make functions as c functions (#1921)
make functions as c functions (#1921)

Description: declare functions as c functions (as opposed to c++ functions)
Risk Level: low
Testing: ci
Docs Changes: n/a
Release Notes: n/a

Signed-off-by: Jingwei Hao <87eb6e61b06a9638bebd8a6383dcf233f789f5fe@gmail.com>
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