file path on my machine is:
C:\Users\david\AppData\Local\Arduino15\packages\arduino\hardware\mbed_giga\4.0.10\libraries\Portenta_SDRAM\src\SDRAM.h
need to add
#ifndefsdramh
#definesdramh
at beginning of file
and
#endif
at end of file

To reproduce
include "sdram.h" twice

Expected behavior
not generate linker error

Arduino IDE version 2.2.1 updated to nightly build 12/14/2023

Operating system
Windows

Operating system version
windows 11