Merge pull request #119 from kornilova-l/skip-illegal-scala-functions

Skip functions that pass arrays or structs by value

Author: kornilova203

bindgen/Utils.h

@@ -116,11 +116,14 @@ static inline std::string replaceChar(const std::string &str,
  * @return true if given type is of type T or is an alias for type T.
  */
 template <typename T> static inline bool isAliasForType(Type *type) {
-    if (isInstanceOf<TypeDef>(type)) {
-        auto *typeDef = dynamic_cast<TypeDef *>(type);
+    if (isInstanceOf<T>(type)) {
+        return true;
+    }
+    auto *typeDef = dynamic_cast<TypeDef *>(type);
+    if (typeDef) {
         return isAliasForType<T>(typeDef->getType().get());
     }
-    return isInstanceOf<T>(type);
+    return false;
 }
 
 #endif // UTILS_H

bindgen/ir/Function.cpp

@@ -1,5 +1,6 @@
 #include "Function.h"
 #include "../Utils.h"
+#include "Struct.h"
 
 Parameter::Parameter(std::string name, std::shared_ptr<Type> type)
     : TypeAndName(std::move(name), type) {}
@@ -71,3 +72,19 @@ Function::~Function() {
         delete parameter;
     }
 }
+
+bool Function::isLegalScalaNativeFunction() const {
+    /* Return type and parameters types cannot be array types because array type
+     * in this case is always represented as a pointer to element type */
+    if (isAliasForType<Struct>(retType.get()) ||
+        isAliasForType<Union>(retType.get())) {
+        return false;
+    }
+    for (const auto &parameter : parameters) {
+        if (isAliasForType<Struct>(parameter->getType().get()) ||
+            isAliasForType<Union>(parameter->getType().get())) {
+            return false;
+        }
+    }
+    return true;
+}

bindgen/ir/Function.h

@@ -2,6 +2,7 @@
 #define SCALA_NATIVE_BINDGEN_FUNCTION_H
 
 #include "TypeAndName.h"
+#include "TypeDef.h"
 #include <llvm/Support/raw_ostream.h>
 #include <string>
 #include <vector>
@@ -27,6 +28,12 @@ class Function {
 
     void setScalaName(std::string scalaName);
 
+    /**
+     * @return true if the function does not use values of structs or arrays
+     * (note: unions are represented as arrays)
+     */
+    bool isLegalScalaNativeFunction() const;
+
   private:
     std::string getVarargsParameterName() const;
 

bindgen/ir/IR.cpp

@@ -122,7 +122,15 @@ llvm::raw_ostream &operator<<(llvm::raw_ostream &s, const IR &ir) {
         }
 
         for (const auto &func : ir.functions) {
-            s << *func;
+            if (func->isLegalScalaNativeFunction()) {
+                s << *func;
+            } else {
+                llvm::errs()
+                    << "Warning: Function " << func->getName()
+                    << " is skipped because Scala Native does not support "
+                       "passing structs and arrays by value.\n";
+                llvm::errs().flush();
+            }
         }
 
         s << "}\n\n";

docs/src/paradox/limitations/index.md

@@ -1,35 +1,47 @@
 # Limitations
 
-There are multiple unsupported cases that should be considered when generating bindings:
-
- 1. Currently bindgen does not support passing structs by value.  
-    For example, it will not be possible to call these two functions from Scala Native code:
-    
-    ```c
-    struct MyStruct {
-        int a;
-    };
-    
-    struct MyStruct returnStruct();
-    
-    void handleStruct(struct MyStruct mystr);
-    ```
-    To support such cases one should generate bindings for C wrapper functions that use pointers to structs instead of actual structs.
- 2. `#define`s for literals and variables are supported. For other types of `#define`s,
-    write wrapper functions that return defined values.
-    
-    ```c
-    // Supported
-    #define ESC 0x1b            /* Defines for numerical and string literals. */
-    extern const int pi_const;
-    #define PI pi_const         /* Defines aliasing extern variables. */
-
-    // Not supported (non-exhaustive list)
-    #define COLS      (getenv("COLS") ? atoi(getenv("COLS")) : 80)
-    #define MAX(a, b) (a > b ? a : b)
-    ```
-
- 3. There is no way to reuse already generated bindings.  
-    Bindgen outputs bindings also for headers that were included in a given header. See @github[#2](#2).
- 4. Type qualifiers `const`, `volatile` and `restrict` are not supported.
- 5. Extern variables are read-only. See @github[scala-native/scala-native#202](scala-native/scala-native#202).
+There are multiple unsupported cases that should be considered when generating bindings.
+
+## Passing structs by value
+
+Scala Native does not support passing structs by value, bindgen skips such functions.
+```c
+struct MyStruct {
+    int a;
+};
+
+struct MyStruct returnStruct(); // skipped
+
+void handleStruct(struct MyStruct mystr); // skipped
+```
+To support such cases one should generate bindings for C wrapper functions that use pointers to structs instead of
+actual structs.
+
+## Limited support of `#define`s
+
+`#define`s for literals and variables are supported. For other types of `#define`s,
+write wrapper functions that return defined values.
+
+```c
+// Supported
+#define ESC 0x1b            /* Defines for numerical and string literals. */
+extern const int pi_const;
+#define PI pi_const         /* Defines aliasing extern variables. */
+
+// Not supported (non-exhaustive list)
+#define COLS  (getenv("COLS") ? atoi(getenv("COLS")) : 80)
+#define MAX(a, b) (a > b ? a : b)
+```
+
+## Reusing generated bindings
+
+There is no way to reuse already generated bindings.  
+Bindgen outputs bindings also for headers that were included in a given header. See @github[#2](#2).
+
+## Type qualifiers
+
+Type qualifiers `const`, `volatile` and `restrict` are not supported.
+
+## Updating extern variables
+
+Extern variables are read-only. See @github[scala-native/scala-native#202](scala-native/scala-native#202).

tests/samples/Function.h

@@ -4,3 +4,21 @@ char one_arg(int a);
 void *two_args(float a, int b);
 double anonymous_args(float, int);
 double variadic_args(double a, char *varArgs, ...);
+
+struct s {
+    int val;
+};
+
+void acceptsStructValue(struct s); // function is skipped with warning
+
+typedef struct s s;
+
+s returnsStructValue(); // function is skipped with warning
+
+union u {
+    int a;
+};
+
+void acceptsUnionValue(union u); // function is skipped with warning
+
+void acceptsArray(int[10]); // it's okay because the type is pointer to int

tests/samples/Function.scala

@@ -6,10 +6,32 @@ import scala.scalanative.native._
 @native.link("bindgentests")
 @native.extern
 object Function {
+  type struct_s = native.CStruct1[native.CInt]
+  type s = struct_s
+  type union_u = native.CArray[Byte, native.Nat._4]
   def no_args(): native.CInt = native.extern
   def void_arg(): native.CFloat = native.extern
   def one_arg(a: native.CInt): native.CChar = native.extern
   def two_args(a: native.CFloat, b: native.CInt): native.Ptr[Byte] = native.extern
   def anonymous_args(anonymous0: native.CFloat, anonymous1: native.CInt): native.CDouble = native.extern
   def variadic_args(a: native.CDouble, varArgs: native.CString, varArgs0: native.CVararg*): native.CDouble = native.extern
+  def acceptsArray(anonymous0: native.Ptr[native.CInt]): Unit = native.extern
 }
+
+import Function._
+
+object FunctionHelpers {
+
+  implicit class struct_s_ops(val p: native.Ptr[struct_s]) extends AnyVal {
+    def `val`: native.CInt = !p._1
+    def `val_=`(value: native.CInt): Unit = !p._1 = value
+  }
+
+  def struct_s()(implicit z: native.Zone): native.Ptr[struct_s] = native.alloc[struct_s]
+
+  implicit class union_u_pos(val p: native.Ptr[union_u]) extends AnyVal {
+    def a: native.Ptr[native.CInt] = p.cast[native.Ptr[native.CInt]]
+    def a_=(value: native.CInt): Unit = !p.cast[native.Ptr[native.CInt]] = value
+  }
+}
+

tests/samples/PrivateMembers.h

@@ -38,7 +38,7 @@ void __privateFunction();
 
 // functions that should not be removed:
 __private_type *getPrivateType();
-void usesPrivateUnion(union __unionWithPrivateName);
+void usesPrivateUnion(union __unionWithPrivateName *);
 void usesPrivateStruct(struct structWithPrivateType *, struct normalStruct *);
 void usesPrivateEnum(enum __privateEnum *);
 

tests/samples/PrivateMembers.scala

@@ -19,7 +19,7 @@ object PrivateMembers {
   type privateStructWithTypedefPtr = native.Ptr[struct_privateStructWithTypedef]
   def getTypeThatUsesPrivateTypes(): pid_t = native.extern
   def getPrivateType(): native.Ptr[__private_type] = native.extern
-  def usesPrivateUnion(anonymous0: union___unionWithPrivateName): Unit = native.extern
+  def usesPrivateUnion(anonymous0: native.Ptr[union___unionWithPrivateName]): Unit = native.extern
   def usesPrivateStruct(anonymous0: native.Ptr[struct_structWithPrivateType], anonymous1: native.Ptr[struct_normalStruct]): Unit = native.extern
   def usesPrivateEnum(anonymous0: native.Ptr[enum___privateEnum]): Unit = native.extern
 }

tests/samples/ReservedWords.h

@@ -20,7 +20,7 @@ union lazy {
 
 typedef union lazy lazy;
 
-type with(match sealed, var implicit, lazy forSome);
+type *with(match sealed, var implicit, lazy *forSome);
 
 typedef match def;
 typedef struct {