fix(section_list): fix binary search overflow and linked list boundary

[0xfullex]

Summary

• Fix integer overflow in binary search calculations
• Fix linked list removal for single-element list edge case

Changes

Binary Search Integer Overflow Fix

Changed the mid-point calculation formula in three binary search locations to prevent integer overflow:

Before (vulnerable to overflow):

mid = (left + right) / 2;
mid = (left + right) / 2 + (left + right) % 2;

After (safe):

mid = left + (right - left) / 2;
mid = left + (right - left + 1) / 2;  // for ceiling division

Affected functions:

• article_block_find_by_aid() - two binary search loops
• section_list_find_article_with_offset() - one binary search loop

Linked List Boundary Condition Fix

In section_list_move_topic(), when removing an article from a single-element list:

Before (bug):

// After setting head/tail to NULL, still tried to update neighbor pointers
p_article->p_prior->p_next = p_article->p_next;
p_article->p_next->p_prior = p_article->p_prior;

After (fixed):

if (p_section_src->p_article_head == p_article) // Single element list
{
    p_section_src->p_article_head = NULL;
    p_section_src->p_article_tail = NULL;
}
else
{
    // Only update neighbor pointers if list is not empty after removal
    p_article->p_prior->p_next = p_article->p_next;
    p_article->p_next->p_prior = p_article->p_prior;
}

Test Plan

• Compile verification
• Test with large article counts to verify binary search
• Test moving topics from single-article sections

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