Cannot call @system funciton (stdout)

[Steven Schveighoffer]

On 8/16/20 6:07 AM, Simen Kjærås wrote:
> On Saturday, 15 August 2020 at 23:59:36 UTC, Joel wrote:
>> ../../JMiscLib/source/jmisc/base.d(176,2): Error: @safe function 
>> jmisc.base.upDateStatus!string.upDateStatus cannot call @system 
>> function std.stdio.makeGlobal!"core.stdc.stdio.stdout".makeGlobal
>> /Library/D/dmd/src/phobos/std/stdio.d(4837,20): 
>> std.stdio.makeGlobal!"core.stdc.stdio.stdout".makeGlobal is declared here
>>
>> I got around it by avoiding 'stdout'.
> 
> First, what's wrong with using writeln and friends instead of directly 
> mucking about with stdout? :p
> 
> stdout is __gshared, so it's available on any thread at any time. That's 
> not @safe, so it's @system.
> 
> If you know you're not using stdout from multiple threads, or don't care 
> (it might be perfectly safe even though it's possible to misuse), you 
> can use this code:
> 
> @property File trustedStdout() @trusted
> {
>      return stdout;
> }
> 
> That's a @trusted wrapper that you can call from @safe code. It's not 
> actually safe though, as multiple threads could be using trustedStdout 
> at the same time. In many use cases, this is unlikely to matter, but 
> it's wroth keeping in mind.

Technically, there's nothing unsafe about reading stdout, as long as you 
are not setting it. Otherwise, writeln wouldn't be @safe (as all it does 
is call a private trustedStdout).

The whole thing is messy IMO, and should be revisited.

-Steve