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digitalmars.D.bugs - [Issue 6247] New: Disallow static mutable variables definitions in pure functions


           Summary: Disallow static mutable variables definitions in pure
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Keywords: diagnostic
          Severity: enhancement
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: bearophile_hugs eml.cc

This is a spinoff of bug 4031

This program:

pure int foo() {
    static int x = 1;
    return x; // line 3
void main() {}

In DMD 2.053 it generates an error in returning x:
test.d(3): Error: pure function 'foo' cannot access mutable static data 'x'

The error message is  but I suggest to disallow the definition of static
mutable data too, this means disallowing line 2 too.

But mutable static variables can't be used in pure functions, so it's better to
really disallow them, and produce a compile error at line 2 too, because
there's no point in allowing their definition and disallowing just their usage.

Some answers to yebblies, from bug 4031:

 I'm not sure if disabling mutable static variables inside pure functions is
 valid, as some actions on them (eg. returning their address) do make sense.
Returning the address of a static variable defined inside a pure function? I don't see the purpose of this. It smells.
 They can also be accessed from any statements inside debug {}.
But this need is probably uncommon, and when this needs arises you are able to move the definition of such variable inside the debug: pure int foo(int x) { debug { static int y = 10; } return x; } void main() {} -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Jul 04 2011