How do I inform Windows that I'm writing a binary file? • Hacker News Board

Re: How do I inform Windows that I'm writing a binary file?

#21

Post by gmueckl » Thu, May 07, 2026, 2:31 AM UTC

userbinator wrote: post #18

ChrisSD wrote: post #5

Earlier quoted context omitted.

The Win32 API. E.g. using WriteFile to write files ( https://learn.microsoft.com/en-us/windows/win32/api/fileapi/... ) It wasn't until fairly recently that the C runtime was stably shipped with Windows. Previously you had to install the correct version of the C library alongside your application.

It wasn't until fairly recently By "recently" you mean Win95? MSVCRT.DLL has been there for at least that long.

I believe that it technically belongs to Visual C++, not the operating system, but it needs to ship with the OS because the user space binaries are compiled with MSVC.

Re: How do I inform Windows that I'm writing a binary file?

#22

Post by jcranmer » Thu, May 07, 2026, 2:36 AM UTC

lmm wrote: post #4

The article seems to be taking the position that the C runtime library is not part of "Windows", which feels like a rather odd view to me. What is the stable API that Windows offers to application developers if not that?

There is a very unfortunate situation in Unix systems in that the library named 'libc' is serving several simultaneous different roles. One of those roles--what it is named for--is serving as the C standard library. The more important role is that the library also provides the implementation of a different standard API, the POSIX API, which is the main API used to access system details. There's also yet another role of providing the stable system interface to the kernel in most Unix implementations. On Windows, these roles are provided by different libraries: ucrt (what used to be msvcrt), kernel32, and ntdll, respectively.

And for what it's worth, the actual C standard library tends to be fairly rarely used, especially if you consider the malloc/free interface to be part of the system library rather than the C standard library. The C stdio functionality, for example, is extremely underpowered compared to the capabilities of all major operating systems' I/O libraries, and so most applications--even those written entirely in C--will choose to avoid the C standard library and instead use the more direct primitives of the system API layer instead.

Re: How do I inform Windows that I'm writing a binary file?

#23

Post by Joker_vD » Thu, May 07, 2026, 2:39 AM UTC

anitil wrote: post #20

criddell wrote: post #12

Earlier quoted context omitted.

Linefeed (\n) is a single byte in DOS as well. I think you are talking about carriage return linefeed pair (CRLF or \r\n), These control codes go back to line printers. Linefeed advances the paper one line and carriage return moves the print head to the left.

Annoyingly I actually think '\r\n' is the correct line ending here - advance the paper and return the carriage, but I suppose unix took the simpler implementation which makes looping over characters, words (split by ' ') and lines (split by '\n') simpler as each loop only has a single comparison

Yep, on Unixen the translation of CRLF to LF when printing to the terminal (and from CR to CRLF when reading input from the terminal) is done in the kernel, it's called "line discipline".

Re: How do I inform Windows that I'm writing a binary file?

#24

Post by wpollock » Thu, May 07, 2026, 2:45 AM UTC

Interestingly, the IETF has several published RFCs for text protocols, all of which require \r\n line endings.

https://www.rfc-editor.org/old/EOLstory.txt>

Note this does not apply to file formats (except for RFCs).

Re: How do I inform Windows that I'm writing a binary file?

#25

Post by dboreham » Thu, May 07, 2026, 2:45 AM UTC

userbinator wrote: post #18

ChrisSD wrote: post #5

Earlier quoted context omitted.

The Win32 API. E.g. using WriteFile to write files ( https://learn.microsoft.com/en-us/windows/win32/api/fileapi/... ) It wasn't until fairly recently that the C runtime was stably shipped with Windows. Previously you had to install the correct version of the C library alongside your application.

It wasn't until fairly recently By "recently" you mean Win95? MSVCRT.DLL has been there for at least that long.

It was there but mystery meat vs whatever version you might need for your binary.

Re: How do I inform Windows that I'm writing a binary file?

#26

Post by ack_complete » Thu, May 07, 2026, 2:48 AM UTC

gmueckl wrote: post #21

userbinator wrote: post #18

Earlier quoted context omitted.

It wasn't until fairly recently By "recently" you mean Win95? MSVCRT.DLL has been there for at least that long.

I believe that it technically belongs to Visual C++, not the operating system, but it needs to ship with the OS because the user space binaries are compiled with MSVC.

It's both. Originally Visual C++ binaries built for DLL-based C runtime relied on MSVCRT.DLL and that was installed by the redist. Starting with Visual Studio .NET 2002, separate CRT DLLs starting with MSVCR70.DLL were used. MSVCRT.DLL is now part of Windows to support parts of the OS itself and for compatibility with programs that still use it. I think some versions of MinGW also use MSVCRT.

Current versions of the OS ship with functions in MSVCRT.DLL that weren't in the last VC6 version, such as the updated C++ exception handler (__CxxFrameHandler4). AFAIK, there is no redistributable version of it, it's unique to the OS.

Re: How do I inform Windows that I'm writing a binary file?

#27

Post by Joker_vD » Thu, May 07, 2026, 2:49 AM UTC

lmm wrote: post #9

ChrisSD wrote: post #5

Earlier quoted context omitted.

The Win32 API. E.g. using WriteFile to write files ( https://learn.microsoft.com/en-us/windows/win32/api/fileapi/... ) It wasn't until fairly recently that the C runtime was stably shipped with Windows. Previously you had to install the correct version of the C library alongside your application.

> The Win32 API. E.g. using WriteFile to write files ( https://learn.microsoft.com/en-us/windows/win32/api/fileapi/ ...) Which is called from what, if not C? Does windows really offer no API for writing text (rather than bytes) to files? Or does it rely on the application developer to manage line endings in their own code? Neither of those sounds very developer-friendly.

From literally any language. The WriteFile function comes from kernel32.dll shared library, and follows the certain calling convention. You don't need to use this calling convention inside your own binary (and indeed, MinGW and MSYS use SysV ABI for everything except when calling Win32 API), or ask a random C runtime coming from God knows where to do this for you if you write something other than C.

In the UNIX world there is this strange notion that C language is somehow special and that the OS itself should provide its runtime (a single global version of it) for every program, even those written in other languages, to interact with the OS but... it's just silly.

> Does windows really offer no API for writing text (rather than bytes) to files? Or does it rely on the application developer to manage line endings in their own code? Neither of those sounds very developer-friendly.

No it doesn't. That logic belongs in the OS-specific layer in the runtimes/standard libraries of the implementations of the different programming languages. They may decide to re-use each other libraries, of course, or they may decide not to.

Re: How do I inform Windows that I'm writing a binary file?

#28

Post by userbinator » Thu, May 07, 2026, 2:56 AM UTC

dboreham wrote: post #25

userbinator wrote: post #18

Earlier quoted context omitted.

It wasn't until fairly recently By "recently" you mean Win95? MSVCRT.DLL has been there for at least that long.

It was there but mystery meat vs whatever version you might need for your binary.

They are backwards-compatible. I've written many tiny (few KB) utilities that work from Win95 through Win11, and of course WINE.

Re: How do I inform Windows that I'm writing a binary file?

#29

Post by poizan42 » Thu, May 07, 2026, 3:19 AM UTC

Joker_vD wrote: post #23

anitil wrote: post #20

Earlier quoted context omitted.

Annoyingly I actually think '\r\n' is the correct line ending here - advance the paper and return the carriage, but I suppose unix took the simpler implementation which makes looping over characters, words (split by ' ') and lines (split by '\n') simpler as each loop only has a single comparison

Yep, on Unixen the translation of CRLF to LF when printing to the terminal (and from CR to CRLF when reading input from the terminal) is done in the kernel, it's called "line discipline".

And if you switch the tty from "cooked" to "raw" mode then it doesn't do the conversion, and a CR just moves the cursor back to the start of the line and a LF just moves the cursor one line down.

Re: How do I inform Windows that I'm writing a binary file?

#30

Post by Joker_vD » Thu, May 07, 2026, 3:19 AM UTC

lmm wrote: post #16

p_l wrote: post #11

Earlier quoted context omitted.

The whole issue is specific to C and languages that copied C or use its runtime underneath in implementations (like Python) For reference, Unix has no API other than bytes either.

> The whole issue is specific to C and languages that copied C or use its runtime underneath in implementations (like Python) So it's "specific to" almost all programming languages in actual use. That's a rather esoteric point. > For reference, Unix has no API other than bytes either. Unix does offer an API for writing C-standard in-memory text strings to Unix-standard on-disk text files, it just happens to be the sa…

> Unix does offer an API for writing C-standard in-memory text strings

Why on bloody Earth should a presumably generic-purpose OS provide a special API for dealing with internal representation of some data structure in a (particular) implementation of a (particular) programming language?

Besides, it doesn't offer such an API anyhow; you need to take care to manually pass the result of a strlen() call instead of sizeof()'s as the value for the len parameter of a write() call, otherwise a NUL-terminator will get written into the file as well.

And C says nothing about what constitutes a line break, by the way. Nor does it have any concept of a "line", or any utilities for working with lines specifically, it only knows of strings, and that's all. The concept of "text line" is POSIX.