Add a C naming option (#2045)

Closes #2045.
Fixes #1252.

5 files changed, 158 insertions, 1 deletions

diff --git a/src/ir/item.rs b/src/ir/item.rs
index ffb52664..9375c798 100644
--- a/src/ir/item.rs
+++ b/src/ir/item.rs
@@ -4,7 +4,7 @@ use super::super::codegen::{EnumVariation, CONSTIFIED_ENUM_MODULE_REPR_NAME};
 use super::analysis::{HasVtable, HasVtableResult, Sizedness, SizednessResult};
 use super::annotations::Annotations;
 use super::comment;
-use super::comp::MethodKind;
+use super::comp::{CompKind, MethodKind};
 use super::context::{BindgenContext, ItemId, PartialType, TypeId};
 use super::derive::{
     CanDeriveCopy, CanDeriveDebug, CanDeriveDefault, CanDeriveEq,
@@ -904,6 +904,12 @@ impl Item {
             names.push(base_name);
         }
 
+        if ctx.options().c_naming {
+            if let Some(prefix) = self.c_naming_prefix() {
+                names.insert(0, prefix.to_string());
+            }
+        }
+
         let name = names.join("_");
 
         let name = if opt.user_mangled == UserMangled::Yes {
@@ -1054,6 +1060,22 @@ impl Item {
         path.reverse();
         path
     }
+
+    /// Returns a prefix for the canonical name when C naming is enabled.
+    fn c_naming_prefix(&self) -> Option<&str> {
+        if let ItemKind::Type(typ) = &self.kind {
+            match typ.kind() {
+                TypeKind::Comp(comp_info) => match comp_info.kind() {
+                    CompKind::Struct => Some("struct"),
+                    CompKind::Union => Some("union"),
+                },
+                TypeKind::Enum(_) => Some("enum"),
+                _ => None,
+            }
+        } else {
+            None
+        }
+    }
 }
 
 impl<T> IsOpaque for T
diff --git a/src/lib.rs b/src/lib.rs
index 58c99c8d..1ac053b7 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -558,6 +558,10 @@ impl Builder {
             output_vector.push("--translate-enum-integer-types".into());
         }
 
+        if self.options.c_naming {
+            output_vector.push("--c-naming".into());
+        }
+
         // Add clang arguments
 
         output_vector.push("--".into());
@@ -1616,6 +1620,15 @@ impl Builder {
         self.options.translate_enum_integer_types = doit;
         self
     }
+
+    /// Generate types with C style naming.
+    ///
+    /// This will add prefixes to the generated type names. For example instead of a struct `A` we
+    /// will generate struct `struct_A`. Currently applies to structs, unions, and enums.
+    pub fn c_naming(mut self, doit: bool) -> Self {
+        self.options.c_naming = doit;
+        self
+    }
 }
 
 /// Configuration options for generated bindings.
@@ -1921,6 +1934,9 @@ struct BindgenOptions {
 
     /// Always translate enum integer types to native Rust integer types.
     translate_enum_integer_types: bool,
+
+    /// Generate types with C style naming.
+    c_naming: bool,
 }
 
 /// TODO(emilio): This is sort of a lie (see the error message that results from
@@ -2062,6 +2078,7 @@ impl Default for BindgenOptions {
             dynamic_link_require_all: false,
             respect_cxx_access_specs: false,
             translate_enum_integer_types: false,
+            c_naming: false,
         }
     }
 }
diff --git a/src/options.rs b/src/options.rs
index ff2d4282..cbdc945e 100644
--- a/src/options.rs
+++ b/src/options.rs
@@ -513,6 +513,9 @@ where
             Arg::with_name("translate-enum-integer-types")
                 .long("translate-enum-integer-types")
                 .help("Always translate enum integer types to native Rust integer types."),
+            Arg::with_name("c-naming")
+                .long("c-naming")
+                .help("Generate types with C style naming."),
         ]) // .args()
         .get_matches_from(args);
 
@@ -953,6 +956,10 @@ where
         builder = builder.translate_enum_integer_types(true);
     }
 
+    if matches.is_present("c-naming") {
+        builder = builder.c_naming(true);
+    }
+
     let verbose = matches.is_present("verbose");
 
     Ok((builder, output, verbose))
diff --git a/tests/expectations/tests/c_naming.rs b/tests/expectations/tests/c_naming.rs
new file mode 100644
index 00000000..041e75ea
--- /dev/null
+++ b/tests/expectations/tests/c_naming.rs
@@ -0,0 +1,92 @@
+#![allow(
+    dead_code,
+    non_snake_case,
+    non_camel_case_types,
+    non_upper_case_globals
+)]
+
+#[repr(C)]
+#[derive(Debug, Default, Copy, Clone)]
+pub struct struct_a {
+    pub a: ::std::os::raw::c_int,
+}
+#[test]
+fn bindgen_test_layout_struct_a() {
+    assert_eq!(
+        ::std::mem::size_of::<struct_a>(),
+        4usize,
+        concat!("Size of: ", stringify!(struct_a))
+    );
+    assert_eq!(
+        ::std::mem::align_of::<struct_a>(),
+        4usize,
+        concat!("Alignment of ", stringify!(struct_a))
+    );
+    assert_eq!(
+        unsafe { &(*(::std::ptr::null::<struct_a>())).a as *const _ as usize },
+        0usize,
+        concat!(
+            "Offset of field: ",
+            stringify!(struct_a),
+            "::",
+            stringify!(a)
+        )
+    );
+}
+pub type a = *const struct_a;
+#[repr(C)]
+#[derive(Copy, Clone)]
+pub union union_b {
+    pub a: ::std::os::raw::c_int,
+    pub b: ::std::os::raw::c_int,
+}
+#[test]
+fn bindgen_test_layout_union_b() {
+    assert_eq!(
+        ::std::mem::size_of::<union_b>(),
+        4usize,
+        concat!("Size of: ", stringify!(union_b))
+    );
+    assert_eq!(
+        ::std::mem::align_of::<union_b>(),
+        4usize,
+        concat!("Alignment of ", stringify!(union_b))
+    );
+    assert_eq!(
+        unsafe { &(*(::std::ptr::null::<union_b>())).a as *const _ as usize },
+        0usize,
+        concat!(
+            "Offset of field: ",
+            stringify!(union_b),
+            "::",
+            stringify!(a)
+        )
+    );
+    assert_eq!(
+        unsafe { &(*(::std::ptr::null::<union_b>())).b as *const _ as usize },
+        0usize,
+        concat!(
+            "Offset of field: ",
+            stringify!(union_b),
+            "::",
+            stringify!(b)
+        )
+    );
+}
+impl Default for union_b {
+    fn default() -> Self {
+        unsafe { ::std::mem::zeroed() }
+    }
+}
+pub type b = union_b;
+pub const enum_c_A: enum_c = 0;
+pub type enum_c = ::std::os::raw::c_uint;
+extern "C" {
+    pub fn takes_a(arg: a);
+}
+extern "C" {
+    pub fn takes_b(arg: b);
+}
+extern "C" {
+    pub fn takes_c(arg: enum_c);
+}
diff --git a/tests/headers/c_naming.h b/tests/headers/c_naming.h
new file mode 100644
index 00000000..fd84c271
--- /dev/null
+++ b/tests/headers/c_naming.h
@@ -0,0 +1,19 @@
+// bindgen-flags: --c-naming
+
+typedef const struct a {
+    int a;
+} *a;
+
+union b {
+    int a;
+    int b;
+};
+typedef union b b;
+
+enum c {
+    A,
+};
+
+void takes_a(a arg) {}
+void takes_b(b arg) {}
+void takes_c(enum c arg) {}