Function Pointer as an Argument in C

trutnev · 05-23-2005, 10:33 PM

more particulary, i need it for qsort function. when I do it like this

qsort( table, size, sizeof( element), &compare);

compiler tells me

warning: passing arg 4 of `qsort' from incompatible pointer type

compare is defined as a normal function.

what is wrong here ?

thank you.

Harmaa Kettu · 05-23-2005, 11:03 PM

The "&" character is not needed there.

See "man bsearch" for example code.

trutnev · 05-23-2005, 11:17 PM

there is no example in my man for bsearch nor for qsort. just generic informations about the usage.

could you post here your man with the example ?

thanks in advance.

Quote:

Originally posted by Harmaa Kettu
The "&" character is not needed there.

See "man bsearch" for example code.

Harmaa Kettu · 05-24-2005, 01:24 AM

Online version here.

ta0kira · 05-24-2005, 01:47 AM

Make sure your function is a 'int(const void*, const void*)' otherwise it won't work: you can't use:

Code:

int compare(int A, int B)
{ return A < B; }

You would need:

Code:

int compare(const void *A, const void *B)
{ return *((const int*) A) < *((const int*) B) ;}

ta0kira

trutnev · 05-24-2005, 10:22 AM

thank you