Does prost support no_alloc mode? #1253

raora9045 · 2025-03-03T00:33:55Z

raora9045
Mar 3, 2025

prost supports no_std mode but does it also support no alloc mode i.e stack based allocation for bare meta rust?
i see one repo built on prost(https://github.com/dflemstr/femtopb) that support no_std and no_alloc but wondering if prost support this mode or not?

Where is memory getting allocated for the prost::alloc::vec::Vec?

using prost::alloc::vec::Vec;

let mut triangles = Vec::new();

my proto is

message Vector3 {
float x = 1;
float y = 2;
float z = 3;
}

message Triangle {
Vector3 v0 = 1;
Vector3 v1 = 2;
Vector3 v2 = 3;
Vector3 normal = 4;
}

message Mesh {
repeated Triangle triangles = 1;
}

my code

let mut triangles = Vec::new();
let vec0: Option = Some(Vector3 {
x: 1.0,
y: 1.1,
z: 1.2,
..Default::default()
});

let vec1: Option = Some(Vector3 {
x: 1.0,
y: 1.1,
z: 1.2,
..Default::default()
});

let vec2: Option = Some(Vector3 {
x: 1.0,
y: 1.1,
z: 1.2,
..Default::default()
});

let normal: Option = Some(Vector3 {
x: 1.0,
y: 1.1,
z: 1.2,
..Default::default()
});

let triangle = Triangle {
v0: vec0,
v1: vec1,
v2: vec2,
normal,
..Default::default()
};

triangles.push(triangle);

let mesh = Mesh {
triangles,
..Default::default()
}

let mut bytes = [0u8; 256];
let mut buf = &mut bytes[..];
mesh.encode(&mut buf).unwrap();

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Does prost support no_alloc mode? #1253

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raora9045 Mar 3, 2025

my proto is

my code

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raora9045
Mar 3, 2025