Partially support #[cfg]s on fields

src/bindgen/ir/enumeration.rs

@@ -112,6 +112,7 @@ impl EnumVariant {
                             None => i.to_string(),
                         },
                         ty,
+                        cfg: Cfg::load(&field.attrs),
                         annotations: AnnotationSet::load(&field.attrs)?,
                         documentation: Documentation::load(&field.attrs),
                     });

src/bindgen/ir/field.rs

@@ -2,13 +2,15 @@ use std::io::Write;
 
 use crate::bindgen::cdecl;
 use crate::bindgen::config::{Config, Language};
-use crate::bindgen::ir::{AnnotationSet, Documentation, Path, Type};
+use crate::bindgen::ir::{AnnotationSet, Cfg, ConditionWrite};
+use crate::bindgen::ir::{Documentation, Path, ToCondition, Type};
 use crate::bindgen::writer::{Source, SourceWriter};
 
 #[derive(Debug, Clone)]
 pub struct Field {
     pub name: String,
     pub ty: Type,
+    pub cfg: Option<Cfg>,
     pub annotations: AnnotationSet,
     pub documentation: Documentation,
 }
@@ -18,6 +20,7 @@ impl Field {
         Field {
             name,
             ty,
+            cfg: None,
             annotations: AnnotationSet::new(),
             documentation: Documentation::none(),
         }
@@ -33,6 +36,7 @@ impl Field {
                     .ok_or_else(|| "field is missing identifier".to_string())?
                     .to_string(),
                 ty,
+                cfg: Cfg::load(&field.attrs),
                 annotations: AnnotationSet::load(&field.attrs)?,
                 documentation: Documentation::load(&field.attrs),
             })
@@ -44,6 +48,12 @@ impl Field {
 
 impl Source for Field {
     fn write<F: Write>(&self, config: &Config, out: &mut SourceWriter<F>) {
+        // Cython doesn't support conditional fields.
+        let condition = self.cfg.to_condition(config);
+        if config.language != Language::Cython {
+            condition.write_before(config, out);
+        }
+
         self.documentation.write(config, out);
         cdecl::write_field(out, &self.ty, &self.name, config);
         // Cython extern declarations don't manage layouts, layouts are defined entierly by the
@@ -53,5 +63,15 @@ impl Source for Field {
                 write!(out, ": {}", bitfield.unwrap_or_default());
             }
         }
+
+        if config.language != Language::Cython {
+            condition.write_after(config, out);
+            // FIXME(#634): `write_vertical_source_list` should support
+            // configuring list elements natively. For now we print a newline
+            // here to avoid printing `#endif;` with semicolon.
+            if condition.is_some() {
+                out.new_line();
+            }
+        }
     }
 }

src/bindgen/ir/structure.rs

@@ -88,6 +88,7 @@ impl Struct {
                         out.push(Field {
                             name: format!("{}", current),
                             ty,
+                            cfg: Cfg::load(&field.attrs),
                             annotations: AnnotationSet::load(&field.attrs)?,
                             documentation: Documentation::load(&field.attrs),
                         });
@@ -191,6 +192,7 @@ impl Struct {
                 .map(|field| Field {
                     name: field.name.clone(),
                     ty: field.ty.specialize(mappings),
+                    cfg: field.cfg.clone(),
                     annotations: field.annotations.clone(),
                     documentation: field.documentation.clone(),
                 })

src/bindgen/ir/union.rs

@@ -180,6 +180,7 @@ impl Item for Union {
                     overriden_fields.push(Field {
                         name: o[i].clone(),
                         ty: field.ty.clone(),
+                        cfg: field.cfg.clone(),
                         annotations: field.annotations.clone(),
                         documentation: field.documentation.clone(),
                     });
@@ -196,6 +197,7 @@ impl Item for Union {
                         .apply(&field.name, IdentifierType::StructMember)
                         .into_owned(),
                     ty: field.ty.clone(),
+                    cfg: field.cfg.clone(),
                     annotations: field.annotations.clone(),
                     documentation: field.documentation.clone(),
                 })
@@ -256,6 +258,7 @@ impl Item for Union {
                 .map(|field| Field {
                     name: field.name.clone(),
                     ty: field.ty.specialize(&mappings),
+                    cfg: field.cfg.clone(),
                     annotations: field.annotations.clone(),
                     documentation: field.documentation.clone(),
                 })

tests/expectations/cfg.both.c

@@ -71,6 +71,13 @@ typedef struct BarHandle {
 } BarHandle;
 #endif
 
+typedef struct ConditionalField {
+#if defined(X11)
+  int32_t field
+#endif
+  ;
+} ConditionalField;
+
 #if (defined(PLATFORM_UNIX) && defined(X11))
 void root(struct FooHandle a, union C c);
 #endif
@@ -78,3 +85,5 @@ void root(struct FooHandle a, union C c);
 #if (defined(PLATFORM_WIN) || defined(M_32))
 void root(struct BarHandle a, union C c);
 #endif
+
+void cond(struct ConditionalField a);

tests/expectations/cfg.both.compat.c

@@ -89,6 +89,13 @@ typedef struct BarHandle {
 } BarHandle;
 #endif
 
+typedef struct ConditionalField {
+#if defined(X11)
+  int32_t field
+#endif
+  ;
+} ConditionalField;
+
 #ifdef __cplusplus
 extern "C" {
 #endif // __cplusplus
@@ -101,6 +108,8 @@ void root(struct FooHandle a, union C c);
 void root(struct BarHandle a, union C c);
 #endif
 
+void cond(struct ConditionalField a);
+
 #ifdef __cplusplus
 } // extern "C"
 #endif // __cplusplus

tests/expectations/cfg.c

@@ -71,6 +71,13 @@ typedef struct {
 } BarHandle;
 #endif
 
+typedef struct {
+#if defined(X11)
+  int32_t field
+#endif
+  ;
+} ConditionalField;
+
 #if (defined(PLATFORM_UNIX) && defined(X11))
 void root(FooHandle a, C c);
 #endif
@@ -78,3 +85,5 @@ void root(FooHandle a, C c);
 #if (defined(PLATFORM_WIN) || defined(M_32))
 void root(BarHandle a, C c);
 #endif
+
+void cond(ConditionalField a);

tests/expectations/cfg.compat.c

@@ -89,6 +89,13 @@ typedef struct {
 } BarHandle;
 #endif
 
+typedef struct {
+#if defined(X11)
+  int32_t field
+#endif
+  ;
+} ConditionalField;
+
 #ifdef __cplusplus
 extern "C" {
 #endif // __cplusplus
@@ -101,6 +108,8 @@ void root(FooHandle a, C c);
 void root(BarHandle a, C c);
 #endif
 
+void cond(ConditionalField a);
+
 #ifdef __cplusplus
 } // extern "C"
 #endif // __cplusplus

tests/expectations/cfg.cpp

@@ -195,6 +195,13 @@ struct BarHandle {
 };
 #endif
 
+struct ConditionalField {
+#if defined(X11)
+  int32_t field
+#endif
+  ;
+};
+
 extern "C" {
 
 #if (defined(PLATFORM_UNIX) && defined(X11))
@@ -205,4 +212,6 @@ void root(FooHandle a, C c);
 void root(BarHandle a, C c);
 #endif
 
+void cond(ConditionalField a);
+
 } // extern "C"

tests/expectations/cfg.pyx

@@ -55,8 +55,13 @@ cdef extern from *:
       int32_t x;
       float y;
 
+  ctypedef struct ConditionalField:
+    int32_t field;
+
   IF (PLATFORM_UNIX and X11):
     void root(FooHandle a, C c);
 
   IF (PLATFORM_WIN or M_32):
     void root(BarHandle a, C c);
+
+  void cond(ConditionalField a);

tests/expectations/cfg.tag.c

@@ -71,6 +71,13 @@ struct BarHandle {
 };
 #endif
 
+struct ConditionalField {
+#if defined(X11)
+  int32_t field
+#endif
+  ;
+};
+
 #if (defined(PLATFORM_UNIX) && defined(X11))
 void root(struct FooHandle a, union C c);
 #endif
@@ -78,3 +85,5 @@ void root(struct FooHandle a, union C c);
 #if (defined(PLATFORM_WIN) || defined(M_32))
 void root(struct BarHandle a, union C c);
 #endif
+
+void cond(struct ConditionalField a);

tests/expectations/cfg.tag.compat.c

@@ -89,6 +89,13 @@ struct BarHandle {
 };
 #endif
 
+struct ConditionalField {
+#if defined(X11)
+  int32_t field
+#endif
+  ;
+};
+
 #ifdef __cplusplus
 extern "C" {
 #endif // __cplusplus
@@ -101,6 +108,8 @@ void root(struct FooHandle a, union C c);
 void root(struct BarHandle a, union C c);
 #endif
 
+void cond(struct ConditionalField a);
+
 #ifdef __cplusplus
 } // extern "C"
 #endif // __cplusplus

tests/expectations/cfg.tag.pyx

@@ -55,8 +55,13 @@ cdef extern from *:
       int32_t x;
       float y;
 
+  cdef struct ConditionalField:
+    int32_t field;
+
   IF (PLATFORM_UNIX and X11):
     void root(FooHandle a, C c);
 
   IF (PLATFORM_WIN or M_32):
     void root(BarHandle a, C c);
+
+  void cond(ConditionalField a);

tests/rust/cfg.rs

@@ -40,6 +40,15 @@ struct BarHandle {
     y: f32,
 }
 
+// FIXME(#634): Support deriving methods for structs with conditional fields.
+/// cbindgen:derive-eq=false
+/// cbindgen:derive-neq=false
+#[repr(C)]
+struct ConditionalField {
+    #[cfg(x11)]
+    field: i32,
+}
+
 #[cfg(all(unix, x11))]
 #[no_mangle]
 pub extern "C" fn root(a: FooHandle, c: C)
@@ -49,3 +58,7 @@ pub extern "C" fn root(a: FooHandle, c: C)
 #[no_mangle]
 pub extern "C" fn root(a: BarHandle, c: C)
 { }
+
+#[no_mangle]
+pub extern "C" fn cond(a: ConditionalField)
+{ }