I have programs running for years on previous Arduino versions (1.8.13 and earlier).
I installed now the current 1.8.16 and get several errors on compilation:
Repeating tens times on similar lines:
c:\program files (x86)\arduino-1-8-16\hardware\tools\avr\avr\include\stdlib.h:300:21: error: 'size_t' was not declared in this scope extern void *malloc(size_t __size) ATTR_MALLOC;"
Another error that repeats itself for each print and println command:
error: 'class HardwareSerial' has no member named 'print'; did you mean 'Print'?
error: 'class HardwareSerial' has no member named 'println'; did you mean 'Print'?
(Its certainly with an L, not I, and its shown in red, recognized as command.
The Serial has been initialized: Serial.begin(115200);).
the libraries I use (same as for 1.8.13):
My guess is that the version is missing a header file, but this is for experts.