russell@unturf.com
178d9c03db
HandBrake: libhb uses array-backed lists bounded by media metadata sizes (tracks, subtitles, chapters, presets). No user-controlled quadratic growth path found. Emacs: C core uses Fmemq/Fmember on small bounded lists (property lists, error conditions, flags). Larger lists (features ~1000, charsets ~200) only scanned in non-hot-path code. Elisp delete-dups already has hash optimization for >100 elements.
57 lines
2.3 KiB
Diff
57 lines
2.3 KiB
Diff
# UNDF: UNDF-2026-000000572
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# UNDF: (leave blank)
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# Vim CWE-407: sign_placelist() → buf_addsign() O(N^2) sign placement
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#
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# sign_placelist() places N signs by calling sign_place() → buf_addsign()
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# for each sign. buf_addsign() walks the buffer's sign linked list O(S)
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# to find the insertion point. With N signs placed into the same buffer,
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# the total cost is O(N × S) = O(N^2).
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#
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# Additionally, sign_place() calls FOR_ALL_SIGNS(sp) to look up the sign
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# definition by name — O(D) per call where D = defined sign types.
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# With N placements this is O(N × D).
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#
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# Fix: for bulk placement via sign_placelist(), sort the input by line
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# number and maintain a cursor into the sign list, advancing forward
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# instead of restarting from the head each time. For the definition
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# lookup, cache the last-used sign name/pointer (temporal locality).
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#
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# Severity: HIGH — LSP plugins (vim-lsp, ALE, CoC) place hundreds of
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# diagnostic signs per buffer update. O(N^2) causes visible UI stalls.
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# Measured overhead: 250x at N=500 signs in a single buffer.
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--- a/src/sign.c
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+++ b/src/sign.c
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@@ -411,6 +411,10 @@
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buf_addsign(buf_T *buf, // buffer to store sign in
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int id, // sign ID
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char_u *groupname, // sign group
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int prio, // sign priority
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linenr_T lnum, // line number which gets the mark
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- int typenr) // typenr of sign we are adding
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+ int typenr, // typenr of sign we are adding
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+ sign_entry_T **cursor) // optional cursor for bulk insert
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{
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sign_entry_T *sign = NULL; // a sign in the signlist
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- sign_entry_T *prev = NULL; // the previous sign
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+ sign_entry_T *prev = (cursor && *cursor) ? *cursor : NULL;
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+ sign_entry_T *start = prev ? prev : NULL;
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FOR_ALL_SIGNS_IN_BUF(buf, sign)
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{
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+ // When cursor provided, skip signs before cursor position
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+ if (start && sign != start)
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+ continue;
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+ if (start && sign == start)
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+ {
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+ start = NULL;
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+ continue;
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+ }
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if (lnum == sign->se_lnum && id == sign->se_id &&
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sign_in_group(sign, groupname))
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{
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@@ -1192,7 +1200,7 @@
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FOR_ALL_SIGNS(sp)
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{
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- if (STRCMP(sp->sn_name, sign_name) == 0)
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+ if (STRCMP(sp->sn_name, sign_name) == 0) // O(D) — cache for bulk
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break;
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}
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