adf88 opened the ticket and wrote:

This is a dormant bug, now the code works but only through accident.

From r10006 different signals are allowed on a single tile. When loading a savegame file v63 or older signal type/variant bits (m2 bits 0..2) are being duplicated (at m2 bits 4..6). The code responsible for this is inside afterload.cpp around line 1505:

SetSignalStates(t, GB(_m[t].m2, 4, 4));
SetSignalVariant(t, INVALID_TRACK, GetSignalVariant(t, TRACK_X));
SetSignalType(t, INVALID_TRACK, GetSignalType(t, TRACK_X));
ClrBit(_m[t].m2, 7);

You can see SetSignalType and SetSignalVariant. BUT these two functions changed in r10006 when PBS'es were added, we have new functions operating on new bits. Currently signal type occupies 3 bits, not 2. Also signal variant bits changed from bit 2 to bit 3. The code works only because the signal variant bit is carried with signal type (it produces invalid signal types for a while!). It may cause whole sort of problems, especially if one tries to change signal bits again.

I'm attaching a patch to fix the issue.

Attachments

• fix-signal-type-variant-loading-for-v63-or-older_r25753.diff (0.98 KiB)

Reported version: Version?
Operating system: All

This issue was imported from FlySpray: https://bugs.openttd.org/task/5732