Hang after connecting, main window never shown: tabs.ini with an empty section "[]" #2637

Description

After opening a session, HeidiSQL never shows its main window and hangs ("Not responding"). The session manager works fine; the hang starts right after clicking "Open". It survived a Windows reboot and a
reinstall of HeidiSQL.

The trigger is %APPDATA%\HeidiSQL\tabs.ini: with that file renamed, HeidiSQL opens and connects in ~2 seconds.

Tested launching with heidisql.exe -d="<session>", one change at a time:

• unchanged → hangs
• main window position / maximized state reset in the registry → hangs
• tabs.ini moved away → works

The only anomaly in that tabs.ini is a tab section with an empty name [], whose backup file is query-tab-.sql (no timestamp). The other tab and both .sql backup files look normal (1–2 KB of plain
SQL, no control characters). I don't know how the empty section was created; its backup file was last written on 2026-10-13.

Possibly related: #1224 (tabs.ini writing problems), and a comment in #200 describing a hang while restoring tabs.

HeidiSQL version and OS

12.21.0.7344, Windows 11 Pro for Workstations 23H2 (build 22631), 64-bit

Database server version

MariaDB 11.3.2 (localhost), library libmariadb.dll

Reproduction recipe

1. Close HeidiSQL.
2. Use this as %APPDATA%\HeidiSQL\tabs.ini (my original file; both backup files it points to exist):

[]
BackupFilename=C:\Users\<user>\AppData\Roaming\HeidiSQL\Backups\query-tab-.sql
Caption=Consulta
pid=31644
EditorHeight=208
HelpersWidth=196
TabFocused=0
EditorTopLine=22
[2026-10-13_11-09-09-438]
BackupFilename=C:\Users\<user>\AppData\Roaming\HeidiSQL\Backups\query-tab-2026-10-13_11-09-09-438.sql
pid=31644
EditorHeight=208
HelpersWidth=200
EditorTopLine=1
TabFocused=0

3. Start HeidiSQL and open any session (or run heidisql.exe -d="<session>").

Result: the process keeps running and the connection is established, but the main window never appears and the app is not responding. Waited more than 15 minutes.

Expected: a malformed tab entry is skipped or given a new ID, and HeidiSQL starts normally.

Workaround: close HeidiSQL and rename or delete tabs.ini.

Error/Backtrace

No exception, no madExcept dialog. Observed while hung:
  - heidisql.exe running, TCP connection to ::1:3306 ESTABLISHED
  - TMainForm window exists but is not visible (WS_VISIBLE not set)
  - IsHungAppWindow() = TRUE; ShowWindow() from another process blocks forever
  - main thread uses ~10% of one core continuously; private memory stable (~33 MB)
  - server side the connection is idle; when the process is killed MariaDB logs:
    Aborted connection N to db: '<db>' user: '<user>' host: 'localhost' (Got an error reading communication packets)