Add linkage attributes to extern "C" blocks

Author: saethlin

build.rs

@@ -193,6 +193,7 @@ fn build_avx512_c_intrinsics() {
     // This is required on 32-bit x86 targets, since the assembly
     // implementation doesn't support those.
     println!("cargo:rustc-cfg=blake3_avx512_ffi");
+    println!("cargo:rustc-cfg=blake3_avx512_ffi_intrinsics");
     let mut build = new_build();
     build.file("c/blake3_avx512.c");
     if is_windows_msvc() {
@@ -213,6 +214,7 @@ fn build_avx512_assembly() {
     // only supports x86_64.
     assert!(is_x86_64());
     println!("cargo:rustc-cfg=blake3_avx512_ffi");
+    println!("cargo:rustc-cfg=blake3_avx512_ffi_assembly");
     let mut build = new_build();
     if is_windows_msvc() {
         build.file("c/blake3_avx512_x86-64_windows_msvc.asm");
@@ -234,6 +236,7 @@ fn build_avx512_assembly() {
 }
 
 fn build_neon_c_intrinsics() {
+    println!("cargo:rustc-cfg=blake3_neon_ffi");
     let mut build = new_build();
     // Note that blake3_neon.c normally depends on the blake3_portable.c
     // for the single-instance compression function, but we expose
@@ -258,7 +261,9 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         "blake3_avx2_ffi",
         "blake3_avx2_rust",
         "blake3_avx512_ffi",
-        "blake3_neon",
+        "blake3_avx512_ffi_assembly",
+        "blake3_avx512_ffi_intrinsics",
+        "blake3_neon_ffi",
     ];
     for cfg_name in all_cfgs {
         // TODO: Switch this whole file to the new :: syntax when our MSRV reaches 1.77.
@@ -300,7 +305,6 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
     if (is_arm() && is_neon())
         || (!is_no_neon() && !is_pure() && is_aarch64() && is_little_endian())
     {
-        println!("cargo:rustc-cfg=blake3_neon");
         build_neon_c_intrinsics();
     }
 

src/ffi_avx2.rs

@@ -33,6 +33,10 @@ pub unsafe fn hash_many<const N: usize>(
 }
 
 pub mod ffi {
+    #[cfg_attr(
+        blake3_avx2_ffi,
+        link(name = "blake3_sse2_sse41_avx2_assembly", kind = "static")
+    )]
     extern "C" {
         pub fn blake3_hash_many_avx2(
             inputs: *const *const u8,

src/ffi_avx512.rs

@@ -83,6 +83,14 @@ pub unsafe fn xof_many(
 }
 
 pub mod ffi {
+    #[cfg_attr(
+        blake3_avx512_ffi_assembly,
+        link(name = "blake3_avx512_assembly", kind = "static")
+    )]
+    #[cfg_attr(
+        blake3_avx512_ffi_intrinsics,
+        link(name = "blake3_avx512_intrinsics", kind = "static")
+    )]
     extern "C" {
         pub fn blake3_compress_in_place_avx512(
             cv: *mut u32,

src/ffi_neon.rs

@@ -53,6 +53,7 @@ pub extern "C" fn blake3_compress_in_place_portable(
 }
 
 pub mod ffi {
+    #[cfg_attr(blake3_neon_ffi, link(name = "blake3_neon", kind = "static"))]
     extern "C" {
         pub fn blake3_hash_many_neon(
             inputs: *const *const u8,

src/ffi_sse2.rs

@@ -61,6 +61,10 @@ pub unsafe fn hash_many<const N: usize>(
 }
 
 pub mod ffi {
+    #[cfg_attr(
+        blake3_sse2_ffi,
+        link(name = "blake3_sse2_sse41_avx2_assembly", kind = "static")
+    )]
     extern "C" {
         pub fn blake3_compress_in_place_sse2(
             cv: *mut u32,

src/ffi_sse41.rs

@@ -61,6 +61,10 @@ pub unsafe fn hash_many<const N: usize>(
 }
 
 pub mod ffi {
+    #[cfg_attr(
+        blake3_sse41_ffi,
+        link(name = "blake3_sse2_sse41_avx2_assembly", kind = "static")
+    )]
     extern "C" {
         pub fn blake3_compress_in_place_sse41(
             cv: *mut u32,

src/lib.rs

@@ -110,7 +110,7 @@ mod avx2;
 #[cfg(blake3_avx512_ffi)]
 #[path = "ffi_avx512.rs"]
 mod avx512;
-#[cfg(blake3_neon)]
+#[cfg(blake3_neon_ffi)]
 #[path = "ffi_neon.rs"]
 mod neon;
 mod portable;

src/platform.rs

@@ -10,7 +10,7 @@ cfg_if::cfg_if! {
                 pub const MAX_SIMD_DEGREE: usize = 8;
             }
         }
-    } else if #[cfg(blake3_neon)] {
+    } else if #[cfg(blake3_neon_ffi)] {
         pub const MAX_SIMD_DEGREE: usize = 4;
     } else {
         pub const MAX_SIMD_DEGREE: usize = 1;
@@ -30,7 +30,7 @@ cfg_if::cfg_if! {
                 pub const MAX_SIMD_DEGREE_OR_2: usize = 8;
             }
         }
-    } else if #[cfg(blake3_neon)] {
+    } else if #[cfg(blake3_neon_ffi)] {
         pub const MAX_SIMD_DEGREE_OR_2: usize = 4;
     } else {
         pub const MAX_SIMD_DEGREE_OR_2: usize = 2;
@@ -49,7 +49,7 @@ pub enum Platform {
     #[cfg(blake3_avx512_ffi)]
     #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
     AVX512,
-    #[cfg(blake3_neon)]
+    #[cfg(blake3_neon_ffi)]
     NEON,
 }
 
@@ -81,7 +81,7 @@ impl Platform {
         }
         // We don't use dynamic feature detection for NEON. If the "neon"
         // feature is on, NEON is assumed to be supported.
-        #[cfg(blake3_neon)]
+        #[cfg(blake3_neon_ffi)]
         {
             return Platform::NEON;
         }
@@ -100,7 +100,7 @@ impl Platform {
             #[cfg(blake3_avx512_ffi)]
             #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
             Platform::AVX512 => 16,
-            #[cfg(blake3_neon)]
+            #[cfg(blake3_neon_ffi)]
             Platform::NEON => 4,
         };
         debug_assert!(degree <= MAX_SIMD_DEGREE);
@@ -134,7 +134,7 @@ impl Platform {
                 crate::avx512::compress_in_place(cv, block, block_len, counter, flags)
             },
             // No NEON compress_in_place() implementation yet.
-            #[cfg(blake3_neon)]
+            #[cfg(blake3_neon_ffi)]
             Platform::NEON => portable::compress_in_place(cv, block, block_len, counter, flags),
         }
     }
@@ -166,7 +166,7 @@ impl Platform {
                 crate::avx512::compress_xof(cv, block, block_len, counter, flags)
             },
             // No NEON compress_xof() implementation yet.
-            #[cfg(blake3_neon)]
+            #[cfg(blake3_neon_ffi)]
             Platform::NEON => portable::compress_xof(cv, block, block_len, counter, flags),
         }
     }
@@ -261,7 +261,7 @@ impl Platform {
                 )
             },
             // Assumed to be safe if the "neon" feature is on.
-            #[cfg(blake3_neon)]
+            #[cfg(blake3_neon_ffi)]
             Platform::NEON => unsafe {
                 crate::neon::hash_many(
                     inputs,
@@ -355,7 +355,7 @@ impl Platform {
         }
     }
 
-    #[cfg(blake3_neon)]
+    #[cfg(blake3_neon_ffi)]
     pub fn neon() -> Option<Self> {
         // Assumed to be safe if the "neon" feature is on.
         Some(Self::NEON)