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List:       binutils
Subject:    ASSERT in empty output section with address
From:       Alan Modra via Binutils <binutils () sourceware ! org>
Date:       2021-10-28 1:12:55
Message-ID: YXn2R3liQ3qklcUw () squeak ! grove ! modra ! org
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On Thu, Oct 28, 2021 at 08:18:02AM +1030, Alan Modra wrote:
> It is a bug, triggered by the way ld specially treats empty output
> sections.  An empty output section normally doesn't result in the
> linker's current address or dot to change.  So for example a highly
> aligned section won't result in an alignment gap for itself and
> following sections if it is empty.  That resulted in the value of dot
> not being set correctly inside your empty .ram section.

	* ldlang.c (lang_do_assignments_1): Correct "dot" inside ignored
	sections.
	* testsuite/ld-scripts/empty-address-4.d,
	* testsuite/ld-scripts/empty-address-4.s,
	* testsuite/ld-scripts/empty-address-4.t: New test.
	* testsuite/ld-scripts/empty-address.exp: Run it.

diff --git a/ld/ldlang.c b/ld/ldlang.c
index bc3f8b76d35..acd90fa8f42 100644
--- a/ld/ldlang.c
+++ b/ld/ldlang.c
@@ -6481,32 +6481,34 @@ lang_do_assignments_1 (lang_statement_union_type *s,
 	    os = &(s->output_section_statement);
 	    os->after_end = *found_end;
 	    init_opb (os->bfd_section);
-	    if (os->bfd_section != NULL && !os->ignored)
+	    newdot = dot;
+	    if (os->bfd_section != NULL)
 	      {
-		if ((os->bfd_section->flags & SEC_ALLOC) != 0)
+		if (!os->ignored && (os->bfd_section->flags & SEC_ALLOC) != 0)
 		  {
 		    current_section = os;
 		    prefer_next_section = false;
 		  }
-		dot = os->bfd_section->vma;
+		newdot = os->bfd_section->vma;
 	      }
 	    newdot = lang_do_assignments_1 (os->children.head,
-					    os, os->fill, dot, found_end);
+					    os, os->fill, newdot, found_end);
 	    if (!os->ignored)
 	      {
 		if (os->bfd_section != NULL)
 		  {
+		    newdot = os->bfd_section->vma;
+
 		    /* .tbss sections effectively have zero size.  */
 		    if (!IS_TBSS (os->bfd_section)
 			|| bfd_link_relocatable (&link_info))
-		      dot += TO_ADDR (os->bfd_section->size);
+		      newdot += TO_ADDR (os->bfd_section->size);
 
 		    if (os->update_dot_tree != NULL)
 		      exp_fold_tree (os->update_dot_tree,
-				     bfd_abs_section_ptr, &dot);
+				     bfd_abs_section_ptr, &newdot);
 		  }
-		else
-		  dot = newdot;
+		dot = newdot;
 	      }
 	  }
 	  break;
diff --git a/ld/testsuite/ld-scripts/empty-address-4.d b/ld/testsuite/ld-scripts/empty-address-4.d
new file mode 100644
index 00000000000..26b058bc0ae
--- /dev/null
+++ b/ld/testsuite/ld-scripts/empty-address-4.d
@@ -0,0 +1,6 @@
+#ld: -T empty-address-4.t
+#nm: -n
+
+#...
+0+0 [AT] _start
+#pass
diff --git a/ld/testsuite/ld-scripts/empty-address-4.s b/ld/testsuite/ld-scripts/empty-address-4.s
new file mode 100644
index 00000000000..602a02f331f
--- /dev/null
+++ b/ld/testsuite/ld-scripts/empty-address-4.s
@@ -0,0 +1,4 @@
+	.text
+	.global _start
+_start:
+	.dc.a 0, 0
diff --git a/ld/testsuite/ld-scripts/empty-address-4.t b/ld/testsuite/ld-scripts/empty-address-4.t
new file mode 100644
index 00000000000..f25bbfea8ac
--- /dev/null
+++ b/ld/testsuite/ld-scripts/empty-address-4.t
@@ -0,0 +1,11 @@
+SECTIONS
+{
+  .text 0: { *(.text .pr) }
+  .data 0x200:
+  {
+    *(.data)
+    ASSERT (. < 0x400, oops);
+  }
+  .bss : { *(.bss) }
+  /DISCARD/ : { *(.*) }
+}
diff --git a/ld/testsuite/ld-scripts/empty-address.exp b/ld/testsuite/ld-scripts/empty-address.exp
index 1f62372d3d7..060c72d034a 100644
--- a/ld/testsuite/ld-scripts/empty-address.exp
+++ b/ld/testsuite/ld-scripts/empty-address.exp
@@ -32,5 +32,6 @@ run_dump_test empty-address-2b
 run_dump_test empty-address-3a
 run_dump_test empty-address-3b
 run_dump_test empty-address-3c
+run_dump_test empty-address-4
 
 set LDFLAGS $old_LDFLAGS

-- 
Alan Modra
Australia Development Lab, IBM
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