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Comment by ahoka

1 day ago

"strncpy() is a weird function with a crappy API."

Well if you bother looking up that it's originally created for non null-terminated strings, then it kinda makes sense.

The real problem begun when static analyzers started to recommend using it instead of strcpy (the real alternative used to be snprintf, now strlcpy).

7 comments

ahoka

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manwe150  1 day ago

strlcpy is a BSD-ism that isn't in posix. The official recommendation is stpecpy. Unfortunately, it is only implemented in the documentation, but not available anywhere unless you roll your own:

https://man7.org/linux/man-pages/man7/string_copying.7.html

tourist2d  1 day ago

Your comment makes no sense. If it was designed for non-null terminated strings, why would it specifically pad after a null terminator?

I looked up the actual reason for its inception:

---

    Rationale for the ANSI C Programming Language", Silicon Press 1990.

    4.11.2.4 The strncpy function
    strncpy was initially introduced into the C library to deal with fixed-length name fields in structures such as directory entries. Such fields are not used in the same way as strings: the trailing null is unnecessary for a maximum-length field, and setting trailing bytes for shorter names to null assures efficient field-wise comparisons. strncpy is not by origin a "bounded strcpy," and the Committee has preferred to recognize existing practice rather than alter the function to better suit it to such use.

  • masklinn  1 day ago

    > If it was designed for non-null terminated strings, why would it specifically pad after a null terminator?

    Padded and terminated strings are completely different beasts. And the text you quote tells you black on white that strncpy deals in padded strings.

  • bentley  1 day ago

    “fixed-length name fields in structures such as directory entries”

    “the trailing null is unnecessary for a maximum-length field”

    That is a non–null terminated string.