I try to use sqrt(l) in my program, l is a long int, but
the compiler reported amibigous call:
temp\3122(13) : error C2668: 'sqrt' : ambiguous call to
overloaded function
while I compile it in my VC6, it's all ok,

and when I use hypot function, it reported linker error:
3589.obj : error LNK2001: unresolved external symbol _hypot
temp/3589.exe : fatal error LNK1120: 1 unresolved externals
that means you have the function in your header file, but
you cut it in your library file or you delete the whole
library, it's terrible, I don't know for any reason it can
become a restricted function.

as i remember,the ANSI sqrt() is :

double sqrt(double x)