#pragma c99(“implicit” | “no%implicit”)
This pragma controls diagnostics for implicit function declarations. If the c99 pragma value is set to “implicit” (note the use of quotation marks), a warning is generated when the compiler finds an implicit function declaration. If the c99 pragma value is set to “no%implicit” (note the use of quotation marks) the compiler silently accepts implicit function declaration until the pragma value is reset.
The value of the -std option affects the default state of this pragma. For -std=c11 or -std=c99, the default state is #pragma c99(“implicit”). For -std=c89, the default state is #pragma c99(“no%implicit”).