[b84330808]

This change and the description below were written by an LLM (Claude Code).

With the * repeater, the h/H case in unpack() leaves size at -1. The a/A/Z cases set size to the number of bytes they consumed, but the hex case never does, so inputpos += size moves the position one byte backwards instead of to the end of the input. Any format code after h* or H* then re-reads data that was already consumed:

unpack("H*a/H*b", "\xab\xcd");
// ["a" => "abcd", "b" => "abcd"], expected "b" => "" like "a*a/a*b"

unpack("H*a/Cb", "\xab\xcd");
// ["a" => "abcd", "b" => 171], expected the "Type C: not enough input values" warning and false, like "a*a/Cb"

unpack("Ca/H*b/X/Cc", "\x01\xab\xcd");
// "c" => 1 (re-reads byte 0), expected 205 (the last byte)

The fix sets size to the number of input bytes the nibbles came from, (len + 1) / 2. For explicit counts that's the value it already had, so only the * case changes.

The new phpt fails without the fix, and ext/standard/tests/strings passes with it.

Targeting PHP-8.4 as the lowest branch that still gets bug fixes. PHP-8.5 and up have the same bug, but the surrounding lines differ, so the merge-up needs the same line added by hand.