njh/contiki — comment on commit 974ab3f246bfdd8be41df8c3eca56b9016195e0b
File:  line 0
By dak664:

The static ... = 0 adds overhead and flash, storing the zeroes in flash and copying them to .data variables at startup. gcc puts variables with no initializer into .bss and zeros that block efficiently.

Opinions may differ, but mine is we can safely assume uninitialized static variables are zero.