to guess the browser, and then assumed that browser X always had feature Y; the worst alternative was to simply require browser X).
Hands have to get dirty somewhere. "As deep as The Worker's City lay underground, so high above towered the City of Metropolis."
The choices are:
1. Restrict the freedom of CPU designers to some approximation of the PDP11. No funky DSP chips. No crazy vector processors.
2. Restrict the freedom of OS designers to some approximation of Unix. No bespoke realtime OSes. No research OSes.
3. Insist programmers use a new programming language for these chips and OSes. (This was the case prior to C and Unix.)
4. Insist programmers write in assembly and/or machine code. Perhaps a macro-assembler is acceptable here, but this is inching toward C.
The cost of this flexibility is gross tooling to make it manageable. Can it be done without years and years of accrued M4 and sh? Perhaps, but that's just CMake and CMake is nowhere near as capable as Autotools & friends are when working with legacy platforms.
I like C/C++ a lot, A LOT, and I agree with your comment.
Man, if this got fixed it would be one of the best languages to develop for.
My wishlist:
* Quick compilation times (obv.) or some sort of tool that makes it feel like an interpreted language, at least when you're developing, then do the usual compile step to get an optimized binary.
* A F...... CLEAR AND CONSISTENT WAY TO TELL THE TOOLCHAIN THIS LIBRARY IS HERE AND THIS ONE IS OVER THERE (sorry but, come on ...).
* A single command line argument to output a static binary.
* Anything that gets us closer to the "build-once run-anywhere" philosophy of "Cosmopolitan Libc". Even if an intermediate execution layer is needed. One could say, "oh, but this is C, not Java", but it is already de facto a broken Java, because you still need an execution layer, call it stdlib, GLIB, whatever, if those shared libraries are not on your system with their exact version matching, your program breaks ... Just stop pretending and ship the "C virtual machine", lmao.
> is this really a big deal given you run ./configure once
I end up running it dozens of times when changing versions, checking out different branches, chasing dependencies.
It’s a big deal.
> it's like systemd trading off non-determinism for boot speed, when it takes 5 minutes to get through the POST
5 minute POST time is a bad analogy. systemd is used in many places, from desktops (that POST quickly) to embedded systems where boot time is critical.
If deterministic boot is important then you would specify it explicitly. Relying on emergent behavior for consistent boot order is bad design.
The number of systems that have 5 minute POST times and need deterministic boot is an edge case of an edge case.
This aspect of configure, in particular, drives me nuts. Obviously I'd like it to be faster, but it's not the end of the world. I forget what I was trying to build the other week, but I had to make 18 separate runs of configure to find all the things I was missing. When I dug into things it looked like it could probably have done it in 2 runs, each presenting a batch of things that were missing. Instead I got stuck with "configure, install missing package" over and over again.
Exactly. Multiply this with the time it takes for one run on a slow machine. Back in the day, I ran a compilation on my phone as it was the target device. Besides the compilation taking 40 minutes (and configure had missed a thing or two), the configure step itself took a minute or so. Because I don't know all the moving parts, I prefer start from scratch than running into obscure problems later on.
Arguing against parallelization of configure is like arguing against faster OS updates. "It's only once a week/whatever, come on!" Except it's spread over a billion of people time and time again.
And a very large number of those Linux servers are running Linux VMs, which don't POST, use systemd, and have their boot time dominated by the guest OS. Those servers are probably hosting dozens of VMs too. Boot time makes a lot of difference here.
> I end up running it dozens of times when changing versions, checking out different branches, chasing dependencies.
Yeah... but neither of that is going to change stuff like the size of a data type, the endianness of the architecture you're running on, or the features / build configuration of some library the project depends on.
Parallelization is a bandaid (although a sorely needed!) IMHO, C/C++ libraries desperately need to develop some sort of standard that doesn't require a full gcc build for each tiny test. I'd envision something like nodejs's package.json, just with more specific information about the build details themselves. And for the stuff like datatype sizes, that should be provided by gcc/llvm in a fast-parseable way so that autotools can pick it up.
There is the `-C` option of course. It's supposedly good for the standard tests that waste all the time, but not so much for the ad-hoc tests various projects use, which have an unfortunate chance of being buggy or varying across time.
... I wonder if it's possible to manually seed a cache file with only known-safe test results and let it still perform the unsafe tests? Be sure to copy the cache file to a temporary name ...
---
I've thought about rewriting `./configure` in C (I did it in Python once but Python's portability turned out to be poor - Python2 was bug-free but killed; Python3 was unfixably buggy for a decade or so). Still have a stub shell script that reads HOSTCC etc. then quickly builds and executes `./configure.bin`.
If you do a lot of bisecting, or bootstrapping, or building compatibility matrices, or really anything that needs you to compile lots of old versions, the repeated ./configure steps really start feeling like a drag.
In a "reasonably well-behaved program", if you have the artifacts from a current configure, like a "config.h" header, they are compatible with older commits, even if configurations changed, as long as the configuration changes were additive: introducing some new test, along with a new symbol in "config.h".
It's possible to skip some of the ./configure steps. Especially for someone who knows the program very well.
Perhaps you can get away with that for small, young, or self-contained projects. But for medium-to-large projects running more than a few years, the (different versions of) external or vendored dependencies tend to come and go, and they all have their own configurations. Long-running projects are also prone to internal reorganizations and overhauls to the build system. (Go back far enough, and you're having to wrangle patchsets for every few months' worth of versions since -fpermissive is no longer permissive enough to get it to build.)
> it's like systemd trading off non-determinism for boot speed, when it takes 5 minutes to get through the POST
That's a bad analogy: if a given deterministic service ordering is needed for a service to correctly start (say because it doesn't start with the systemd unit), it means the non-deterministic systemd service units are not properly encoding the dependencies tree in the Before= and After=
When done properly, both solutions should work the same. However, the solution properly encoding the dependency graph (instead of just projecting it on a 1-dimensional sequence of numbers) will be more flexible: it's the better solution, because it will give you more speed but also more flexibility: you can see the branches any leaf depends on, remove leaves as needed, then cull the useless branches. You could add determinism if you want, but why bother?
It's like using the dependencies of linux packages, and leaving the job of resolving them to package managers (apt, pacman...): you can then remove the useless packages which are no longer required.
Compare that to doing a `make install` of everything to /usr/local in a specific order, as specified by a script: when done properly, both solutions will work, but one solution is clearly better than the other as it encodes more finely the existing dependencies instead of projecting them to a sequence.
You can add determinism if you want to follow a sequence (ex: `apt-get install make` before adding gcc, then add cuda...), or you can use meta package like build-essentials, but being restricted to a sequence gains you nothing.
Most systems do not have 5 minute POST times. That’s an extreme outlier.
Linux runs all over, including embedded systems where boot time is important.
Optimizing for edge cases on outliers isn’t a priority. If you need specific boot ordering, configure it that way. It doesn’t make sense for the entire Linux world to sacrifice boot speed.
Old machines probably didn't, no, but I have absolutely seen machines (Enterprise™ Servers) that took longer than that to get to the bootloader. IIRC it was mostly a combination of hardware RAID controllers and RAM... something. Testing?
One thing I ran across when trying to figure this out previously - while some firmware is undoubtably dumb, a decent amount of it was that it was doing a lot more than typical PC firmware.
For instance, the slow RAM check POST I was experiencing is because it was also doing a quick single pass memory test. Consumer firmware goes ‘meh, whatever’.
Disk spin up, it was also staging out the disk power ups so that it didn’t kill the PSU - not a concern if you have 3-4 drives. But definitely a concern if you have 20.
Also, the raid controller was running basic SMART tests and the like. Which consumer stuff typically doesn’t.
Now how much any of this is worthwhile depends on the use case of course. ‘Farm of cheap PCs’ type cloud hosting environments, most these types of conditions get handled by software, and it doesn’t matter much if any single box is half broken.
If you have one big box serving a bunch of key infra, and reboot it periodically as part of ‘scheduled maintenance’ (aka old school on prem), then it does.
A fairer criticism would be that they have no sense to use a more sane build system. CMake is a mess but even that is faaaaar saner than autotools, and probably more popular at this point.
[1] https://nostarch.com/autotools2e
This is peak engineering.
I'd like to think of myself as reasonable, so I'll just say that reasonable people may disagree with your assertion that cmake is in any way at all better than autotools.
There is no way in hell anyone reasonable could say that Autotools is better than CMake.
Simple projects: just use plain C. This is dwm, the window manager that spawned a thousand forks. No ./configure in sight: <https://git.suckless.org/dwm/files.html>
If you run into platform-specific stuff, just write a ./configure in simple and plain shell: <https://git.suckless.org/utmp/file/configure.html>. Even if you keep adding more stuff, it shouldn't take more than 100ms.
If you're doing something really complex (like say, writing a compiler), take the approach from Plan 9 / Go. Make a conditionally included header file that takes care of platform differences for you. Check the $GOARCH/u.h files here:
<https://go.googlesource.com/go/+/refs/heads/release-branch.g...>
(There are also some simple OS-specific checks: <https://go.googlesource.com/go/+/refs/heads/release-branch.g...>)
This is the reference Go compiler; it can target any platform, from any host (modulo CGO); later versions are also self-hosting and reproducible.
Software with custom configure scripts are especially dreaded amongst packagers.
Even plain C is easier.
You can have a whole file be for OpenBSD, to work around that some standard library parts have different types on different platforms.
So now you need one file for all platforms and architectures where Timeval.Usec is int32, and another file for where it is int64. And you need to enumerate in your code all GOOS/GOARCH combinations that Go supports or will ever support.
You need a file for Linux 32 bit ARM (int32/int32 bit), one for Linux 64 bit ARM (int64,int64), one for OpenBSD 32 bit ARM (int64/int32), etc…. Maybe you can group them, but this is just one difference, so in the end you'll have to do one file per combination of OS and Arch. And all you wanted was pluggable "what's a Timeval?". Something that all build systems solved a long time ago.
And then maybe the next release of OpenBSD they've changed it, so now you cannot use Go's way to write portable code at all.
So between autotools, cmake, and the Go method, the Go method is by far the worst option for writing portable code.
> So now you need one file for all platforms and architectures where Timeval.Usec is int32, and another file for where it is int64. And you need to enumerate in your code all GOOS/GOARCH combinations that Go supports or will ever support.
I assume you mean [syscall.Timeval]?
Do you have a specific use case for [syscall], where you cannot use [time]?Meh, I used to keep printed copies of autotools manuals. I sympathize with all of these people and acknowledge they are likely the sane ones.
That's what you get for wanting to use a glib function.
Instead of splitting the "configure" and "make" steps though, I chose to instead fold much of the "configure" step into the "make".
To clarify, this article describes a system where `./configure` runs a bunch of compilations in parallel, then `make` does stuff depending on those compilations.
If one is willing to restrict what the configure can detect/do to writing to header files (rather than affecting variables examined/used in a Makefile), then instead one can have `./configure` generate a `Makefile` (or in my case, a ninja file), and then have the "run the compiler to see what defines to set" and "run compiler to build the executable" can be run in a single `make` or `ninja` invocation.
The simple way here results in _almost_ the same behavior: all the "configure"-like stuff running and then all the "build" stuff running. But if one is a bit more careful/clever and doesn't depend on the entire "config.h" for every "<real source>.c" compilation, then one can start to interleave the work perceived as "configuration" with that seen as "build". (I did not get that fancy)
[1]: https://github.com/codyps/cninja/tree/master/config_h
Just from a quick peek at that repo, nowadays you can write
#if __has_attribute(cold)
and avoid the configure test entirely. Probably wasn't a thing 10 years ago though :)
Covers a very large part of what is needed, making fewer and fewer things need to end up in configure scripts. I think most of what's left is checking for items (types, functions) existence and their shape, as you were doing :). I can dream about getting a nice special operator to check for fields/functions, would let us remove even more from configure time, but I suspect we won't because that requires type resolution and none of the existing special operators do that.
This is how it was done: https://github.com/tavianator/tavianator.com/blob/cf0e4ef26d...
It's likely that C will continue to be used by everyone for decades to come, but I know that I'll personally never start a new project in C again.
I'm still glad that there's some sort of push to make autotools suck less for legacy projects.
Creating a make file is about 10 lines and is the lowest friction for me to get programming of any environment. Familiarity is part of that.
But if you don't plan to distribute things widely (or have no deps).. Whatever, just do what works for you.
Autotools is going to check every config from the past 50 years.
No? Most operating systems don't have a separate packager. They have the developer package the application.
autoconf is in no way, shape or form an "official" build system associated with C. It is a GNU creation and certainly popular, but not to a "monopoly" degree, and it's share is declining. (plain make & meson & cmake being popular alternatives)
It can build a Rust program (build.rs) which builds things that aren't Rust, but that's an entirely different use case (building non-Rust library to use inside of Rust programs).
[1] https://www.gnu.org/savannah-checkouts/gnu/autoconf/manual/a...
Also, I was surprised when the animated text at the top of the article wasn't a gif, but actual text. So cool!
Also, you shouldn’t need to run ./configure every time you run make.
Most checks are common, so what can help is having a shared cache for all configure scripts so if you have 400 packages to rebuild, it doesn't check 400 times if you should use flock or fcntl. This approach is described here: https://jmmv.dev/2022/06/autoconf-caching.html
It doesn't help that autoconf is basically abandonware, with one forlorn maintainer trying to resuscitate it, but creating major regressions with new releases: https://lwn.net/Articles/834682/
A far too common tragedy of our age.
*And superficially off the topic of this thread, but possibly not.
But yeah, I agree that we were promised a lot more automatic multithreading than we got. History has proven that we should be wary of any promises that depend on a Sufficiently Smart Compiler.
Maybe it would have been easier if CPU performance didn’t end up outstripping memory performance so much, or if cache coherency between cores weren’t so difficult.
The CPU has better visibility into the actual runtime situation, so can do runtime optimization better.
In some ways, it’s like a bytecode/JVM type situation.
For the trivial example of 2+2 like above, of course, this is a moot discussion. The commenter should've lead with a better example.
And when that happens, almost always the developer knows it is that type of situation and will want to tune things themselves anyway.
At runtime, the CPU can figure it out though, eh?
If I replace it with int buf_size = 10000000; cin >> buf_size; auto vec = make_large_array(buf_size); for (const auto& val : vec) { do_expensive_thing(val); }
the compiler could generate some code that looks like: if buf_size >= SOME_LARGE_THRESHOLD { DO_IN_PARALLEL } else { DO_SERIAL }
With some background logic for managing threads, etc. In a C++-style world where "control" is important it likely wouldn't fly, but if this was python...
could be parallelised at compile time.You want bigger units of work for multiple cores, otherwise the coordination overhead will outweigh the work the application is doing
I think the Erlang runtime is probably the best use of functional programming and multiple cores. Since Erlang processes are shared nothing, I think they will scale to 64 or 128 cores just fine
Whereas the GC will be a bottleneck in most languages with shared memory ... you will stop scaling before using all your cores
But I don't think Erlang is as fine-grained as your example ...
Some related threads:
https://news.ycombinator.com/item?id=40130079
https://news.ycombinator.com/item?id=31176264
AFAIU Erlang is not that fast an interpreter; I thought the Pony Language was doing something similar (shared nothing?) with compiled code, but I haven't heard about it in awhile
A higher level language can be more opinionated, but a low level one shouldn't straight jacket you.
i.e. Rust can be used to IMPLEMENT an Erlang runtime
If you couldn't use threads, then you could not implement an Erlang runtime.
I understand that yours is a very simple example, but a) such things are already parallelized even on a single thread thanks to all the internal CPU parallelism, b) one should always be mindful of Amdahl's law, c) truly parallel solutions to various problems tend to be structurally different from serial ones in unpredictable ways, so there's no single transformation, not even a single family of transformations.
[1] https://github.com/HigherOrderCO/Bend [2] https://github.com/VineLang/vine [3] https://en.wikipedia.org/wiki/Interaction_nets
Oddly enough, functional programming seems to be a poor fit for this because the fanout tends to be fairly low: individual operations have few inputs, and single-linked lists and trees are more common than arrays.
this works best for scientific computing things that run through very big loops where there is very little interaction between iterations
(The conclusion I distilled out of reading that at the time, I think, was that this is actually sort of happening, but slowly, and autoconf is likely to stick around for a while, if only as a compatibility layer during the transition.)
But I wanted the blog post sized version to be simpler for exposition.
Nice writeup though.
Is there any such previous work?
Wait is this true? (!)
But now the user has to set the preprocessor macro appropriately when he builds your program. Nobody wants to give the user a pop quiz on the intricacies of his C library every time he goes to install new software. So instead the developer writes a shell script that tries to compile a trivial program that uses function foo. If the script succeeds, it defines the preprocessor macro FOO_AVAILABLE, and the program will use foo; if it fails, it doesn’t define that macro, and the program will fall back to bar.
That shell script grew into configure. A configure script for an old and widely ported piece of software can check for a lot of platform features.
JS and Python wouldn't be what they are today if you had to `./configure` every website you want to visit, lmao.
You just gave me a flashback to the IE6 days. Yes, that's precisely what we did. On every page load.
It's called "feature detection", and was the recommended way of doing things (the bad alternative was user agent sniffing, in which you read the user agent string to guess the browser, and then assumed that browser X always had feature Y; the worst alternative was to simply require browser X).
The choices are:
1. Restrict the freedom of CPU designers to some approximation of the PDP11. No funky DSP chips. No crazy vector processors.
2. Restrict the freedom of OS designers to some approximation of Unix. No bespoke realtime OSes. No research OSes.
3. Insist programmers use a new programming language for these chips and OSes. (This was the case prior to C and Unix.)
4. Insist programmers write in assembly and/or machine code. Perhaps a macro-assembler is acceptable here, but this is inching toward C.
The cost of this flexibility is gross tooling to make it manageable. Can it be done without years and years of accrued M4 and sh? Perhaps, but that's just CMake and CMake is nowhere near as capable as Autotools & friends are when working with legacy platforms.
Man, if this got fixed it would be one of the best languages to develop for.
My wishlist:
* Quick compilation times (obv.) or some sort of tool that makes it feel like an interpreted language, at least when you're developing, then do the usual compile step to get an optimized binary.
* A F...... CLEAR AND CONSISTENT WAY TO TELL THE TOOLCHAIN THIS LIBRARY IS HERE AND THIS ONE IS OVER THERE (sorry but, come on ...).
* A single command line argument to output a static binary.
* Anything that gets us closer to the "build-once run-anywhere" philosophy of "Cosmopolitan Libc". Even if an intermediate execution layer is needed. One could say, "oh, but this is C, not Java", but it is already de facto a broken Java, because you still need an execution layer, call it stdlib, GLIB, whatever, if those shared libraries are not on your system with their exact version matching, your program breaks ... Just stop pretending and ship the "C virtual machine", lmao.
it's like systemd trading off non-determinism for boot speed, when it takes 5 minutes to get through the POST
I end up running it dozens of times when changing versions, checking out different branches, chasing dependencies.
It’s a big deal.
> it's like systemd trading off non-determinism for boot speed, when it takes 5 minutes to get through the POST
5 minute POST time is a bad analogy. systemd is used in many places, from desktops (that POST quickly) to embedded systems where boot time is critical.
If deterministic boot is important then you would specify it explicitly. Relying on emergent behavior for consistent boot order is bad design.
The number of systems that have 5 minute POST times and need deterministic boot is an edge case of an edge case.
This aspect of configure, in particular, drives me nuts. Obviously I'd like it to be faster, but it's not the end of the world. I forget what I was trying to build the other week, but I had to make 18 separate runs of configure to find all the things I was missing. When I dug into things it looked like it could probably have done it in 2 runs, each presenting a batch of things that were missing. Instead I got stuck with "configure, install missing package" over and over again.
Arguing against parallelization of configure is like arguing against faster OS updates. "It's only once a week/whatever, come on!" Except it's spread over a billion of people time and time again.
I take you don't run DDR5?
if it's critical on an embedded system then you're not running systemd at all
> The number of systems that have 5 minute POST times and need deterministic boot is an edge case of an edge case.
desktop machines are the edge case, there's a LOT more servers running Linux than people using Linux desktops
> Relying on emergent behavior for consistent boot order is bad design.
tell that to the distro authors who 10 years in can't tell the difference between network-online.target, network-pre.target, network.target
amdahl's law's a bitch
Yeah... but neither of that is going to change stuff like the size of a data type, the endianness of the architecture you're running on, or the features / build configuration of some library the project depends on.
Parallelization is a bandaid (although a sorely needed!) IMHO, C/C++ libraries desperately need to develop some sort of standard that doesn't require a full gcc build for each tiny test. I'd envision something like nodejs's package.json, just with more specific information about the build details themselves. And for the stuff like datatype sizes, that should be provided by gcc/llvm in a fast-parseable way so that autotools can pick it up.
... I wonder if it's possible to manually seed a cache file with only known-safe test results and let it still perform the unsafe tests? Be sure to copy the cache file to a temporary name ...
---
I've thought about rewriting `./configure` in C (I did it in Python once but Python's portability turned out to be poor - Python2 was bug-free but killed; Python3 was unfixably buggy for a decade or so). Still have a stub shell script that reads HOSTCC etc. then quickly builds and executes `./configure.bin`.
It's possible to skip some of the ./configure steps. Especially for someone who knows the program very well.
That's a bad analogy: if a given deterministic service ordering is needed for a service to correctly start (say because it doesn't start with the systemd unit), it means the non-deterministic systemd service units are not properly encoding the dependencies tree in the Before= and After=
When done properly, both solutions should work the same. However, the solution properly encoding the dependency graph (instead of just projecting it on a 1-dimensional sequence of numbers) will be more flexible: it's the better solution, because it will give you more speed but also more flexibility: you can see the branches any leaf depends on, remove leaves as needed, then cull the useless branches. You could add determinism if you want, but why bother?
It's like using the dependencies of linux packages, and leaving the job of resolving them to package managers (apt, pacman...): you can then remove the useless packages which are no longer required.
Compare that to doing a `make install` of everything to /usr/local in a specific order, as specified by a script: when done properly, both solutions will work, but one solution is clearly better than the other as it encodes more finely the existing dependencies instead of projecting them to a sequence.
You can add determinism if you want to follow a sequence (ex: `apt-get install make` before adding gcc, then add cuda...), or you can use meta package like build-essentials, but being restricted to a sequence gains you nothing.
given how complicated the boot process is ([1]), and it occurs once a month, I'd rather it was as deterministic as possible
vs. shaving 1% off the boot time
[1]: distros continue to ship subtlety broken unit files, because the model is too complicated
Linux runs all over, including embedded systems where boot time is important.
Optimizing for edge cases on outliers isn’t a priority. If you need specific boot ordering, configure it that way. It doesn’t make sense for the entire Linux world to sacrifice boot speed.
For instance, the slow RAM check POST I was experiencing is because it was also doing a quick single pass memory test. Consumer firmware goes ‘meh, whatever’.
Disk spin up, it was also staging out the disk power ups so that it didn’t kill the PSU - not a concern if you have 3-4 drives. But definitely a concern if you have 20.
Also, the raid controller was running basic SMART tests and the like. Which consumer stuff typically doesn’t.
Now how much any of this is worthwhile depends on the use case of course. ‘Farm of cheap PCs’ type cloud hosting environments, most these types of conditions get handled by software, and it doesn’t matter much if any single box is half broken.
If you have one big box serving a bunch of key infra, and reboot it periodically as part of ‘scheduled maintenance’ (aka old school on prem), then it does.
Competing POST in under 2 minutes is not guaranteed.
Especially the 4 socket beasts with lots of DIMMs.
Unfortunately no one has actually bothered to write down how systemd really works; the closest to a real writeup out there is https://blog.darknedgy.net/technology/2020/05/02/0/