• via Digitalmars-d-bugs (45/45) Mar 16 2017 https://issues.dlang.org/show_bug.cgi?id=17261

via Digitalmars-d-bugs <digitalmars-d-bugs puremagic.com> writes:

https://issues.dlang.org/show_bug.cgi?id=17261

          Issue ID: 17261
           Summary: Implicit cast from static array to immutable should
                    not be allowed
           Product: D
           Version: D2
          Hardware: x86_64
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P1
         Component: dmd
          Assignee: nobody puremagic.com
          Reporter: hsteoh quickfur.ath.cx

Code:
--------
import std.stdio;

char[32] func() {
    char[32] staticArr = "A123456789abcdefB123456789abcdef"; // canary
    return staticArr; // OK, by-value return
}

string gunk() {
    string x = func(); // implicit conversion char[16] -> string
    writeln(x.ptr);
    writeln(x);
    return x;
}

void main() {
    auto s = gunk();
    writeln(s.ptr);
    writeln(s);
}
--------


Output:
--------
7FFCD89895C0
A123456789abcdefB123456789abcdef
7FFCD89895C0
9abcdef ����
--------


Basically, func() returns a static array by value, so it resides on the stack.
The implicit conversion in gunk() produces a slice of this stack data (red
flag), which gets corrupted (overwritten) when it returns to main().

Implicitly casting static arrays to immutable should not be allowed.

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