Is bool guaranteed to be 1 byte?
The Rust documentation is vague on bool's size.
Is it guaranteed to be 1 byte, or is it unspecified like in C++?
fn main() {
use std::mem;
println!("{}",mem::size_of::<bool>()); //always 1?
}
size rust primitive-types
edited Jun 27 '16 at 13:53
Shepmaster
150k13291430
asked Jun 27 '16 at 6:26
Trevor HickeyTrevor Hickey
16.7k1393187
add a comment |
The Rust documentation is vague on bool's size.
Is it guaranteed to be 1 byte, or is it unspecified like in C++?
fn main() {
use std::mem;
println!("{}",mem::size_of::<bool>()); //always 1?
}
size rust primitive-types
edited Jun 27 '16 at 13:53
Shepmaster
150k13291430
asked Jun 27 '16 at 6:26
Trevor HickeyTrevor Hickey
16.7k1393187
1
This is related to stackoverflow.com/q/36924530/5189607
– malbarbo
Jul 1 '16 at 22:04
See also What is the correct type for returning a C99boolto Rust via the FFI?.
– Shepmaster
Nov 13 '18 at 21:32
add a comment |
The Rust documentation is vague on bool's size.
Is it guaranteed to be 1 byte, or is it unspecified like in C++?
fn main() {
use std::mem;
println!("{}",mem::size_of::<bool>()); //always 1?
}
size rust primitive-types
edited Jun 27 '16 at 13:53
Shepmaster
150k13291430
asked Jun 27 '16 at 6:26
Trevor HickeyTrevor Hickey
16.7k1393187
The Rust documentation is vague on bool's size.
Is it guaranteed to be 1 byte, or is it unspecified like in C++?
fn main() {
use std::mem;
println!("{}",mem::size_of::<bool>()); //always 1?
}
size rust primitive-types
size rust primitive-types
edited Jun 27 '16 at 13:53
Shepmaster
150k13291430
asked Jun 27 '16 at 6:26
Trevor HickeyTrevor Hickey
16.7k1393187
edited Jun 27 '16 at 13:53
Shepmaster
150k13291430
asked Jun 27 '16 at 6:26
Trevor HickeyTrevor Hickey
16.7k1393187
edited Jun 27 '16 at 13:53
Shepmaster
150k13291430
edited Jun 27 '16 at 13:53
Shepmaster
150k13291430
edited Jun 27 '16 at 13:53
Shepmaster
150k13291430
150k13291430
asked Jun 27 '16 at 6:26
Trevor HickeyTrevor Hickey
16.7k1393187
asked Jun 27 '16 at 6:26
Trevor HickeyTrevor Hickey
16.7k1393187
asked Jun 27 '16 at 6:26
Trevor HickeyTrevor Hickey
16.7k1393187
16.7k1393187
1
This is related to stackoverflow.com/q/36924530/5189607
– malbarbo
Jul 1 '16 at 22:04
See also What is the correct type for returning a C99boolto Rust via the FFI?.
– Shepmaster
Nov 13 '18 at 21:32
add a comment |
1
This is related to stackoverflow.com/q/36924530/5189607
– malbarbo
Jul 1 '16 at 22:04
See also What is the correct type for returning a C99boolto Rust via the FFI?.
– Shepmaster
Nov 13 '18 at 21:32
1
1
This is related to stackoverflow.com/q/36924530/5189607
– malbarbo
Jul 1 '16 at 22:04
This is related to stackoverflow.com/q/36924530/5189607
– malbarbo
Jul 1 '16 at 22:04
See also What is the correct type for returning a C99
bool to Rust via the FFI?.– Shepmaster
Nov 13 '18 at 21:32
See also What is the correct type for returning a C99
bool to Rust via the FFI?.– Shepmaster
Nov 13 '18 at 21:32
add a comment |
2 Answers
2
active
oldest
votes
Rust emits i1 to LLVM for bool and relies on whatever it produces. LLVM uses i8 (one byte) to represent i1 in memory for all the platforms supported by Rust for now. On the other hand, there's no certainty about the future, since the Rust developers have been refusing to commit to the particular bool representation so far.
So, it's guaranteed by the current implementation but not guaranteed by any specifications.
You can find more details in this RFC discussion and the linked PR and issue.
answered Jun 27 '16 at 8:15
Andrew LyginAndrew Lygin
4,79812131
In particular this comment which explicitly states that they don't want to tie down the representation.
– Chris Emerson
Jun 27 '16 at 8:56
add a comment |
While historically there was a wish to avoid committing to a more specific representation, it was eventually decided in January 2018 that bool should provide the following guarantees:
- The definition of
boolis equivalent to the C99 definition ofBool_
- For all currently supported platforms, the size of
boolis exactly 1.
The documentation has been updated accordingly. In the Rust reference, bool is defined as thus:
The
booltype is a datatype which can be eithertrueorfalse. The boolean type uses one byte of memory. [...]
It has also been documented since 1.25.0 that the output of std::mem::size_of::<bool>() is 1.
As such, one can indeed rely on bool being 1 byte (and if this is ever to change, it will be a pretty loud one).
edited Nov 13 '18 at 21:31
Shepmaster
150k13291430
answered Nov 13 '18 at 17:33
E_net4 wishes happy holidaysE_net4 wishes happy holidays
12.1k63468
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
Rust emits i1 to LLVM for bool and relies on whatever it produces. LLVM uses i8 (one byte) to represent i1 in memory for all the platforms supported by Rust for now. On the other hand, there's no certainty about the future, since the Rust developers have been refusing to commit to the particular bool representation so far.
So, it's guaranteed by the current implementation but not guaranteed by any specifications.
You can find more details in this RFC discussion and the linked PR and issue.
answered Jun 27 '16 at 8:15
Andrew LyginAndrew Lygin
4,79812131
In particular this comment which explicitly states that they don't want to tie down the representation.
– Chris Emerson
Jun 27 '16 at 8:56
add a comment |
Rust emits i1 to LLVM for bool and relies on whatever it produces. LLVM uses i8 (one byte) to represent i1 in memory for all the platforms supported by Rust for now. On the other hand, there's no certainty about the future, since the Rust developers have been refusing to commit to the particular bool representation so far.
So, it's guaranteed by the current implementation but not guaranteed by any specifications.
You can find more details in this RFC discussion and the linked PR and issue.
answered Jun 27 '16 at 8:15
Andrew LyginAndrew Lygin
4,79812131
In particular this comment which explicitly states that they don't want to tie down the representation.
– Chris Emerson
Jun 27 '16 at 8:56
add a comment |
Rust emits i1 to LLVM for bool and relies on whatever it produces. LLVM uses i8 (one byte) to represent i1 in memory for all the platforms supported by Rust for now. On the other hand, there's no certainty about the future, since the Rust developers have been refusing to commit to the particular bool representation so far.
So, it's guaranteed by the current implementation but not guaranteed by any specifications.
You can find more details in this RFC discussion and the linked PR and issue.
answered Jun 27 '16 at 8:15
Andrew LyginAndrew Lygin
4,79812131
Rust emits i1 to LLVM for bool and relies on whatever it produces. LLVM uses i8 (one byte) to represent i1 in memory for all the platforms supported by Rust for now. On the other hand, there's no certainty about the future, since the Rust developers have been refusing to commit to the particular bool representation so far.
So, it's guaranteed by the current implementation but not guaranteed by any specifications.
You can find more details in this RFC discussion and the linked PR and issue.
answered Jun 27 '16 at 8:15
Andrew LyginAndrew Lygin
4,79812131
edited Jul 1 '16 at 21:22
answered Jun 27 '16 at 8:15
Andrew LyginAndrew Lygin
4,79812131
answered Jun 27 '16 at 8:15
Andrew LyginAndrew Lygin
4,79812131
answered Jun 27 '16 at 8:15
Andrew LyginAndrew Lygin
4,79812131
4,79812131
In particular this comment which explicitly states that they don't want to tie down the representation.
– Chris Emerson
Jun 27 '16 at 8:56
add a comment |
In particular this comment which explicitly states that they don't want to tie down the representation.
– Chris Emerson
Jun 27 '16 at 8:56
In particular this comment which explicitly states that they don't want to tie down the representation.
– Chris Emerson
Jun 27 '16 at 8:56
In particular this comment which explicitly states that they don't want to tie down the representation.
– Chris Emerson
Jun 27 '16 at 8:56
add a comment |
While historically there was a wish to avoid committing to a more specific representation, it was eventually decided in January 2018 that bool should provide the following guarantees:
- The definition of
boolis equivalent to the C99 definition ofBool_
- For all currently supported platforms, the size of
boolis exactly 1.
The documentation has been updated accordingly. In the Rust reference, bool is defined as thus:
The
booltype is a datatype which can be eithertrueorfalse. The boolean type uses one byte of memory. [...]
It has also been documented since 1.25.0 that the output of std::mem::size_of::<bool>() is 1.
As such, one can indeed rely on bool being 1 byte (and if this is ever to change, it will be a pretty loud one).
edited Nov 13 '18 at 21:31
Shepmaster
150k13291430
answered Nov 13 '18 at 17:33
E_net4 wishes happy holidaysE_net4 wishes happy holidays
12.1k63468
add a comment |
While historically there was a wish to avoid committing to a more specific representation, it was eventually decided in January 2018 that bool should provide the following guarantees:
- The definition of
boolis equivalent to the C99 definition ofBool_
- For all currently supported platforms, the size of
boolis exactly 1.
The documentation has been updated accordingly. In the Rust reference, bool is defined as thus:
The
booltype is a datatype which can be eithertrueorfalse. The boolean type uses one byte of memory. [...]
It has also been documented since 1.25.0 that the output of std::mem::size_of::<bool>() is 1.
As such, one can indeed rely on bool being 1 byte (and if this is ever to change, it will be a pretty loud one).
edited Nov 13 '18 at 21:31
Shepmaster
150k13291430
answered Nov 13 '18 at 17:33
E_net4 wishes happy holidaysE_net4 wishes happy holidays
12.1k63468
add a comment |
While historically there was a wish to avoid committing to a more specific representation, it was eventually decided in January 2018 that bool should provide the following guarantees:
- The definition of
boolis equivalent to the C99 definition ofBool_
- For all currently supported platforms, the size of
boolis exactly 1.
The documentation has been updated accordingly. In the Rust reference, bool is defined as thus:
The
booltype is a datatype which can be eithertrueorfalse. The boolean type uses one byte of memory. [...]
It has also been documented since 1.25.0 that the output of std::mem::size_of::<bool>() is 1.
As such, one can indeed rely on bool being 1 byte (and if this is ever to change, it will be a pretty loud one).
edited Nov 13 '18 at 21:31
Shepmaster
150k13291430
answered Nov 13 '18 at 17:33
E_net4 wishes happy holidaysE_net4 wishes happy holidays
12.1k63468
While historically there was a wish to avoid committing to a more specific representation, it was eventually decided in January 2018 that bool should provide the following guarantees:
- The definition of
boolis equivalent to the C99 definition ofBool_
- For all currently supported platforms, the size of
boolis exactly 1.
The documentation has been updated accordingly. In the Rust reference, bool is defined as thus:
The
booltype is a datatype which can be eithertrueorfalse. The boolean type uses one byte of memory. [...]
It has also been documented since 1.25.0 that the output of std::mem::size_of::<bool>() is 1.
As such, one can indeed rely on bool being 1 byte (and if this is ever to change, it will be a pretty loud one).
edited Nov 13 '18 at 21:31
Shepmaster
150k13291430
answered Nov 13 '18 at 17:33
E_net4 wishes happy holidaysE_net4 wishes happy holidays
12.1k63468
edited Nov 13 '18 at 21:31
Shepmaster
150k13291430
edited Nov 13 '18 at 21:31
Shepmaster
150k13291430
edited Nov 13 '18 at 21:31
Shepmaster
150k13291430
150k13291430
answered Nov 13 '18 at 17:33
E_net4 wishes happy holidaysE_net4 wishes happy holidays
12.1k63468
answered Nov 13 '18 at 17:33
E_net4 wishes happy holidaysE_net4 wishes happy holidays
12.1k63468
answered Nov 13 '18 at 17:33
E_net4 wishes happy holidaysE_net4 wishes happy holidays
12.1k63468
12.1k63468
add a comment |
add a comment |
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1
This is related to stackoverflow.com/q/36924530/5189607
– malbarbo
Jul 1 '16 at 22:04
See also What is the correct type for returning a C99
boolto Rust via the FFI?.– Shepmaster
Nov 13 '18 at 21:32