hippietrail hippietrail - 2 months ago 6
Perl Question

Why don't scripting languages output Unicode to the Windows console?

The Windows console has been Unicode aware for at least a decade and perhaps as far back as Windows NT. However for some reason the major cross-platform scripting languages including Perl and Python only ever output various 8-bit encodings, requiring much trouble to work around. Perl gives a "wide character in print" warning, Python gives a charmap error and quits. Why on earth after all these years do they not just simply call the Win32 -W APIs that output UTF-16 Unicode instead of forcing everything through the ANSI/codepage bottleneck?

Is it just that cross-platform performance is low priority? Is it that the languages use UTF-8 internally and find it too much bother to output UTF-16? Or are the -W APIs inherently broken to such a degree that they can't be used as-is?

UPDATE

It seems that the blame may need to be shared by all parties. I imagined that the scripting languages could just call

wprintf
on Windows and let the OS/runtime worry about things such as redirection. But it turns out that even wprintf on Windows converts wide characters to ANSI and back before printing to the console!

Please let me know if this has been fixed since the bug report link seems broken but my Visual C test code still fails for wprintf and succeeds for WriteConsoleW.

UPDATE 2

Actually you can print UTF-16 to the console from C using
wprintf
but only if you first do
_setmode(_fileno(stdout), _O_U16TEXT)
.

From C you can print UTF-8 to a console whose codepage is set to codepage 65001, however Perl, Python, PHP and Ruby all have bugs which prevent this. Perl and PHP corrupt the output by adding additional blank lines following lines which contain at least one wide character. Ruby has slightly different corrupt output. Python crashes.

UPDATE 3

Node.js is the first scripting language that shipped without this problem straight out of the box.

The Python dev team slowly came to realize this was a real problem since it was first reported back at the end of 2007 and has seen a huge flurry of activity to fully understand and fully fix the bug in 2016.

Answer

The main problem seems to be that it is not possible to use Unicode on Windows using only the standard C library and no platform-dependent or third-party extensions. The languages you mentioned originate from Unix platforms, whose method of implementing Unicode blends well with C (they use normal char* strings, the C locale functions, and UTF-8). If you want to do Unicode in C, you more or less have to write everything twice: once using nonstandard Microsoft extensions, and once using the standard C API functions for all other operating systems. While this can be done, it usually doesn't have high priority because it's cumbersome and most scripting language developers either hate or ignore Windows anyway.

At a more technical level, I think the basic assumption that most standard library designers make is that all I/O streams are inherently byte-based on the OS level, which is true for files on all operating systems, and for all streams on Unix-like systems, with the Windows console being the only exception. Thus the architecture many class libraries and programming language standard have to be modified to a great extent if one wants to incorporate Windows console I/O.

Another more subjective point is that Microsoft just did not enough to promote the use of Unicode. The first Windows OS with decent (for its time) Unicode support was Windows NT 3.1, released in 1993, long before Linux and OS X grew Unicode support. Still, the transition to Unicode in those OSes has been much more seamless and unproblematic. Microsoft once again listened to the sales people instead of the engineers, and kept the technically obsolete Windows 9x around until 2001; instead of forcing developers to use a clean Unicode interface, they still ship the broken and now-unnecessary 8-bit API interface, and invite programmers to use it (look at a few of the recent Windows API questions on Stack Overflow, most newbies still use the horrible legacy API!).

When Unicode came out, many people realized it was useful. Unicode started as a pure 16-bit encoding, so it was natural to use 16-bit code units. Microsoft then apparently said "OK, we have this 16-bit encoding, so we have to create a 16-bit API", not realizing that nobody would use it. The Unix luminaries, however, thought "how can we integrate this into the current system in an efficient and backward-compatible way so that people will actually use it?" and subsequently invented UTF-8, which is a brilliant piece of engineering. Just as when Unix was created, the Unix people thought a bit more, needed a bit longer, has less financially success, but did it eventually right.

I cannot comment on Perl (but I think that there are more Windows haters in the Perl community than in the Python community), but regarding Python I know that the BDFL (who doesn't like Windows as well) has stated that adequate Unicode support on all platforms is a major goal.