c - passing function parameters without type, then declare pointers to variables with same names -

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i reading through gnu c library - date-time - data & functions , came across function definition:

int timeval_subtract (result, x, y)  struct timeval *result, *x, *y; {     //do stuff     return result; } 

i have never come across argument passing before. -there not type variables within parenthesis (). -ok type "struct timeval" comes later, using same variable names?

is above entirely equivalent

int struct_timeval(struct timeval *result, struct timeval *x, struct timeval *y){      //do stuff } 

or not?

it old style of function declaration. uses identifier list in declaration.

this kind of declaration not equivalent function prototypes. prototype, function arguments converted type of parameters if assignment without prototype default argument promotion occurs.