Merge remote-tracking branch 'origin/swift-4.0-branch' into stable
diff --git a/docs/Modules.rst b/docs/Modules.rst
index 141d3b8..2b1bde2 100644
--- a/docs/Modules.rst
+++ b/docs/Modules.rst
@@ -360,6 +360,7 @@
Name.framework/
Modules/module.modulemap Module map for the framework
Headers/ Subdirectory containing framework headers
+ PrivateHeaders/ Subdirectory containing framework private headers
Frameworks/ Subdirectory containing embedded frameworks
Resources/ Subdirectory containing additional resources
Name Symbolic link to the shared library for the framework
@@ -842,6 +843,16 @@
easier to split a library's public and private APIs along header
boundaries.
+When writing a private module as part of a *framework*, it's recommended that:
+
+* Headers for this module are present in the ``PrivateHeaders``
+ framework subdirectory.
+* The private module is defined as a *submodule* of the public framework (if
+ there's one), similar to how ``Foo.Private`` is defined in the example above.
+* The ``explicit`` keyword should be used to guarantee that its content will
+ only be available when the submodule itself is explicitly named (through a
+ ``@import`` for example).
+
Modularizing a Platform
=======================
To get any benefit out of modules, one needs to introduce module maps for software libraries starting at the bottom of the stack. This typically means introducing a module map covering the operating system's headers and the C standard library headers (in ``/usr/include``, for a Unix system).
diff --git a/lib/Headers/tgmath.h b/lib/Headers/tgmath.h
index 318e118..34e26dc 100644
--- a/lib/Headers/tgmath.h
+++ b/lib/Headers/tgmath.h
@@ -22,12 +22,21 @@
*
\*===----------------------------------------------------------------------===*/
-#ifndef __TGMATH_H
-#define __TGMATH_H
+#ifndef __CLANG_TGMATH_H
+#define __CLANG_TGMATH_H
/* C99 7.22 Type-generic math <tgmath.h>. */
#include <math.h>
+/*
+ * Allow additional definitions and implementation-defined values on Apple
+ * platforms. This is done after #include <math.h> to avoid depcycle conflicts
+ * between libcxx and darwin in C++ modules builds.
+ */
+#if defined(__APPLE__) && __STDC_HOSTED__ && __has_include_next(<tgmath.h>)
+# include_next <tgmath.h>
+#else
+
/* C++ handles type genericity with overloading in math.h. */
#ifndef __cplusplus
#include <complex.h>
@@ -1371,4 +1380,5 @@
#undef _TG_ATTRS
#endif /* __cplusplus */
-#endif /* __TGMATH_H */
+#endif /* __has_include_next */
+#endif /* __CLANG_TGMATH_H */
diff --git a/test/Headers/Inputs/usr/include/math.h b/test/Headers/Inputs/usr/include/math.h
new file mode 100644
index 0000000..4171d4f
--- /dev/null
+++ b/test/Headers/Inputs/usr/include/math.h
@@ -0,0 +1 @@
+// math.h
diff --git a/test/Headers/Inputs/usr/include/tgmath.h b/test/Headers/Inputs/usr/include/tgmath.h
new file mode 100644
index 0000000..897962d
--- /dev/null
+++ b/test/Headers/Inputs/usr/include/tgmath.h
@@ -0,0 +1,4 @@
+#ifndef SYS_TGMATH_H
+#define SYS_TGMATH_H
+
+#endif /* SYS_TGMATH_H */
diff --git a/test/Headers/tgmath-darwin.c b/test/Headers/tgmath-darwin.c
new file mode 100644
index 0000000..916605a
--- /dev/null
+++ b/test/Headers/tgmath-darwin.c
@@ -0,0 +1,12 @@
+// REQUIRES: system-darwin
+// RUN: %clang -target x86_64-apple-darwin10 -fsyntax-only -std=c11 -isysroot %S/Inputs %s
+#include <tgmath.h>
+
+// Test the #include_next of tgmath.h works on Darwin.
+#ifndef SYS_TGMATH_H
+ #error "SYS_TGMATH_H not defined"
+#endif
+
+#ifndef __CLANG_TGMATH_H
+ #error "__CLANG_TGMATH_H not defined"
+#endif
