git: gpt(8): Fix surrogate pair handling bug in utf16_to_utf8()

[Aaron LI]

commit 62207d04fe9a976a6127b4950ed82632bd154815
Author: Aaron LI <aly at aaronly.me>
Date:   Wed Jan 21 17:17:55 2026 +0800

    gpt(8): Fix surrogate pair handling bug in utf16_to_utf8()
    
    * The old code mishandled surrogate pairs and thus failed to recognize
      valid UTF-16 characters and would replace them with 0xFFFD.  Fix the
      code to correctly handle the surrogate pairs.
    
    * Fix an out-of-bound access in the old code when it tried to handle the
      surrogate pairs.  Check `s16idx < s16len` before accessing it with
      `le16toh(s16[s16idx])`.
    
    * Remove the `if (utfchar < 0x200000)` branch, because it's impossible
      for `utfchar` exceeding 0x200000.
    
    * Tweak the `while` loop conditional to clean up the code.
    
    Credit: ChatGPT (https://chatgpt.com/)

Summary of changes:
 sbin/gpt/gpt.c | 40 +++++++++++++++++++++++++---------------
 1 file changed, 25 insertions(+), 15 deletions(-)

http://gitweb.dragonflybsd.org/dragonfly.git/commitdiff/62207d04fe9a976a6127b4950ed82632bd154815


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