Is stdout.flush() unsafe?

Steven Schveighoffer via Digitalmars-d-learn digitalmars-d-learn at
Tue Dec 29 11:15:28 PST 2015

On 12/29/15 4:57 AM, tsbockman wrote:
> Trying to compile this:
> void main() @safe
> {
>      import std.stdio;
>      stdout.flush();
> }
> Fails with this message:
>> Error: safe function 'main' cannot access __gshared data 'stdout'
> Is this necessary? If so, what are the synchronization requirements for
> access to `stdout`?

Hm... what is needed is an accessor for stdout:

void main() @safe
    import std.stdio;
    auto safe_stdout() @trusted { return stdout; }

The issue is the storage class __gshared is banned from accessing in 
safe code (because it is subject to races). So you have to claim to the 
compiler "I know this is generally not safe, but I have encapsulated it 
in a way to make it safe". Likely, this is what we should do for all the 
standard streams, not being able to access streams in safe code seems a 
steep restriction.


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