Mixing
Is it possible to declare 2 static mutable variables depending on each other?
3
I am trying to declare two static mutable variables but I have a error:
static mut I: i64 = 5;
static mut J: i64 = I + 3;
fn main() {
unsafe {
println!("I: {}, J: {}", I, J);
}
}
Error:
error[E0133]: use of mutable static is unsafe and requires unsafe function or block
--> src/main.rs:2:21
|
2 | static mut J: i64 = I + 3;
| ^ use of mutable static
|
= note: mutable statics can be mutated by multiple threads: aliasing violations or data races will cause undefined behavior
Is it impossible? I also tried to put an unsafe block on the declaration but it seems to be incorrect grammar:
static mut I: i64 = 5;
unsafe {
static mut J: i64 = I + 3;
}
rust
edited Nov 19 '18 at 15:18
Shepmaster
148k12283417
asked Nov 19 '18 at 14:43
Victor Polevoy
6,88133688
add a comment |
3
I am trying to declare two static mutable variables but I have a error:
static mut I: i64 = 5;
static mut J: i64 = I + 3;
fn main() {
unsafe {
println!("I: {}, J: {}", I, J);
}
}
Error:
error[E0133]: use of mutable static is unsafe and requires unsafe function or block
--> src/main.rs:2:21
|
2 | static mut J: i64 = I + 3;
| ^ use of mutable static
|
= note: mutable statics can be mutated by multiple threads: aliasing violations or data races will cause undefined behavior
Is it impossible? I also tried to put an unsafe block on the declaration but it seems to be incorrect grammar:
static mut I: i64 = 5;
unsafe {
static mut J: i64 = I + 3;
}
rust
edited Nov 19 '18 at 15:18
Shepmaster
148k12283417
asked Nov 19 '18 at 14:43
Victor Polevoy
6,88133688
1
Not sure about your usecase, but this is a bad idea to do so, unless you really know what you do.
– Boiethios
Nov 19 '18 at 14:51
1
Global, static, mutable variables are pure evil! Uselazy_static!, RefCell or a Mutex, if you really have to, but I would avoid them at all cost!
– hellow
Nov 19 '18 at 14:57
@hellow Oh, guys, of course I know that, I was just curious whether I can do so or not, because, you know, when I saw that I could not do this even withunsafeblock, I was stuck. I haven't had a real use case for this by now, but I wanted to know whether it was possible in general or not.
– Victor Polevoy
Nov 20 '18 at 7:55
add a comment |
3
3
3
I am trying to declare two static mutable variables but I have a error:
static mut I: i64 = 5;
static mut J: i64 = I + 3;
fn main() {
unsafe {
println!("I: {}, J: {}", I, J);
}
}
Error:
error[E0133]: use of mutable static is unsafe and requires unsafe function or block
--> src/main.rs:2:21
|
2 | static mut J: i64 = I + 3;
| ^ use of mutable static
|
= note: mutable statics can be mutated by multiple threads: aliasing violations or data races will cause undefined behavior
Is it impossible? I also tried to put an unsafe block on the declaration but it seems to be incorrect grammar:
static mut I: i64 = 5;
unsafe {
static mut J: i64 = I + 3;
}
rust
edited Nov 19 '18 at 15:18
Shepmaster
148k12283417
asked Nov 19 '18 at 14:43
Victor Polevoy
6,88133688
I am trying to declare two static mutable variables but I have a error:
static mut I: i64 = 5;
static mut J: i64 = I + 3;
fn main() {
unsafe {
println!("I: {}, J: {}", I, J);
}
}
Error:
error[E0133]: use of mutable static is unsafe and requires unsafe function or block
--> src/main.rs:2:21
|
2 | static mut J: i64 = I + 3;
| ^ use of mutable static
|
= note: mutable statics can be mutated by multiple threads: aliasing violations or data races will cause undefined behavior
Is it impossible? I also tried to put an unsafe block on the declaration but it seems to be incorrect grammar:
static mut I: i64 = 5;
unsafe {
static mut J: i64 = I + 3;
}
rust
rust
edited Nov 19 '18 at 15:18
Shepmaster
148k12283417
asked Nov 19 '18 at 14:43
Victor Polevoy
6,88133688
edited Nov 19 '18 at 15:18
Shepmaster
148k12283417
asked Nov 19 '18 at 14:43
Victor Polevoy
6,88133688
edited Nov 19 '18 at 15:18
Shepmaster
148k12283417
edited Nov 19 '18 at 15:18
Shepmaster
148k12283417
edited Nov 19 '18 at 15:18
Shepmaster
148k12283417
148k12283417
asked Nov 19 '18 at 14:43
Victor Polevoy
6,88133688
asked Nov 19 '18 at 14:43
Victor Polevoy
6,88133688
asked Nov 19 '18 at 14:43
Victor Polevoy
6,88133688
6,88133688
1
Not sure about your usecase, but this is a bad idea to do so, unless you really know what you do.
– Boiethios
Nov 19 '18 at 14:51
1
Global, static, mutable variables are pure evil! Uselazy_static!, RefCell or a Mutex, if you really have to, but I would avoid them at all cost!
– hellow
Nov 19 '18 at 14:57
@hellow Oh, guys, of course I know that, I was just curious whether I can do so or not, because, you know, when I saw that I could not do this even withunsafeblock, I was stuck. I haven't had a real use case for this by now, but I wanted to know whether it was possible in general or not.
– Victor Polevoy
Nov 20 '18 at 7:55
add a comment |
1
Not sure about your usecase, but this is a bad idea to do so, unless you really know what you do.
– Boiethios
Nov 19 '18 at 14:51
1
Global, static, mutable variables are pure evil! Uselazy_static!, RefCell or a Mutex, if you really have to, but I would avoid them at all cost!
– hellow
Nov 19 '18 at 14:57
@hellow Oh, guys, of course I know that, I was just curious whether I can do so or not, because, you know, when I saw that I could not do this even withunsafeblock, I was stuck. I haven't had a real use case for this by now, but I wanted to know whether it was possible in general or not.
– Victor Polevoy
Nov 20 '18 at 7:55
1
1
Not sure about your usecase, but this is a bad idea to do so, unless you really know what you do.
– Boiethios
Nov 19 '18 at 14:51
Not sure about your usecase, but this is a bad idea to do so, unless you really know what you do.
– Boiethios
Nov 19 '18 at 14:51
1
1
Global, static, mutable variables are pure evil! Use
lazy_static!, RefCell or a Mutex, if you really have to, but I would avoid them at all cost!– hellow
Nov 19 '18 at 14:57
Global, static, mutable variables are pure evil! Use
lazy_static!, RefCell or a Mutex, if you really have to, but I would avoid them at all cost!– hellow
Nov 19 '18 at 14:57
@hellow Oh, guys, of course I know that, I was just curious whether I can do so or not, because, you know, when I saw that I could not do this even with
unsafe block, I was stuck. I haven't had a real use case for this by now, but I wanted to know whether it was possible in general or not.– Victor Polevoy
Nov 20 '18 at 7:55
@hellow Oh, guys, of course I know that, I was just curious whether I can do so or not, because, you know, when I saw that I could not do this even with
unsafe block, I was stuck. I haven't had a real use case for this by now, but I wanted to know whether it was possible in general or not.– Victor Polevoy
Nov 20 '18 at 7:55
add a comment |
1 Answer
1
active
oldest
votes
8
Yes it is.
In your case, just remove mut, because static globals are safe to access, because they cannot be changed and therefore do not suffer from all the bad attributes, like unsynchronized access.
static I: i64 = 5;
static J: i64 = I + 3;
fn main() {
println!("I: {}, J: {}", I, J);
}
If you want them to be mutable, you can use unsafe where you access the unsafe variable (in this case I).
static mut I: i64 = 5;
static mut J: i64 = unsafe { I } + 3;
fn main() {
unsafe {
println!("I: {}, J: {}", I, J);
}
}
answered Nov 19 '18 at 14:49
hellow
4,78532042
Holys... I did not know it was possible to putunsafeso... Thanks.
– Victor Polevoy
Nov 20 '18 at 7:53
add a comment |
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
8
Yes it is.
In your case, just remove mut, because static globals are safe to access, because they cannot be changed and therefore do not suffer from all the bad attributes, like unsynchronized access.
static I: i64 = 5;
static J: i64 = I + 3;
fn main() {
println!("I: {}, J: {}", I, J);
}
If you want them to be mutable, you can use unsafe where you access the unsafe variable (in this case I).
static mut I: i64 = 5;
static mut J: i64 = unsafe { I } + 3;
fn main() {
unsafe {
println!("I: {}, J: {}", I, J);
}
}
answered Nov 19 '18 at 14:49
hellow
4,78532042
Holys... I did not know it was possible to putunsafeso... Thanks.
– Victor Polevoy
Nov 20 '18 at 7:53
add a comment |
8
Yes it is.
In your case, just remove mut, because static globals are safe to access, because they cannot be changed and therefore do not suffer from all the bad attributes, like unsynchronized access.
static I: i64 = 5;
static J: i64 = I + 3;
fn main() {
println!("I: {}, J: {}", I, J);
}
If you want them to be mutable, you can use unsafe where you access the unsafe variable (in this case I).
static mut I: i64 = 5;
static mut J: i64 = unsafe { I } + 3;
fn main() {
unsafe {
println!("I: {}, J: {}", I, J);
}
}
answered Nov 19 '18 at 14:49
hellow
4,78532042
Holys... I did not know it was possible to putunsafeso... Thanks.
– Victor Polevoy
Nov 20 '18 at 7:53
add a comment |
8
8
8
Yes it is.
In your case, just remove mut, because static globals are safe to access, because they cannot be changed and therefore do not suffer from all the bad attributes, like unsynchronized access.
static I: i64 = 5;
static J: i64 = I + 3;
fn main() {
println!("I: {}, J: {}", I, J);
}
If you want them to be mutable, you can use unsafe where you access the unsafe variable (in this case I).
static mut I: i64 = 5;
static mut J: i64 = unsafe { I } + 3;
fn main() {
unsafe {
println!("I: {}, J: {}", I, J);
}
}
answered Nov 19 '18 at 14:49
hellow
4,78532042
Yes it is.
In your case, just remove mut, because static globals are safe to access, because they cannot be changed and therefore do not suffer from all the bad attributes, like unsynchronized access.
static I: i64 = 5;
static J: i64 = I + 3;
fn main() {
println!("I: {}, J: {}", I, J);
}
If you want them to be mutable, you can use unsafe where you access the unsafe variable (in this case I).
static mut I: i64 = 5;
static mut J: i64 = unsafe { I } + 3;
fn main() {
unsafe {
println!("I: {}, J: {}", I, J);
}
}
answered Nov 19 '18 at 14:49
hellow
4,78532042
edited Nov 19 '18 at 15:39
answered Nov 19 '18 at 14:49
hellow
4,78532042
answered Nov 19 '18 at 14:49
hellow
4,78532042
answered Nov 19 '18 at 14:49
hellow
4,78532042
4,78532042
Holys... I did not know it was possible to putunsafeso... Thanks.
– Victor Polevoy
Nov 20 '18 at 7:53
add a comment |
Holys... I did not know it was possible to putunsafeso... Thanks.
– Victor Polevoy
Nov 20 '18 at 7:53
Holys... I did not know it was possible to put
unsafe so... Thanks.– Victor Polevoy
Nov 20 '18 at 7:53
Holys... I did not know it was possible to put
unsafe so... Thanks.– Victor Polevoy
Nov 20 '18 at 7:53
add a comment |
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1
Not sure about your usecase, but this is a bad idea to do so, unless you really know what you do.
– Boiethios
Nov 19 '18 at 14:51
1
Global, static, mutable variables are pure evil! Use
lazy_static!, RefCell or a Mutex, if you really have to, but I would avoid them at all cost!– hellow
Nov 19 '18 at 14:57
@hellow Oh, guys, of course I know that, I was just curious whether I can do so or not, because, you know, when I saw that I could not do this even with
unsafeblock, I was stuck. I haven't had a real use case for this by now, but I wanted to know whether it was possible in general or not.– Victor Polevoy
Nov 20 '18 at 7:55