Skip to content

Fix out-of-bounds slice in TrimLeadingSQLComments for single-character lines #834

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
dossy merged 2 commits into from
Sep 15, 2026
Merged

Fix out-of-bounds slice in TrimLeadingSQLComments for single-character lines #834

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
457d97e
Fix out-of-bounds slice in TrimLeadingSQLComments for single-characte…
MattBridges Sep 5, 2026
ad440df
fix: use bytes.HasPrefix and add a test that reproduces the dropped line
dossy Sep 15, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
2 changes: 1 addition & 1 deletion pkg/dbutil/dbutil.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -71,7 +71,7 @@ func TrimLeadingSQLComments(data []byte) ([]byte, error) {
// we read bytes directly for premature performance optimization
line := scanner.Bytes()

if preamble && (len(line) == 0 || bytes.Equal(line[0:2], []byte("--"))) {
if preamble && (len(line) == 0 || bytes.HasPrefix(line, []byte("--"))) {
// header section, skip this line in output buffer
continue
}
Expand Down
19 changes: 19 additions & 0 deletions pkg/dbutil/dbutil_test.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@ package dbutil_test

import (
"database/sql"
"strings"
"testing"

"github.com/amacneil/dbmate/v2/pkg/dbtest"
Expand Down Expand Up @@ -36,6 +37,24 @@ func TestTrimLeadingSQLComments(t *testing.T) {
require.Equal(t, "real stuff\n-- end\n", string(out))
}

func TestTrimLeadingSQLCommentsShortLineAtEOF(t *testing.T) {
// >4KB of leading comments forces bufio.Scanner to slide its buffer,
// leaving stale bytes just past the final token; a one-byte last line
// must not be misread as a comment marker.
var b strings.Builder
for b.Len() < 4090 {
b.WriteString("--\n")
}
for b.Len() < 4095 {
b.WriteString("-")
}
b.WriteString("\n-") // final line: one byte, no trailing newline

out, err := dbutil.TrimLeadingSQLComments([]byte(b.String()))
require.NoError(t, err)
require.Equal(t, "-\n", string(out))
}

func TestStripPsqlMetaCommands(t *testing.T) {
t.Run("strips restrict and unrestrict", func(t *testing.T) {
in := "\\restrict dbmate\n" +
Expand Down