Zig guarantees the memory layout of f16, f32, f64, f80, and f128 which
means for generic function purposes, values of these types need to be
compared on the basis of their bits in memory. This means nan-packing
can be used with generic functions, for example.
For comptime_float, the sign is observable, whether it is nan is
observable, but not any more kinds of bit patterns are observable.
This fixes the std.fmt tests that check printing "-nan".
Rather than lowering float negation as `0.0 - x`.
* Add AIR instruction for float negation.
* Add compiler-rt functions for f128, f80 negation
closes#11853
The LLVM backend was calculating the amount of padding solely based
on the payload size. However, in the case where there is no union
tag, this fails to take into account alignment.
Closes#11857
Many of the Managed methods accepted by-val parameters which could
reference Limb slices that became invalid memory after any
ensureCapacity calls. Now, Managed methods accept `*const Managed`
parameters so that if the function allows aliasing and the
ensure-capacity call resizes the Limb slice, it also affects the
aliased parameters, avoiding use-after-free bugs.
This is a breaking change that reduces the requirement for callsites to
manually make the ensure-capacity changes prior to calling many of the
Managed methods.
Closes#11897
std.crypto.ecc: add support for the secp256k1 curve
Usage of the secp256k1 elliptic curve recently grew exponentially,
since this is the curve used by Bitcoin and other popular blockchains
such as Ethereum.
With this, Zig has support for all the widely deployed elliptic curves
today.
* mem: refactor tests of split()
- add a few cases for .rest()
- use expectEqualSlices()
* mem: add splitBackwards
Over the last couple of weeks weeks I needed to iterate over a
collection backwards at least twice. Do we want to have this in stdlib?
If yes, click "Merge" and start using today! Free shipping and returns
(before 1.0).
Why is this useful?
-------------------
I need this for building an error wrapper: errors are added in the
wrapper from "lowest" level to "highest" level, and then printed in
reverse order. Imagine `UpdateUsers` call, which needs to return
`error.InvalidInput` and a wrappable error context. In Go we would add a
context to the error when returning it:
// if update_user fails, add context on which user we are operating
if err := update_user(user); err != nil {
return fmt.Errorf("user id=%d: %w", user.id, err)
}
Since Zig cannot pass anything else than u16 with an error (#2647), I
will pass a `err_ctx: *Err`, to the callers, where they can, besides
returning an error, augment it with auxiliary data. `Err` is a
preallocated array that can add zero-byte-separated strings. For a
concrete example, imagine such a call graph:
update_user(User, *Err) error{InvalidInput}!<...>
validate_user([]const u8, *Err) error{InvalidInput}!<...>
Where `validate_user` would like, besides only the error, signal the
invalid field. And `update_user`, besides the error, would signal the
offending user id.
We also don't want the low-level functions to know in which context they
are operating to construct a meaningful error message: if validation
fails, they append their "context" to the buffer. To translate/augment
the Go example above:
pub fn validate_user(err_ctx: *Err, user: User) error{InvalidInput}!void {
const name = user.name;
if (!ascii.isAlpha(name)) {
err_ctx.print("name '{s}' must be ascii-letters only", .{name});
return error.InvalidInput;
}
<...>
}
// update_user validates each user and does something with it.
pub fn update_user(err_ctx: *Err, user: User) error{InvalidInput}!void {
// validate the user before updating it
validate_user(user) catch {
err_ctx.print("user id={d}", .{user.id});
return error.InvalidInput;
};
<...>
}
Then the top-level function (in my case, CLI) will read the buffer
backwards (splitting on `"\x00"`) and print:
user id=123: name 'Žvangalas' must be ascii-letters only
To read that buffer backwards, dear readers of this commit message, I
need `mem.splitBackwards`.
For 25519, it's very likely that applications would ever need the
serialized representation. Expose the value as an integer as in
other curves. Rename the internal representation from `field_size`
to `field_order` for consistency.
Also fix a common typo in `scalar.sub()`.
This reverts commit 8bf3e1f8d0902abd4133e2729b3625c25011c3ff, which
introduced miscompilations for peer expressions any time they needed
coercions to runtime types.
I opened #11957 as a proposal to accomplish the goal of the reverted
commit.
Closes#11898
