Re: Range non-emptyness assertions and opIndex
On Friday, 1 July 2016 at 11:35:40 UTC, ag0aep6g wrote: Huh? Asserts are ignored with -release. The only exception is assert(false) which terminates the program immediately, even with -release. Aha, that's what I was testing against so therefore the confusion.
Re: Range non-emptyness assertions and opIndex
On Friday, 1 July 2016 at 10:35:04 UTC, Nordlöw wrote:
I think this is a important issue since asserts are not
optimized away in release mode and D is very much about
performance.
Asserts are removed in release mode, enforce isn't. Here's an
example:
=
void main(string[] args)
{
assert(args.length >= 1);
}
=
dmd testfile.d
This calls the assert function as expected:
=
_Dmain:
: 55 pushrbp
0001: 48 8B EC mov rbp,rsp
0004: 48 83 39 01cmp qword ptr
[rcx],1
0008: 73 0E jae
0018
000A: B9 03 00 00 00 mov ecx,3
000F: 48 83 EC 20sub rsp,20h
0013: E8 00 00 00 00 call
_D5test28__assertFiZv
0018: 31 C0 xor eax,eax
001A: 5D pop rbp
001B: C3 ret
=
Now compiling in release mode:
dmd -release testfile.d
No assert in sight:
=
_Dmain:
: 55 pushrbp
0001: 48 8B EC mov rbp,rsp
0004: 31 C0 xor eax,eax
0006: 5D pop rbp
0007: C3 ret
=
Re: Range non-emptyness assertions and opIndex
On 07/01/2016 12:35 PM, Nordlöw wrote:
What's the preferred way of reacting to emptyness in the members front,
back, popFront, popBack --- using assert, enforce, throw, or simply
relying on range-checking in the _store?
I think assert is the most common way of checking. Simply ignoring the
possibility is also common, as it's considered a programming error to
call front/popFront/etc on an empty range.
For the same reason, throwing an exception (via throw or via enforce) is
less common. Exceptions are more for input/environment errors, not so
much for programming errors.
And what about using
debug assert()
instead of
assert()
typically when `_store`s `opIndex` already performs range-checking?
I think this is a important issue since asserts are not optimized away
in release mode and D is very much about performance.
Huh? Asserts are ignored with -release. The only exception is
assert(false) which terminates the program immediately, even with -release.
A little example program:
void main()
{
import std.stdio;
int x = 1;
assert(x != 1);
writeln("hi");
}
When compiled without -release, the program throws an AssertError. With
-release it prints "hi".
Range non-emptyness assertions and opIndex
If I have a typical range definition like the following
struct Range
{
@safe pure @nogc:
bool empty() const nothrow
{
return _i == _j;
}
size_t length() const nothrow
{
return _j - _i;
}
bool front() const
{
assert(!empty); // TODO use enforce when it's
@nogc
return _store[_i];
}
bool back() const
{
assert(!empty); // TODO use enforce when it's
@nogc
return _store[_j - 1];
}
void popFront()
{
assert(!empty);
++_i;
}
void popBack()
{
assert(!empty);
++_i;
}
private:
BitSet _store; // copy of store
size_t _i = 0; // iterator into _store
size_t _j = _store.length;
}
What's the preferred way of reacting to emptyness in the members
front, back, popFront, popBack --- using assert, enforce, throw,
or simply relying on range-checking in the _store?
And what about using
debug assert()
instead of
assert()
typically when `_store`s `opIndex` already performs
range-checking?
I think this is a important issue since asserts are not optimized
away in release mode and D is very much about performance.
