I'm not sure I understand the safety of function pointers vs. the
addresses of functions. The code below illustrates the issue.
I was under the impression that pointers are not allowed in safe
code. Naturally, I took that to also mean that function pointers
are not allowed in safe code. Indeed, I haven't been able to pass
a function pointer to a safe function. However, I am able to take
the address of a function and pass that as a parameter. It seems
to work fine for taking the address of functions and templates
(so long as I !)
import std.stdio : writeln;
import std.traits;
import std.math;
void function_safety(T)(T fp)
{
if (functionAttributes!fp & FunctionAttribute.safe)
writeln("fp is safe");
else if (functionAttributes!fp & FunctionAttribute.trusted)
writeln("fp is trusted");
else if (functionAttributes!fp & FunctionAttribute.system)
writeln("fp is system");
else
writeln("fp is neither safe nor trusted nor system");
}
void main()
{
function_safety(&cbrt); //prints fp is trusted
real function(real) fp = &cbrt;
function_safety(fp); //prints fp is system
}
One other related issue. The code above works for some parts of
std.math, but it doesn't for all of it. I thought it was that
some of them are defined in other places, so I used static import
and tried
function_safety(&std.math.cos);
but I'm still getting this error (other people seem to have an
issue with linking and getting it, but I'm not making any other
change and shouldn't need to link anything).
OPTLINK (R) for Win32 Release 8.00.17
Copyright (C) Digital Mars 1989-2013 All rights reserved.
http://www.digitalmars.com/ctg/optlink.html
[path]\AppData\Local\Temp\.rdmd\rdmd-testing_fp_template_purity.d-A5DD
C99AC50E1539BAB8627648C9740B\objs\testing_fp_template_purity.exe.obj(testing_fp_
template_purity.exe)
Error 42: Symbol Undefined _D3std4math3cosFNaNbNiNfeZe
--- errorlevel 1
