Remove build.rs.

This was more useful at the time when we were determining, e.g., optimal lookup
table sizes and could regenerate them more easily, but it came at a massive
complexity cost.  It also meant that we were unable to implement backend
autoselection.  This commit removes the `build.rs` entirely.  In the future, a
different `build.rs` could be added that auto-selects a backend, but it seems
like the current default-u64 setup has been working fine.

Cargo.toml

@@ -16,7 +16,6 @@ exclude = [
     ".gitignore",
     ".travis.yml",
 ]
-build = "build.rs"
 
 [package.metadata.docs.rs]
 # Disabled for now since this is borked; tracking https://github.com/rust-lang/docs.rs/issues/302
@@ -37,12 +36,6 @@ rand = "0.6"
 name = "dalek_benchmarks"
 harness = false
 
-# Note: we generate precomputed tables by building the crate twice: once as
-# part of build.rs, and then once "for real".
-#
-# This means that the [dependencies] and [build-dependencies] sections must
-# match exactly, since the build.rs uses the crate itself as a library.
-
 [dependencies]
 rand_core = { version = "0.3.0", default-features = false }
 byteorder = { version = "^1.2.3", default-features = false, features = ["i128"] }
@@ -52,21 +45,11 @@ subtle = { version = "2", default-features = false }
 serde = { version = "1.0", default-features = false, optional = true }
 packed_simd = { version = "0.3.0", features = ["into_bits"], optional = true }
 
-[build-dependencies]
-rand_core = { version = "0.3.0", default-features = false }
-byteorder = { version = "^1.2.3", default-features = false, features = ["i128"] }
-digest = { version = "0.8", default-features = false }
-clear_on_drop = "=0.2.3"
-subtle = { version = "2", default-features = false }
-serde = { version = "1.0", default-features = false, optional = true }
-packed_simd = { version = "0.3.0", features = ["into_bits"], optional = true }
-
 [features]
 nightly = ["subtle/nightly", "clear_on_drop/nightly"]
 default = ["std", "u64_backend"]
 std = ["alloc", "subtle/std", "rand_core/std"]
 alloc = []
-yolocrypto = []
 
 # The u32 backend uses u32s with u64 products.
 u32_backend = []
@@ -74,12 +57,6 @@ u32_backend = []
 u64_backend = []
 # The SIMD backend uses parallel formulas, using either AVX2 or AVX512-IFMA.
 simd_backend = ["nightly", "u64_backend", "packed_simd"]
-# Old name for the SIMD backend, preserved for compatibility
+# DEPRECATED: this is now an alias for `simd_backend` and may be removed
+# in some future release.
 avx2_backend = ["simd_backend"]
-
-# Signals that we're in the main build stage.  This is off by default,
-# to signal stage 1 of the build, where build.rs loads the library
-# into the build script. Then, the build.rs emits the stage2_build
-# feature before the main-stage compilation.
-stage2_build = []
-

build.rs

@@ -1,131 +0,0 @@
-#![cfg_attr(all(feature = "alloc", not(feature = "std")), feature(alloc))]
-#![cfg_attr(feature = "nightly", feature(doc_cfg))]
-#![cfg_attr(feature = "simd_backend", feature(stdsimd))]
-#![allow(unused_variables)]
-#![allow(non_snake_case)]
-#![allow(dead_code)]
-
-#[cfg(all(feature = "alloc", not(feature = "std")))]
-extern crate alloc;
-extern crate byteorder;
-extern crate clear_on_drop;
-extern crate core;
-extern crate digest;
-extern crate rand_core;
-extern crate subtle;
-
-#[cfg(all(feature = "nightly", feature = "packed_simd"))]
-extern crate packed_simd;
-
-use std::env;
-use std::fs::File;
-use std::io::Write;
-use std::path::Path;
-
-// Replicate lib.rs in the build.rs, since we're effectively building the whole crate twice.
-//
-// This should be fixed up by refactoring our code to seperate the "minimal" parts from the rest.
-//
-// For instance, this shouldn't exist here at all, but it does.
-#[cfg(feature = "serde")]
-extern crate serde;
-
-// Macros come first!
-#[path = "src/macros.rs"]
-#[macro_use]
-mod macros;
-
-// Public modules
-
-#[path = "src/constants.rs"]
-mod constants;
-#[path = "src/edwards.rs"]
-mod edwards;
-#[path = "src/montgomery.rs"]
-mod montgomery;
-#[path = "src/ristretto.rs"]
-mod ristretto;
-#[path = "src/scalar.rs"]
-mod scalar;
-#[path = "src/traits.rs"]
-mod traits;
-
-// Internal modules
-
-#[path = "src/backend/mod.rs"]
-mod backend;
-#[path = "src/field.rs"]
-mod field;
-#[path = "src/prelude.rs"]
-mod prelude;
-#[path = "src/window.rs"]
-mod window;
-
-use edwards::EdwardsBasepointTable;
-
-fn main() {
-    // Enable the "stage2_build" feature in the main build stage
-    println!("cargo:rustc-cfg=feature=\"stage2_build\"\n");
-
-    let out_dir = env::var("OUT_DIR").unwrap();
-    let dest_path = Path::new(&out_dir).join("basepoint_table.rs");
-    let mut f = File::create(&dest_path).unwrap();
-
-    // Generate a table of precomputed multiples of the basepoint
-    let table = EdwardsBasepointTable::create(&constants::ED25519_BASEPOINT_POINT);
-
-    f.write_all(
-        format!(
-            "\n
-#[cfg(feature = \"u32_backend\")]
-use backend::serial::u32::field::FieldElement2625;
-
-#[cfg(feature = \"u64_backend\")]
-use backend::serial::u64::field::FieldElement51;
-
-use edwards::EdwardsBasepointTable;
-
-use backend::serial::curve_models::AffineNielsPoint;
-
-use window::LookupTable;
-
-/// Table containing precomputed multiples of the Ed25519 basepoint \\\\(B = (x, 4/5)\\\\).
-pub const ED25519_BASEPOINT_TABLE: EdwardsBasepointTable = ED25519_BASEPOINT_TABLE_INNER_DOC_HIDDEN;
-
-/// Inner constant, used to avoid filling the docs with precomputed points.
-#[doc(hidden)]
-pub const ED25519_BASEPOINT_TABLE_INNER_DOC_HIDDEN: EdwardsBasepointTable = {:?};
-\n\n",
-            &table
-        )
-        .as_bytes(),
-    )
-    .unwrap();
-
-    // Now generate AFFINE_ODD_MULTIPLES_OF_BASEPOINT
-    // if we are going to build the serial scalar_mul backend
-    #[cfg(not(all(
-        feature = "simd_backend",
-        any(target_feature = "avx2", target_feature = "avx512ifma")
-    )))]
-    {
-        use backend::serial::curve_models::AffineNielsPoint;
-        use window::NafLookupTable8;
-
-        let B = &constants::ED25519_BASEPOINT_POINT;
-        let odd_multiples = NafLookupTable8::<AffineNielsPoint>::from(B);
-
-        f.write_all(
-            format!(
-                "\n
-use window::NafLookupTable8;
-/// Odd multiples of the basepoint `[B, 3B, 5B, 7B, 9B, 11B, 13B, 15B, ..., 127B]`.
-pub(crate) const AFFINE_ODD_MULTIPLES_OF_BASEPOINT: NafLookupTable8<AffineNielsPoint> = {:?};
-\n\n",
-                &odd_multiples
-            )
-            .as_bytes(),
-        )
-        .unwrap();
-    }
-}

src/backend/serial/scalar_mul/mod.rs

@@ -18,7 +18,6 @@
 
 pub mod variable_base;
 
-#[cfg(feature = "stage2_build")]
 pub mod vartime_double_base;
 
 #[cfg(feature = "alloc")]

src/backend/vector/avx2/mod.rs

@@ -8,17 +8,8 @@
 // - Isis Agora Lovecruft <isis@patternsinthevoid.net>
 // - Henry de Valence <hdevalence@hdevalence.ca>
 
-// Conditionally include the AVX2 notes if:
-// - we're on nightly (so we can include docs at all)
-// - we're in stage 2 of the build.
-// The latter point prevents a really silly and annoying problem,
-// where the location of ".." is different depending on whether we're
-// building the crate for real, or whether we're in build.rs
-// generating the lookup tables (in which case we're relative to the
-// location of build.rs, not lib.rs, so the markdown file appears
-// missing).
 #![cfg_attr(
-    all(feature = "nightly", feature = "stage2_build"),
+    feature = "nightly",
     doc(include = "../../../../docs/avx2-notes.md")
 )]
 

src/backend/vector/ifma/mod.rs

@@ -8,7 +8,7 @@
 // - Henry de Valence <hdevalence@hdevalence.ca>
 
 #![cfg_attr(
-    all(feature = "nightly", feature = "stage2_build"),
+    feature = "nightly",
     doc(include = "../../../../docs/ifma-notes.md")
 )]
 

src/backend/vector/mod.rs

@@ -8,17 +8,9 @@
 // - Isis Agora Lovecruft <isis@patternsinthevoid.net>
 // - Henry de Valence <hdevalence@hdevalence.ca>
 
-// Conditionally include the notes if:
-// - we're on nightly (so we can include docs at all)
-// - we're in stage 2 of the build.
-// The latter point prevents a really silly and annoying problem,
-// where the location of ".." is different depending on whether we're
-// building the crate for real, or whether we're in build.rs
-// generating the lookup tables (in which case we're relative to the
-// location of build.rs, not lib.rs, so the markdown file appears
-// missing).
+// Conditionally include the notes if we're on nightly (so we can include docs at all).
 #![cfg_attr(
-    all(feature = "nightly", feature = "stage2_build"),
+    feature = "nightly",
     doc(include = "../../../docs/parallel-formulas.md")
 )]
 

src/constants.rs

@@ -83,16 +83,8 @@ pub const BASEPOINT_ORDER: Scalar = Scalar{
     ],
 };
 
-// Precomputed basepoint table is generated into a file by build.rs
-
-#[cfg(feature = "stage2_build")]
-include!(concat!(env!("OUT_DIR"), "/basepoint_table.rs"));
-
-#[cfg(feature = "stage2_build")]
 use ristretto::RistrettoBasepointTable;
-
 /// The Ristretto basepoint, as a `RistrettoBasepointTable` for scalar multiplication.
-#[cfg(feature = "stage2_build")]
 pub const RISTRETTO_BASEPOINT_TABLE: RistrettoBasepointTable
     = RistrettoBasepointTable(ED25519_BASEPOINT_TABLE);
 

src/edwards.rs

@@ -726,7 +726,6 @@ impl VartimePrecomputedMultiscalarMul for VartimeEdwardsPrecomputation {
 
 impl EdwardsPoint {
     /// Compute \\(aA + bB\\) in variable time, where \\(B\\) is the Ed25519 basepoint.
-    #[cfg(feature = "stage2_build")]
     pub fn vartime_double_scalar_mul_basepoint(
         a: &Scalar,
         A: &EdwardsPoint,
@@ -937,7 +936,7 @@ impl Debug for EdwardsBasepointTable {
 // Tests
 // ------------------------------------------------------------------------
 
-#[cfg(all(test, feature = "stage2_build"))]
+#[cfg(test)]
 mod test {
     use field::FieldElement;
     use scalar::Scalar;

src/lib.rs

@@ -45,7 +45,7 @@ extern crate byteorder;
 extern crate clear_on_drop;
 pub extern crate digest;
 extern crate rand_core;
-#[cfg(all(test, feature = "stage2_build"))]
+#[cfg(test)]
 extern crate rand_os;
 
 // Used for traits related to constant-time code.

src/montgomery.rs

@@ -299,7 +299,7 @@ impl<'a, 'b> Mul<&'b MontgomeryPoint> for &'a Scalar {
 // Tests
 // ------------------------------------------------------------------------
 
-#[cfg(all(test, feature = "stage2_build"))]
+#[cfg(test)]
 mod test {
     use constants;
     use super::*;

src/ristretto.rs

@@ -955,7 +955,6 @@ impl VartimePrecomputedMultiscalarMul for VartimeRistrettoPrecomputation {
 impl RistrettoPoint {
     /// Compute \\(aA + bB\\) in variable time, where \\(B\\) is the
     /// Ristretto basepoint.
-    #[cfg(feature = "stage2_build")]
     pub fn vartime_double_scalar_mul_basepoint(
         a: &Scalar,
         A: &RistrettoPoint,
@@ -1073,7 +1072,7 @@ impl Debug for RistrettoPoint {
 // Tests
 // ------------------------------------------------------------------------
 
-#[cfg(all(test, feature = "stage2_build"))]
+#[cfg(test)]
 mod test {
     #[cfg(feature = "rand")]
     use rand_os::OsRng;