Darwin, libgcc : Adjust min version supported for the OS.

Tools from later versions of the OS deprecate or fail to support
earlier OS revisions.

Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>

libgcc/ChangeLog:

	* config.host: Arrange to set min Darwin OS versions from
	the configured host version.
	* config/darwin10-unwind-find-enc-func.c: Do not use current
	headers, but declare the nexessary structures locally to the
	versions in use for Mac OSX 10.6.
	* config/t-darwin: Amend to handle configured min OS
	versions.
	* config/t-darwin-min-1: New.
	* config/t-darwin-min-5: New.
	* config/t-darwin-min-8: New.

6 files changed, 63 insertions, 8 deletions

diff --git a/libgcc/config.host b/libgcc/config.host
index b9975de..9d72120 100644
--- a/libgcc/config.host
+++ b/libgcc/config.host
@@ -233,6 +233,24 @@ case ${host} in
       ;;
   esac
   tmake_file="$tmake_file t-slibgcc-darwin"
+  # newer toolsets produce warnings when building for unsupported versions.
+  case ${host} in
+    *-*-darwin1[89]* | *-*-darwin2* )
+      tmake_file="t-darwin-min-8 $tmake_file"
+      ;;
+    *-*-darwin9* | *-*-darwin1[0-7]*)
+      tmake_file="t-darwin-min-5 $tmake_file"
+      ;;
+    *-*-darwin[4-8]*)
+      tmake_file="t-darwin-min-1 $tmake_file"
+      ;;
+    *)
+      # Fall back to configuring for the oldest system known to work with
+      # all archs and the current sources.
+      tmake_file="t-darwin-min-5 $tmake_file"
+      echo "Warning: libgcc configured to support macOS 10.5" 1>&2
+      ;;
+  esac
   extra_parts="crt3.o libd10-uwfef.a crttms.o crttme.o libemutls_w.a"
   ;;
 *-*-dragonfly*)
diff --git a/libgcc/config/darwin10-unwind-find-enc-func.c b/libgcc/config/darwin10-unwind-find-enc-func.c
index 882ec3a..b08396c 100644
--- a/libgcc/config/darwin10-unwind-find-enc-func.c
+++ b/libgcc/config/darwin10-unwind-find-enc-func.c
@@ -1,8 +1,34 @@
-#include "tconfig.h"
-#include "tsystem.h"
-#include "unwind-dw2-fde.h"
 #include "libgcc_tm.h"
 
+/* This shim is special, it needs to be built for Mac OSX 10.6
+   regardless of the current system version.
+   We must also build it to use the unwinder layout that was
+   present for 10.6 (and not update that).
+   So we copy the referenced structures from unwind-dw2-fde.h
+   to avoid pulling in newer system headers and/or changed
+   layouts.  */
+struct dwarf_eh_bases
+{
+  void *tbase;
+  void *dbase;
+  void *func;
+};
+
+typedef          int  sword __attribute__ ((mode (SI)));
+typedef unsigned int  uword __attribute__ ((mode (SI)));
+
+/* The first few fields of an FDE.  */
+struct dwarf_fde
+{
+  uword length;
+  sword CIE_delta;
+  unsigned char pc_begin[];
+} __attribute__ ((packed, aligned (__alignof__ (void *))));
+
+typedef struct dwarf_fde fde;
+
+extern const fde * _Unwind_Find_FDE (void *, struct dwarf_eh_bases *);
+
 void *
 _darwin10_Unwind_FindEnclosingFunction (void *pc)
 {
@@ -10,5 +36,5 @@ _darwin10_Unwind_FindEnclosingFunction (void *pc)
   const struct dwarf_fde *fde = _Unwind_Find_FDE (pc-1, &bases);
   if (fde)
     return bases.func;
-  return NULL;
+  return (void *) 0;
 }
diff --git a/libgcc/config/t-darwin b/libgcc/config/t-darwin
index 299d26c..a3bb70c 100644
--- a/libgcc/config/t-darwin
+++ b/libgcc/config/t-darwin
@@ -1,15 +1,15 @@
 # Set this as a minimum (unless overriden by arch t-files) since it's a
 # reasonable lowest common denominator that works for all our archs.
-HOST_LIBGCC2_CFLAGS += -mmacosx-version-min=10.4
+HOST_LIBGCC2_CFLAGS += $(DARWIN_MIN_LIB_VERSION)
 
 crt3.o: $(srcdir)/config/darwin-crt3.c
-	$(crt_compile) -mmacosx-version-min=10.4 -c $<
+	$(crt_compile) $(DARWIN_MIN_CRT_VERSION) -c $<
 
 crttms.o: $(srcdir)/config/darwin-crt-tm.c
-	$(crt_compile) -mmacosx-version-min=10.4 -DSTART -c $<
+	$(crt_compile) $(DARWIN_MIN_CRT_VERSION) -DSTART -c $<
 
 crttme.o: $(srcdir)/config/darwin-crt-tm.c
-	$(crt_compile) -mmacosx-version-min=10.4 -DEND -c $<
+	$(crt_compile) $(DARWIN_MIN_CRT_VERSION) -DEND -c $<
 
 # Make emutls weak so that we can deal with -static-libgcc, override the
 # hidden visibility when this is present in libgcc_eh.
@@ -25,6 +25,8 @@ libemutls_w.a: emutls_s.o
 	$(RANLIB_FOR_TARGET) $@
 
 # Patch to __Unwind_Find_Enclosing_Function for Darwin10.
+# This needs to be built for darwin10, regardless of the current platform
+# version.
 d10-uwfef.o: $(srcdir)/config/darwin10-unwind-find-enc-func.c libgcc_tm.h
 	$(crt_compile) -mmacosx-version-min=10.6 -c $<
 
diff --git a/libgcc/config/t-darwin-min-1 b/libgcc/config/t-darwin-min-1
new file mode 100644
index 0000000..8c2cf8a
--- /dev/null
+++ b/libgcc/config/t-darwin-min-1
@@ -0,0 +1,3 @@
+# Support building with -mmacosx-version-min back to 10.1.
+DARWIN_MIN_LIB_VERSION = -mmacosx-version-min=10.4
+DARWIN_MIN_CRT_VERSION = -mmacosx-version-min=10.1
diff --git a/libgcc/config/t-darwin-min-5 b/libgcc/config/t-darwin-min-5
new file mode 100644
index 0000000..1381931
--- /dev/null
+++ b/libgcc/config/t-darwin-min-5
@@ -0,0 +1,3 @@
+# Support building with -mmacosx-version-min back to 10.5.
+DARWIN_MIN_LIB_VERSION = -mmacosx-version-min=10.5
+DARWIN_MIN_CRT_VERSION = -mmacosx-version-min=10.5
diff --git a/libgcc/config/t-darwin-min-8 b/libgcc/config/t-darwin-min-8
new file mode 100644
index 0000000..9efc9dc
--- /dev/null
+++ b/libgcc/config/t-darwin-min-8
@@ -0,0 +1,3 @@
+# Support building with -mmacosx-version-min back to 10.8.
+DARWIN_MIN_LIB_VERSION = -mmacosx-version-min=10.8
+DARWIN_MIN_CRT_VERSION = -mmacosx-version-min=10.8