Other calling conventions

Cargo.toml

@@ -29,6 +29,7 @@ toml = "0.8.8"
 proc-macro2 = "1.0.60"
 quote = "1"
 heck = "0.4"
+indoc = "2.0.5"
 
 [dependencies.syn]
 version = "2.0.64"

docs.md

@@ -773,6 +773,18 @@ rename_args = "PascalCase"
 # default: "None"
 sort_by = "Name"
 
+# This rule specifies whether calling conventions specified in Rust should be
+# translated and emitted in C-like outputs.
+#
+# For example, `extern "cdecl" fn foo() {}` will be emitted as `void
+# __cbindgen_abi_cdecl foo();` and a compiler-specific definition (for Clang, GCC, ICX,
+# and MSVC) will be emitted at the top of the file defining `__cbindgen_abi_cdecl` to
+# the appropriate form for the compiler in the case of `cdecl`, this is `__cdecl` for
+# Clang, ICX, and MSVC and `__attribute__((cdecl))` for GCC.
+#
+# default: true
+emit_calling_convention = true
+
 [struct]
 # A rule to use to rename struct field names. The renaming assumes the input is
 # the Rust standard snake_case, however it acccepts all the different rename_args

src/bindgen/bindings.rs

@@ -18,6 +18,7 @@ use crate::bindgen::ir::{
 use crate::bindgen::language_backend::{
     CLikeLanguageBackend, CythonLanguageBackend, LanguageBackend,
 };
+use crate::bindgen::predefines::Predefines;
 use crate::bindgen::writer::SourceWriter;
 
 /// A bindings header that can be written.
@@ -28,6 +29,10 @@ pub struct Bindings {
     struct_map: ItemMap<Struct>,
     typedef_map: ItemMap<Typedef>,
     struct_fileds_memo: RefCell<HashMap<BindgenPath, Rc<Vec<String>>>>,
+    /// Raw code that needs to be inserted at the top of the generated bindings, usually
+    /// based on some condition found in the code itself (motivating example being
+    /// defining compiler and platform independent calling conventions)
+    pub predefines: Predefines,
     pub globals: Vec<Static>,
     pub constants: Vec<Constant>,
     pub items: Vec<ItemContainer>,
@@ -46,6 +51,7 @@ impl Bindings {
         struct_map: ItemMap<Struct>,
         typedef_map: ItemMap<Typedef>,
         constants: Vec<Constant>,
+        predefines: Predefines,
         globals: Vec<Static>,
         items: Vec<ItemContainer>,
         functions: Vec<Function>,
@@ -58,6 +64,7 @@ impl Bindings {
             struct_map,
             typedef_map,
             struct_fileds_memo: Default::default(),
+            predefines,
             globals,
             constants,
             items,

src/bindgen/builder.rs

@@ -360,6 +360,7 @@ impl Builder {
                 Default::default(),
                 Default::default(),
                 Default::default(),
+                Default::default(),
                 true,
                 String::new(),
             ));

src/bindgen/cdecl.rs

@@ -11,6 +11,8 @@ use crate::bindgen::language_backend::LanguageBackend;
 use crate::bindgen::writer::{ListType, SourceWriter};
 use crate::bindgen::{Config, Language};
 
+use super::ir::FunctionAbi;
+
 // This code is for translating Rust types into C declarations.
 // See Section 6.7, Declarations, in the C standard for background.
 // http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf
@@ -40,6 +42,7 @@ struct CDecl {
     type_name: String,
     type_generic_args: Vec<GenericArgument>,
     declarators: Vec<CDeclarator>,
+    abi: Option<FunctionAbi>,
     type_ctype: Option<DeclarationType>,
     deprecated: Option<String>,
 }
@@ -51,6 +54,7 @@ impl CDecl {
             type_name: String::new(),
             type_generic_args: Vec::new(),
             declarators: Vec::new(),
+            abi: None,
             type_ctype: None,
             deprecated: None,
         }
@@ -103,6 +107,7 @@ impl CDecl {
             never_return: f.never_return,
         });
         self.deprecated.clone_from(&f.annotations.deprecated);
+        self.abi = Some(f.abi.clone());
         self.build_type(&f.ret, false, config);
     }
 
@@ -267,6 +272,14 @@ impl CDecl {
             }
         }
 
+        if config.language != Language::Cython && config.function.emit_calling_convention {
+            if let Some(ref abi) = self.abi {
+                if let Some(attribute) = abi.as_attribute() {
+                    write!(out, "{} ", attribute);
+                }
+            }
+        }
+
         // Write the identifier
         if let Some(ident) = ident {
             write!(out, "{}", ident);

src/bindgen/config.rs

@@ -430,6 +430,8 @@ pub struct FunctionConfig {
     pub sort_by: Option<SortKey>,
     /// Optional text to output after functions which return `!`.
     pub no_return: Option<String>,
+    /// Whether to emit calling convention attributes for functions which declare them
+    pub emit_calling_convention: bool,
 }
 
 impl Default for FunctionConfig {
@@ -445,6 +447,7 @@ impl Default for FunctionConfig {
             swift_name_macro: None,
             sort_by: None,
             no_return: None,
+            emit_calling_convention: true,
         }
     }
 }