Add sanity checks for wasm32 for size and alignment of types

Author: elichai

secp256k1-sys/src/types.rs

@@ -12,7 +12,7 @@ pub type c_char = i8;
 
 /// This is an exact copy of https://doc.rust-lang.org/core/ffi/enum.c_void.html
 /// It should be Equivalent to C's void type when used as a pointer.
-/// 
+///
 /// We can replace this with `core::ffi::c_void` once we update the rustc version to >=1.30.0.
 #[repr(u8)]
 pub enum c_void {
@@ -40,3 +40,42 @@ mod tests {
         assert_eq!(TypeId::of::<types::c_char>(), TypeId::of::<raw::c_char>());
     }
 }
+
+
+#[doc(hidden)]
+#[cfg(target_arch = "wasm32")]
+pub fn sanity_checks_for_wasm() {
+    use std::mem::{size_of, align_of};
+    extern "C" {
+        pub static WASM32_INT_SIZE: c_uchar;
+        pub static WASM32_INT_ALIGN: c_uchar;
+
+        pub static WASM32_UNSIGNED_INT_SIZE: c_uchar;
+        pub static WASM32_UNSIGNED_INT_ALIGN: c_uchar;
+
+        pub static WASM32_SIZE_T_SIZE: c_uchar;
+        pub static WASM32_SIZE_T_ALIGN: c_uchar;
+
+        pub static WASM32_UNSIGNED_CHAR_SIZE: c_uchar;
+        pub static WASM32_UNSIGNED_CHAR_ALIGN: c_uchar;
+
+        pub static WASM32_PTR_SIZE: c_uchar;
+        pub static WASM32_PTR_ALIGN: c_uchar;
+    }
+    unsafe {
+        assert_eq!(size_of::<c_int>(), WASM32_INT_SIZE as usize);
+        assert_eq!(align_of::<c_int>(), WASM32_INT_ALIGN as usize);
+
+        assert_eq!(size_of::<c_uint>(), WASM32_UNSIGNED_INT_SIZE as usize);
+        assert_eq!(align_of::<c_uint>(), WASM32_UNSIGNED_INT_ALIGN as usize);
+
+        assert_eq!(size_of::<size_t>(), WASM32_SIZE_T_SIZE as usize);
+        assert_eq!(align_of::<size_t>(), WASM32_SIZE_T_ALIGN as usize);
+
+        assert_eq!(size_of::<c_uchar>(), WASM32_UNSIGNED_CHAR_SIZE as usize);
+        assert_eq!(align_of::<c_uchar>(), WASM32_UNSIGNED_CHAR_ALIGN as usize);
+
+        assert_eq!(size_of::<*const ()>(), WASM32_PTR_SIZE as usize);
+        assert_eq!(align_of::<*const ()>(), WASM32_PTR_ALIGN as usize);
+    }
+}

secp256k1-sys/wasm-sysroot/stdio.h

@@ -0,0 +1,17 @@
+#include <stddef.h>
+#define alignof(type) offsetof (struct { char c; type member; }, member)
+
+extern const unsigned char WASM32_INT_SIZE = sizeof(int);
+extern const unsigned char WASM32_INT_ALIGN = alignof(int);
+
+extern const unsigned char WASM32_UNSIGNED_INT_SIZE = sizeof(unsigned int);
+extern const unsigned char WASM32_UNSIGNED_INT_ALIGN = alignof(unsigned int);
+
+extern const unsigned char WASM32_SIZE_T_SIZE = sizeof(size_t);
+extern const unsigned char WASM32_SIZE_T_ALIGN = alignof(size_t);
+
+extern const unsigned char WASM32_UNSIGNED_CHAR_SIZE = sizeof(unsigned char);
+extern const unsigned char WASM32_UNSIGNED_CHAR_ALIGN = alignof(unsigned char);
+
+extern const unsigned char WASM32_PTR_SIZE = sizeof(void*);
+extern const unsigned char WASM32_PTR_ALIGN = alignof(void*);

src/context.rs

@@ -106,6 +106,9 @@ mod std_only {
     impl<C: Context> Secp256k1<C> {
         /// Lets you create a context in a generic manner(sign/verify/all)
         pub fn gen_new() -> Secp256k1<C> {
+            #[cfg(target_arch = "wasm32")]
+            ffi::types::sanity_checks_for_wasm();
+
             let buf = vec![0u8; Self::preallocate_size_gen()].into_boxed_slice();
             let ptr = Box::into_raw(buf);
             Secp256k1 {
@@ -192,6 +195,9 @@ unsafe impl<'buf> Context for AllPreallocated<'buf> {
 impl<'buf, C: Context + 'buf> Secp256k1<C> {
     /// Lets you create a context with preallocated buffer in a generic manner(sign/verify/all)
     pub fn preallocated_gen_new(buf: &'buf mut [u8]) -> Result<Secp256k1<C>, Error> {
+        #[cfg(target_arch = "wasm32")]
+        ffi::types::sanity_checks_for_wasm();
+
         if buf.len() < Self::preallocate_size_gen() {
             return Err(Error::NotEnoughMemory);
         }