Darwin, objective-c - register gnu-runtime headers correctly.

Darwin is able to use two runtimes for objective-c; the
default is its native "NeXT" runtime, but also it can build
code using the "gnu-runtime".  In order to do this, we have to
be able to find the gnu-runtime headers (which are installed
into the compiler's tree).

The process to do this is erroneously prepending the sysroot
to this when a sysroot is in force.  The gnu-runtime headers have
never been installed in a Darwin (macOS) SDK so we must make
sure that they are found local to the compiler.

gcc/

2019-05-18  Iain Sandoe  <iain@sandoe.co.uk>

	* config/darwin-c.c (darwin_register_objc_includes): Do not
	prepend the sysroot when building gnu-runtime header search
	paths.

From-SVN: r271371

gcc/ChangeLog

 2019-05-18  Iain Sandoe  <iain@sandoe.co.uk>
 
+	* config/darwin-c.c (darwin_register_objc_includes): Do not
+	prepend the sysroot when building gnu-runtime header search
+	paths.
+
+2019-05-18  Iain Sandoe  <iain@sandoe.co.uk>
+
 	* config/darwin.c (darwin_file_end): Use switch_to_section ()
 	instead of direct output of the asm.
 

gcc/config/darwin-c.c

@@ -463,41 +463,32 @@ static const char *framework_defaults [] =
 /* Register the GNU objective-C runtime include path if STDINC.  */
 
 void
-darwin_register_objc_includes (const char *sysroot, const char *iprefix,
-			       int stdinc)
+darwin_register_objc_includes (const char *sysroot ATTRIBUTE_UNUSED,
+			       const char *iprefix, int stdinc)
 {
-  const char *fname;
-  size_t len;
-  /* We do not do anything if we do not want the standard includes. */
-  if (!stdinc)
-    return;
-
-  fname = GCC_INCLUDE_DIR "-gnu-runtime";
-
-  /* Register the GNU OBJC runtime include path if we are compiling  OBJC
-    with GNU-runtime.  */
+  /* If we want standard includes;  Register the GNU OBJC runtime include
+     path if we are compiling OBJC with GNU-runtime.
+     This path is compiler-relative, we don't want to prepend the sysroot
+     since it's not expected to find the headers there.  */
 
-  if (c_dialect_objc () && !flag_next_runtime)
+  if (stdinc && c_dialect_objc () && !flag_next_runtime)
     {
+      const char *fname = GCC_INCLUDE_DIR "-gnu-runtime";
       char *str;
-      /* See if our directory starts with the standard prefix.
+      size_t len;
+
+     /* See if our directory starts with the standard prefix.
 	 "Translate" them, i.e. replace /usr/local/lib/gcc... with
 	 IPREFIX and search them first.  */
-      if (iprefix && (len = cpp_GCC_INCLUDE_DIR_len) != 0 && !sysroot
+      if (iprefix && (len = cpp_GCC_INCLUDE_DIR_len) != 0
 	  && !strncmp (fname, cpp_GCC_INCLUDE_DIR, len))
 	{
 	  str = concat (iprefix, fname + len, NULL);
-          /* FIXME: wrap the headers for C++awareness.  */
-	  add_path (str, INC_SYSTEM, /*c++aware=*/false, false);
+	  add_path (str, INC_SYSTEM, /*c++aware=*/true, false);
 	}
 
-      /* Should this directory start with the sysroot?  */
-      if (sysroot)
-	str = concat (sysroot, fname, NULL);
-      else
-	str = update_path (fname, "");
-
-      add_path (str, INC_SYSTEM, /*c++aware=*/false, false);
+      str = update_path (fname, "");
+      add_path (str, INC_SYSTEM, /*c++aware=*/true, false);
     }
 }