[Issue 12642] New: Avoid some heap allocation cases for fixed-size arrays

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=12642

          Issue ID: 12642
           Summary: Avoid some heap allocation cases for fixed-size arrays
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: DMD
          Assignee: nobody at puremagic.com
          Reporter: bearophile_hugs at eml.cc

The @nogc annotation of dmd 2.066alpha refuses the following programs:


__gshared int[1] data1;
int[1] bar() @nogc {
    int x;
    return [x];
}
void main() @nogc {
    int x;
    data1 = [x];
    int[1] data2;
    data2 = [x];
}


test.d(4,12): Error: array literals in @nogc function bar may cause GC
allocation
test.d(8,13): Error: array literals in @nogc function main may cause GC
allocation
test.d(10,13): Error: array literals in @nogc function main may cause GC
allocation


But is it possible to avoid heap allocations in those cases, to allow those
programs to compile?


This similar code compiles:

__gshared int[1] data1;
int[1] bar() @nogc {
    int x;
    typeof(return) tmp;
    tmp[0] = x;
    return tmp;
}
void main() @nogc {
    int x;
    data1[0] = x;
    int[1] data2;
    data2[0] = x;
}

--