std.getopt uses deprecated rwm operations for shared variables

[dlangBugzillaToGithub]

Seb reported this on 2018-02-05T12:57:36Z

Transferred from https://issues.dlang.org/show_bug.cgi?id=18375

CC List

• ZombineDev

Description

---
shared real v;
shared string s;
auto args = ["program.name", "-v=2", "-s=bar"];
---

[dlangBugzillaToGithub]

greensunny12 commented on 2018-02-05T13:33:24Z

std.getopt test cases:

1) Passing and "just" triggering deprecation warnings


---
@system unittest
{
    shared real v;
    shared uint i;
    shared string[] arrString;
    shared int[] arrInt;

    auto args = ["program.name",
        "-v=2",
        "-i=10",
        "--arrString=a", "--arrString=b",
        "--arrInt=1", "--arrInt=2",
    ];
    getopt(args,
        "v", &v,
        "i", &i,
        "arrString", &arrString,
        "arrInt", &arrInt,
    );
    assert(v == 2);
    assert(i == 10);

    shared expectedArrString = ["a", "b"];
    assert(arrString == expectedArrString);
    shared expectedArrInt = [1, 2];
    assert(arrInt == expectedArrInt);
}
---

2) Completely failing

---
@system unittest
{
    shared string s;
    shared bool b;
    shared string[string] assocArrayString;
    shared double[string] assocArrayDouble;

    auto args = ["program.name",
        "-s=bar",
        "-b",
        "--assocArrayString=foo=bar,bar=1",
        "--assocArrayDouble=foo=1,bar=2",
    ];
    getopt(args,
        "s", &s,
        "b", &b,
        "assocArrayString", &assocArrayString,
        "assocArrayDouble", &assocArrayDouble,
    );

    assert(s == "bar");
    assert(b == 1);

    shared expectedAssocArrayString = ["foo": "bar", "bar": "1"];
    assert(assocArrayString == expectedAssocArrayString);
    shared expectedAssocArrayDouble = ["foo":1.0, "bar": 2];
    assert(assocArrayDouble == expectedAssocArrayDouble);
}
---

[dlangBugzillaToGithub]

petar.p.kirov commented on 2018-02-05T17:23:25Z

All of these examples should *never* compile. The whole point of `shared` is to statically disallow accidental access shared mutable state. > 90% of all functions in phobos have no business touching `shared`/`__gshared` variables, especially `std.getopt`.

`std.getopt` can be safely used to set:
* function local variables
* (static) thread-local variables
* immutable global variables from shared static constructors (not sure if this currently works, but it should be ok from memory model perspective)

I consider everything else to potentially trigger undefined behavior.

[dlangBugzillaToGithub]

greensunny12 commented on 2018-02-05T17:56:47Z

>  immutable global variables from shared static constructors (not sure if this currently works, but it should be ok from memory model perspective)

No this doesn't work at the moment.


For future readers: it has been used by people before (https://github.com/vibe-d/vibe.d/pull/2060).