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Regex: don't overflow the stack on long lines

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libstdc++'s std::regex matcher recurses about once per matched
character, so '.*', 'a+' or '(a|b)*' on a line of a few tens of
thousands of characters (minified JS/JSON) overflowed the 8 MiB stack
and crashed the editor from the regex search prompt or regex replace.

Regex search and regex replace now run their matching on a worker
thread with a 1 GiB reserved stack (RunWithLargeStack; the caller
waits, so nothing is shared concurrently). Renderers skip regex match
highlighting on lines over 10,000 bytes. Catastrophic backtracking
(e.g. (a*)*b) is still possible: std::regex has no time limit.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015rcVQiiWyTzoNrsvLSaAfB
This commit is contained in:
Claude
2026-09-24 09:16:04 -07:00
committed by Kyle Isom
parent 812cde090f
commit 9f3da72765
8 changed files with 136 additions and 23 deletions
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Command.cc
+28 -20
View File
@@ -11,6 +11,7 @@
#include <string_view>
#include "Command.h"
#include "RegexGuard.h"
#include "syntax/HighlighterRegistry.h"
#include "syntax/NullHighlighter.h"
#include "Editor.h"
@@ -797,16 +798,19 @@ search_compute_matches_regex(const Buffer &buf, const std::string &pattern, std:
try {
const std::regex rx(pattern);
const auto &rows = buf.Rows();
for (std::size_t y = 0; y < rows.size(); ++y) {
std::string line = static_cast<std::string>(rows[y]);
for (auto it = std::sregex_iterator(line.begin(), line.end(), rx);
it != std::sregex_iterator(); ++it) {
const auto &m = *it;
out.push_back(RegexMatch{
y, static_cast<std::size_t>(m.position()), static_cast<std::size_t>(m.length())
});
// std::regex recurses per matched character; see RegexGuard.h.
kte::RunWithLargeStack([&] {
for (std::size_t y = 0; y < rows.size(); ++y) {
std::string line = static_cast<std::string>(rows[y]);
for (auto it = std::sregex_iterator(line.begin(), line.end(), rx);
it != std::sregex_iterator(); ++it) {
const auto &m = *it;
out.push_back(RegexMatch{
y, static_cast<std::size_t>(m.position()), static_cast<std::size_t>(m.length())
});
}
}
}
});
} catch (const std::regex_error &e) {
err_out = e.what();
// Return empty results on error
@@ -3212,18 +3216,22 @@ cmd_newline(CommandContext &ctx)
std::size_t nrows = buf->Nrows();
if (nrows > 1 && buf->GetLineString(nrows - 1).empty())
--nrows;
for (std::size_t y = 0; y < nrows; ++y) {
const std::string before = buf->GetLineString(y);
const std::string after = std::regex_replace(before, rx, repl);
if (after != before) {
replace_rows_text(*buf, y, before, after, ru);
// A replacement containing newlines adds rows; skip past them.
const auto added = static_cast<std::size_t>(std::count(after.begin(), after.end(), '\n'));
y += added;
nrows += added;
++changed;
// std::regex recurses per matched character; see RegexGuard.h. The
// caller waits for the worker, so the buffer is never shared.
kte::RunWithLargeStack([&] {
for (std::size_t y = 0; y < nrows; ++y) {
const std::string before = buf->GetLineString(y);
const std::string after = std::regex_replace(before, rx, repl);
if (after != before) {
replace_rows_text(*buf, y, before, after, ru);
// A replacement containing newlines adds rows; skip past them.
const auto added = static_cast<std::size_t>(std::count(after.begin(), after.end(), '\n'));
y += added;
nrows += added;
++changed;
}
}
}
});
clamp_cursor_to_buffer(*buf);
buf->SetDirty(true);
ctx.editor.SetStatus("Regex replaced in " + std::to_string(changed) + " line(s)");