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Initial pass at new host ABI #7795

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Merged
merged 14 commits into from
May 19, 2025
Merged

Initial pass at new host ABI #7795

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47286b0
Add host_abi.zig
rtfeldman May 18, 2025
f53d97c
Use explicit env pointer
rtfeldman May 18, 2025
6664b2f
fix typo
rtfeldman May 18, 2025
324c028
Use comptime for RocCall and RocOps
rtfeldman May 18, 2025
be5f68c
Revise doc comment
rtfeldman May 18, 2025
e528bbf
Update some doc comments
rtfeldman May 18, 2025
b7489e7
Add a comment about zig std
rtfeldman May 18, 2025
6cba47b
Use varargs for RocCall
rtfeldman May 18, 2025
e5ffde4
Add HostFns
rtfeldman May 18, 2025
abdbb99
We don't know Ret at comptime
rtfeldman May 18, 2025
609bac1
Rename ret to answer
rtfeldman May 18, 2025
b231752
Make RocRealloc extern
rtfeldman May 19, 2025
1448adb
fix typo
rtfeldman May 19, 2025
d078548
Make some other structs `extern`
rtfeldman May 19, 2025
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Rename ret to answer
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@rtfeldman
rtfeldman committed May 18, 2025
commit 609bac1e41a39edf5b38a4c0b0aabd52effc6215
4 changes: 2 additions & 2 deletions src/host_abi.zig
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Expand Up @@ -68,7 +68,7 @@ pub fn RocOps(comptime CallEnv: type, comptime HostFns: type) type {
pub const RocAlloc = struct {
alignment: usize,
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Not sure if this helps here since the struct has no padding, but in Zig std lib we've started using an Alignment type that stores the log2 value. It's pretty handy because you only need 6 bits to describe any alignment for a 64-bit address.

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Nice, that's a cool trick! I agree that it probably doesn't help here, but that's a good one to know for future reference. 🤘

length: usize,
ret: *anyopaque,
answer: *anyopaque,
};
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@rtfeldman rtfeldman May 18, 2025 •
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This is a bit different from how we're doing it in the Rust compiler. Some notes:

  • To avoid needing to get into the C calling convention at all, I continued using the "all functions take a single pointer and return void" thing with roc_alloc and friends.
    • The one exception is that I have them all take a second argument, the "env pointer" that's a pointer to whatever the host wants it to be - e.g. a pointer to an arena in case the host wants to use arena allocation for everything.
  • Since this is now different enough from the signature for something like malloc, I figured it would be fine to require that the host handle OOM itself rather than the Roc compiler generating an extra conditional to detect null and call roc_crashed if so. (All the hosts that anyone will use as templates to copy from will do this anyway, so I don't think it will be a problem.)


/// When RocOps.roc_dealloc gets called, it will be passed one of these.
Expand All @@ -87,7 +87,7 @@ pub const RocDealloc = struct {
pub const RocRealloc = struct {
alignment: usize,
new_length: usize,
ret: *anyopaque,
answer: *anyopaque,
};

/// The UTF-8 string message the host receives when a Roc program crashes
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