Merge #315

315: Correct C interop declarations r=adamgreig a=JVMerkle Functions with external C linkage have to be wrapped with `extern "C" { ... }`, `extern "C"` as part of the function signature is not sufficient. Resolves #236 Signed-off-by: Julian Merkle <[email protected]> Co-authored-by: Julian Merkle <[email protected]>
rust-embedded · Apr 19, 2022 · 0d73660 · 0d73660
2 parents 12f95ff + c1e7ca0
commit 0d73660
Showing 1 changed file with 8 additions and 6 deletions.
diff --git a/src/interoperability/c-with-rust.md b/src/interoperability/c-with-rust.md
@@ -37,11 +37,13 @@ pub struct CoolStruct {
     pub y: cty::c_int,
 }
 
-pub extern "C" fn cool_function(
-    i: cty::c_int,
-    c: cty::c_char,
-    cs: *mut CoolStruct
-);
+extern "C" {
+    pub fn cool_function(
+        i: cty::c_int,
+        c: cty::c_char,
+        cs: *mut CoolStruct
+    );
+}
 ```
 
 Let's take a look at this definition one piece at a time, to explain each of the parts.
@@ -61,7 +63,7 @@ pub y: cty::c_int,
 Due to the flexibility of how C or C++ defines an `int` or `char`, it is recommended to use primitive data types defined in `cty`, which will map types from C to types in Rust.
 
 ```rust,ignore
-pub extern "C" fn cool_function( ... );
+extern "C" { pub fn cool_function( ... ); }
 ```
 
 This statement defines the signature of a function that uses the C ABI, called `cool_function`. By defining the signature without defining the body of the function, the definition of this function will need to be provided elsewhere, or linked into the final library or binary from a static library.