cosmopolitan VS glibc

The reality is a bit different, the work on Python 3.6 was checked into the Cosmopolitan repo and I have been able to use it for production workloads that are in pure python. [0]

As Cosmopolitan Libc has evolved, it has been possible to compile more software without modifications, and that includes latest Python through a project called superconfigure[1].

Last person who tried to reproduce it from scratch did it last week (granted it too them a few days of solid work) but in the end they ended with a portable binary with Python 3.11.9, brotli, ssl and asyncio for their work related project.[2]

[0] https://github.com/jart/cosmopolitan/tree/master/third_party...

Cosmopolitan https://github.com/jart/cosmopolitan and https://justine.lol/cosmopolitan/index.html

Some genius realized that you can actually embed valid win32 programs inside valid posix shell scripts, and found a way to make a C cross-platform solution out of it, meaning that you can write C programs that compile to a single executable that will run on (quoting the site) Linux + Mac + Windows + FreeBSD + OpenBSD + NetBSD + BIOS

It all started from this post.

For this .args file, put one argument per line. This will run on start. You can use `/zip/mydepencency.anything` to read from files, but if you have an executable dependency you'll need to extract it first.

You can do this with any software you can compile with comsocc, by adding a call to LoadZipArgs[1] in the main function.

It'seasy to get started, your ideas will branch out as soon as you start playing with it.

[1]: https://github.com/jart/cosmopolitan/blob/master/tool/args/a...

FWIW there is ongoing work with good progress to add websocket support to redbean (https://github.com/jart/cosmopolitan/pull/967)

Check out this comment by jart (cosmpolitan author) here: https://github.com/jart/cosmopolitan/issues/766#issuecomment...

it might help but not sure how comprehensive it is! would it be a bad idea for you to check out the source code of other popular emulators (maybe iTerm 2^0) ?

0: https://github.com/search?q=repo%3Agnachman%2FiTerm2%20ansi&...

The binary was compiled with Cosmopolitan Libc [0], and therefore the binary will execute natively on Linux, Mac, Windows, FreeBSD, OpenBSD, NetBSD, and bare metal (BIOS boot).

I would call that portable.

[0] https://github.com/jart/cosmopolitan

will go on my "to try" list where i already have cosmopolitan [2]. my last setup (windows) was shiv + wine + nsis (used that as pyinstaller had some issues)[2]

[1] https://github.com/jart/cosmopolitan/issues/141#issuecomment...

I wonder if you’re using a different definition of ‘vectorized’ from the one I would use. For example glibc provides a vectorized strlen. Here is the sse version: https://github.com/bminor/glibc/blob/master/sysdeps/x86_64/m...

It’s pretty simple to imagine how to write an unoptimized version: read a vector from the start of the string, compare it to 0, convert that to a bitvector, test for equal to zero, then loop or clz and finish.

I would call this vectorized because it operates on 16 bytes (sse) at a time.

There are a few issues:

1. You’re still spending a lot of time in the scalar code checking loop conditions.

2. You’re doing unaligned reads which are slower on old processors

3. You may read across a cache line forcing you to pull a second line into cache even if the string ends before then.

4. You may read across a page boundary which could cause a segfault if the next page is not accessible

So the fixes are to do 64-byte (ie cache line) aligned accesses which also means page-aligned (so you won’t read from a page until you know the string doesn’t end in the previous page). That deals with alignment problems. You read four vector registers at a time but this doesn’t really cost much more if the string is shorter as it all comes from one cache line. Another trick in the linked code is that it first finds the cache line by reading the first 16 bytes then merging in the next 3 groups with unsigned-min, so it only requires one test against a zero vector instead of 4. Then it finds the zero in the cache line. You need to do a bit of work in the first iteration to become aligned. With AVX, you can use mask registers on reads to handle that first step instead.

That was also my thought. To my knowledge `/etc/localtime` is the creation of Arthur David Olson, the founder of the tz database (now maintained by IANA), but his code never read `/etc/localtime` multiple times unless `TZ` environment variable was changed. Tzcode made into glibc but Ulrich Drepper changed it to not cache `/etc/localtime` when `TZ` is unset [1]; I wasn't able to locate the exact rationale, given that the commit was very ancient (1996-12) and no mailing list archive is available for this time period.

[1] https://github.com/bminor/glibc/commit/68dbb3a69e78e24a778c6...

That's not really what the problem is. The actual code is fine.

The issue is that the definition of `fd_set` has a constant size [1]. If you allocate the memory yourself, the select() system call will work with as many file descriptors as you care to pass to it. You can see that both glibc [2] and the kernel [3] support arbitrarily large arrays.

[1] https://github.com/bminor/glibc/blob/master/misc/sys/select....

[2] https://github.com/bminor/glibc/blob/master/sysdeps/unix/sys...

[3] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/lin...

The source code for that is here.

Expanding macro gives three GCC function attributes [2]: `__attribute__ ((malloc))`, `__attribute__ ((alloc_size(1)))` and `__attribute__ ((warn_unused_result))`. They are required for GCC (and others recognizing them) to actually ensure that they behave as the standard dictates. Your own malloc-like functions won't be treated same unless you give similar attributes.

[1] https://github.com/bminor/glibc/blob/807690610916df8aef17cd1...

[2] https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attribute...

IFunc relocations is what enables glibc to dynamically choose the best memcpy routine to use at runtime based on the CPU.

see https://github.com/bminor/glibc/blob/glibc-2.31/sysdeps/x86_...

memmove can be very well implemented in pure C, libc implementations usually have a "generic" (meaning, architecture independent) fallback. Here is musl generic implementation and its x86-64 assembly implementation. For glibc, implementation is a bit more complex, having multiple architectures implemented, but you could find a generic implementation with these two files: memmove.c and generic/memcopy.h.

Yeah, looks like the Q_strcat(pszContentPath, "/"); is invalid, as glibc has only allocated exactly enough to fit the path in the buffer returned by realpath().

Interestingly, the open group spec says that a null argument to realpath is "Implementation defined" [0]

And the linux (glibc) man pages say it allocates a buffer "Up to PATH_MAX" [1]

I guess "strlen(path)" is "Up to PATH_MAX", but the man page seems unclear - you could read that as implying the buffer is always allocated to PATH_MAX size, but that's not what seems to be happening, just effectively calling strdup() [2]. I have no idea how to feed back to the linux man pages, but might be worth clarifying there.

[0] https://pubs.opengroup.org/onlinepubs/009696799/functions/re...

[1] https://linux.die.net/man/3/realpath

[2] https://github.com/bminor/glibc/blob/0b9d2d4a76508fdcbd9f421...

For the actual sources you will have to look at one of the mirrors of the C standard library, such as https://github.com/bminor/glibc/tree/master/sysdeps/ieee754/dbl-64