Linux Kills Strncpy

This article is a bit misleading. Linux kernel programming uses C, but not the C standard library and never has. The string functions discussed here are "helper" functions included in the kernel and are not part of the standard library.

The C standard library doesn't have strscpy or the others; it still has strncpy.

Starting with "The C string library" made me instantly tune out. C has a standard library, which has some string-related functions. There is no "C string library".

BTW: I was experimenting a bit more with string and string view (strv) types in my e toy library: https://codeberg.org/uecker/noplate/

The tests are maybe better examples than those on godbolt. https://codeberg.org/uecker/noplate/src/branch/main/tests/st...

Previously: https://news.ycombinator.com/item?id=48612943

When a wordpress site has more ads than arstechnica.

strncpy was originally used to write into fixed length buffers[1]. This becomes obvious when considering the padding behavior, as described in the C standard[2]: "If the array pointed to by s2 is a string that is shorter than n characters, null characters are appended to the copy in the array pointed to by s1, until n characters in all have been written."

strlcpy, often touted as a replacement, does not elicit the padding behavior but has another flaw: It is supposed to return the length of the string it tried to create, for example, so the user can call realloc without calling strlen again.[3] However, this final "strlen-tail" in strlcpy isn't bounded by the size parameter which describes dest, not src.

While strscpy is a marked improvement, there is still something to be careful about: It can read past the end of the src-buffer, when sizeof src < sizeof dest and src is not nul-terminated.[4] (Set the count argument to something like min(sizeof dest, sizeof src) to avoid that).

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[1] - https://softwareengineering.stackexchange.com/a/438090

[2] - https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3220.pdf, 7.26.2.5 p. 3

[3] - https://manpages.debian.org/jessie/libbsd-dev/strlcpy.3.en.h...

[4] - https://manpages.debian.org/testing/linux-manual-4.8/strscpy...

Not going with something already widely deployed (like strlcpy), which could also be used in userland (strscpy can't, it's return value in case of failure is out of scope) is exactly what I would expect from Linux. You do you!

As I expected, this is about removing strncpy() from the Linux Kernel, not glib.

Removing strncpy() from glib would be awful for applications :)

Edit. Meant glibc, thanks mattst88

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