Null pointer dereference on empty menu

[lfoxdev]

Menu with no items

Steps to reproduce

1. Make a typycal setup with ESP8266/ESP32
2. Create GEMPage with no parentMenuPage and do not add any items
3. Show the page
4. You will get LoadProhibited exception in console and MCU reboots

Cause

GEMPage after constructing has null _menuItem. GEMPage::getMenuItem checks _menuItem->hidden, so null pointer dereference happens.

Fix

Add check for _menuItem != nullptr to the beginning of GEMPage::getMenuItem (and also GEMPage::getMenuItemNum)

Menu with all hidden items

Steps to reproduce

1. Make a typycal setup with ESP8266/ESP32
2. Create GEMPage with no parentMenuPage
3. Add some items, but hide them all
4. Show the page
5. Press Cancel, Left or Right button
6. You will get LoadProhibited exception in console and MCU reboots

Cause

GEM_u8g2::dispatchKeyPress calls _menuPageCurrent->getCurrentMenuItem()->type in lines 1204, 1213 and _menuPageCurrent->getMenuItem(0)->type in line 1218 (GEM_u8g2.cpp), but getMenuItem() and getCurrentMenuItem() would return nullptr when all elements are hidden.

Fix

Add check for nullptr in the lines above (i have not viewed GLCD and Adafruit version, but i suspect this problem as well as there)

N.B. It seems this problem can't be observed with Atmega MCU's because of no memory access control, but this code still has undefined behaviour, and its operating on Arduinos may rely on luck.

[Spirik]

Thank you for reporting these 🙏 ! Will fix in the next few days.

[Spirik]

Fixed in the 1.6.5 release. Additional checks for null pointer dereference and menu items count added. Tested on ESP32, RP2040 and Uno R4 boards with U8g2 and Adafruit GFX versions.

Thank you!