[pushed] Darwin : Mark the mod init/term section starts with a linker-visible sym.

diff --git a/gcc/config/darwin.c b/gcc/config/darwin.c
index 5d1d13c80aa..667fda79a60 100644
--- a/gcc/config/darwin.c
+++ b/gcc/config/darwin.c
@@ -109,6 +109,9 @@  static bool ld_uses_coal_sects = false;
    each FDE.  */
 static bool ld_needs_eh_markers = false;
 
+/* Emit a section-start symbol for mod init and term sections.  */
+static bool ld_init_term_start_labels = false;
+
 /* Section names.  */
 section * darwin_sections[NUM_DARWIN_SECTIONS];
 
@@ -1838,6 +1841,11 @@  finalize_ctors ()
   else
     switch_to_section (darwin_sections[constructor_section]);
 
+  /* Where needed, provide a linker-visible section-start symbol so that we
+     have stable output between debug and non-debug.  */
+  if (ld_init_term_start_labels)
+    fputs (MACHOPIC_INDIRECT ? "_Mod.init:\n" : "_CTOR.sect:\n", asm_out_file);
+
   if (vec_safe_length (ctors) > 1)
     ctors->qsort (sort_cdtor_records);
   FOR_EACH_VEC_SAFE_ELT (ctors, i, elt)
@@ -1858,6 +1866,11 @@  finalize_dtors ()
   else
     switch_to_section (darwin_sections[destructor_section]);
 
+  /* Where needed, provide a linker-visible section-start symbol so that we
+     have stable output between debug and non-debug.  */
+  if (ld_init_term_start_labels)
+    fputs (MACHOPIC_INDIRECT ? "_Mod.term:\n" : "_DTOR.sect:\n", asm_out_file);
+
   if (vec_safe_length (dtors) > 1)
     dtors->qsort (sort_cdtor_records);
   FOR_EACH_VEC_SAFE_ELT (dtors, i, elt)
@@ -3228,11 +3241,25 @@  darwin_override_options (void)
       /* Earlier versions are not specifically accounted, until required.  */
     }
 
-  /* Older Darwin ld could not coalesce weak entities without them being
-     placed in special sections.  */
-  if (darwin_target_linker
-      && (strverscmp (darwin_target_linker, MIN_LD64_NO_COAL_SECTS) < 0))
-    ld_uses_coal_sects = true;
+  /* Some codegen needs to account for the capabilities of the target
+     linker.  */
+  if (darwin_target_linker)
+    {
+      /* Older Darwin ld could not coalesce weak entities without them being
+	 placed in special sections.  */
+      if (strverscmp (darwin_target_linker, MIN_LD64_NO_COAL_SECTS) < 0)
+	ld_uses_coal_sects = true;
+
+      /* Some newer assemblers emit section start temp symbols for mod init
+	 and term sections if there is no suitable symbol present already.
+	 The temp symbols are linker visible and therefore appear in the
+	 symbol tables.  Since the temp symbol number can vary when debug is
+	 enabled, that causes compare-debug fails.  The solution is to provide
+	 a stable linker-visible symbol.  */
+      if (strverscmp (darwin_target_linker,
+		      MIN_LD64_INIT_TERM_START_LABELS) >= 0)
+	ld_init_term_start_labels = true;
+    }
 
   /* In principle, this should be c-family only.  However, we really need to
      set sensible defaults for LTO as well, since the section selection stuff
diff --git a/gcc/config/darwin.h b/gcc/config/darwin.h
index b1be561e854..f1d92f87e9a 100644
--- a/gcc/config/darwin.h
+++ b/gcc/config/darwin.h
@@ -1104,6 +1104,9 @@  extern void darwin_driver_init (unsigned int *,struct cl_decoded_option **);
    needed, and there is no need for the compiler to emit them.  */
 #define MIN_LD64_OMIT_STUBS "62.1"
 
+/* Emit start labels for init and term sections from this version.  */
+#define MIN_LD64_INIT_TERM_START_LABELS "136.0"
+
 /* If we have no definition for the linker version, pick the minimum version
    that will bootstrap the compiler.  */
 #ifndef LD64_VERSION