stdlib: tweak import declarations

Ensure that the functions which are declared with @_silgen_name for importing
from external libraries are described with the correct linkage.  If the declared
functions are marked with internal or no linkage, the declaration for the import
will be given internal linkage.  However, this is incorrect if the definition is
not part of the image.

The remaining uses were filtered on the assumption that the swift standard
library is statically linked and provides the definitions for those symbols and
thus will be part of the image.

This was noticed by manual inspection of the IR generated.  Thanks to Dmitri
Gribenko for the hint about the trampoline construction.

Author: compnerd

stdlib/public/SDK/Darwin/Misc.mm

@@ -13,6 +13,9 @@
 #include <fcntl.h>
 #include <semaphore.h>
 
+#define _REENTRANT
+#include <math.h>
+
 extern "C" int 
 _swift_Darwin_open(const char *path, int oflag, mode_t mode) {
   return open(path, oflag, mode);
@@ -42,3 +45,17 @@
   return fcntl(fd, cmd, ptr);
 }
 
+extern "C" float
+_swift_Darwin_lgammaf_r(float x, int *psigngam) {
+  return lgammaf_r(x, psigngam);
+}
+
+extern "C" double
+_swift_Darwin_lgamma_r(double x, int *psigngam) {
+  return lgamma_r(x, psigngam);
+}
+
+extern "C" long double
+_swift_Darwin_lgammal_r(long double x, int *psigngam) {
+  return lgammal_r(x, psigngam);
+}

stdlib/public/SDK/Darwin/tgmath.swift.gyb

@@ -259,9 +259,10 @@ public func scalbn(x: ${T}, _ n: Int) -> ${T} {
 % for T, CT, f in AllFloatTypes():
 % # The real lgamma_r is not imported because it hides behind macro _REENTRANT.
 @warn_unused_result
-@_silgen_name("lgamma${f}_r") 
+@_silgen_name("_swift_Darwin_lgamma${f}_r")
 func _swift_Darwin_lgamma${f}_r(_: ${CT},
                                 _: UnsafeMutablePointer<CInt>) -> ${CT}
+
 @_transparent
 @warn_unused_result
 public func lgamma(x: ${T}) -> (${T}, Int) {

stdlib/public/SDK/ObjectiveC/CMakeLists.txt

@@ -1,4 +1,5 @@
 add_swift_library(swiftObjectiveC IS_SDK_OVERLAY
+  ObjectiveC.mm
   ObjectiveC.swift
   SWIFT_MODULE_DEPENDS Darwin)
 

stdlib/public/SDK/ObjectiveC/ObjectiveC.mm

@@ -0,0 +1,28 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2016 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See http://swift.org/LICENSE.txt for license information
+// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+#include <objc/objc-api.h>
+
+OBJC_EXPORT
+void *objc_autoreleasePoolPush(void);
+
+OBJC_EXPORT
+void objc_autoreleasePoolPop(void *);
+
+extern "C" void *_swift_objc_autoreleasePoolPush(void) {
+  return objc_autoreleasePoolPush();
+}
+
+extern "C" void _swift_objc_autoreleasePoolPop(void *context) {
+  return objc_autoreleasePoolPop(context);
+}
+

stdlib/public/SDK/ObjectiveC/ObjectiveC.swift

@@ -196,10 +196,10 @@ typealias Zone = NSZone
 //===----------------------------------------------------------------------===//
 
 @warn_unused_result
-@_silgen_name("objc_autoreleasePoolPush")
+@_silgen_name("_swift_objc_autoreleasePoolPush")
 func __pushAutoreleasePool() -> OpaquePointer
 
-@_silgen_name("objc_autoreleasePoolPop")
+@_silgen_name("_swift_objc_autoreleasePoolPop")
 func __popAutoreleasePool(pool: OpaquePointer)
 
 public func autoreleasepool(@noescape code: () -> Void) {