C51: Warning 206 (Missing Function Prototype)

Information in this article applies to:

• C51 Version 5.50

QUESTION

While compiling my C source file, the compiler reported the following diagnostic:

WARNING 206: MISSING FUNCTION PROTOTYPE

ANSWER

The called function is unknown because no prototype declaration exists. Calls to unknown functions risk that the number of parameters may not correspond to the actual requirements. If this is the case, the function is called incorrectly.

The compiler has no way to check for missing or excessive parameters and their types. Include prototypes of the functions used in your program. Prototypes must be specified before the functions are actually called. The definition of a function automatically produces a prototype.

MORE INFORMATION

• Refer to Warning C206 in the Cx51 User's Guide.

Last Reviewed: Thursday, February 25, 2021