Also disallow global alias of common symbol

We can't create alias of common symbol.  Local alias of common symbol has
been disallowed.  But global alias of common symbol is disallowed when the
common symbol is seen first and silently dropped otherwise.  This patch
disallows alias of common symbol in all cases.

gas/

	PR gas/21667
	* read.c (pseudo_set): Update error message for alias of common
	symbol.
	* write.c (write_object_file): Disallow both local and global
	aliases of common symbol.
	* testsuite/gas/elf/common5a.d: New file.
	* testsuite/gas/elf/common5a.l: Likewise.
	* testsuite/gas/elf/common5a.s: Likewise.
	* testsuite/gas/elf/common5b.d: Likewise.
	* testsuite/gas/elf/common5b.l: Likewise.
	* testsuite/gas/elf/common5b.s: Likewise.
	* testsuite/gas/elf/common5c.d: Likewise.
	* testsuite/gas/elf/common5c.s: Likewise.
	* testsuite/gas/elf/common5d.d: Likewise.
	* testsuite/gas/elf/common5d.s: Likewise.
	* testsuite/gas/elf/elf.exp: Run common5a, common5b, common5c
	and common5d.

14 files changed, 61 insertions, 4 deletions

diff --git a/gas/ChangeLog b/gas/ChangeLog
index adeb38b..dd61142 100644
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,3 +1,23 @@
+2017-08-11  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR gas/21667
+	* read.c (pseudo_set): Update error message for alias of common
+	symbol.
+	* write.c (write_object_file): Disallow both local and global
+	aliases of common symbol.
+	* testsuite/gas/elf/common5a.d: New file.
+	* testsuite/gas/elf/common5a.l: Likewise.
+	* testsuite/gas/elf/common5a.s: Likewise.
+	* testsuite/gas/elf/common5b.d: Likewise.
+	* testsuite/gas/elf/common5b.l: Likewise.
+	* testsuite/gas/elf/common5b.s: Likewise.
+	* testsuite/gas/elf/common5c.d: Likewise.
+	* testsuite/gas/elf/common5c.s: Likewise.
+	* testsuite/gas/elf/common5d.d: Likewise.
+	* testsuite/gas/elf/common5d.s: Likewise.
+	* testsuite/gas/elf/elf.exp: Run common5a, common5b, common5c
+	and common5d.
+
 2017-08-10  Nick Clifton  <nickc@redhat.com>
 
 	PR gas/21939
diff --git a/gas/read.c b/gas/read.c
index 9627ef5..0b0b058 100644
--- a/gas/read.c
+++ b/gas/read.c
@@ -3870,7 +3870,7 @@ pseudo_set (symbolS *symbolP)
 	  symbolS *s = exp.X_add_symbol;
 
 	  if (S_IS_COMMON (s))
-	    as_bad (_("`%s' can't be equated to common symbol '%s'"),
+	    as_bad (_("`%s' can't be equated to common symbol `%s'"),
 		    S_GET_NAME (symbolP), S_GET_NAME (s));
 
 	  S_SET_SEGMENT (symbolP, seg);
diff --git a/gas/testsuite/gas/elf/common5a.d b/gas/testsuite/gas/elf/common5a.d
new file mode 100644
index 0000000..9c790e6
--- /dev/null
+++ b/gas/testsuite/gas/elf/common5a.d
@@ -0,0 +1,5 @@
+#source: common5a.s
+#as: 
+#error-output: common5a.l
+#not-target: alpha-*-*
+# The Alpha target uses its own .set pseudo-insn.
diff --git a/gas/testsuite/gas/elf/common5a.l b/gas/testsuite/gas/elf/common5a.l
new file mode 100644
index 0000000..7574dc6
--- /dev/null
+++ b/gas/testsuite/gas/elf/common5a.l
@@ -0,0 +1,2 @@
+[^:]*: Assembler messages:
+[^:]*: Error: `foo1' can't be equated to common symbol `foo'
diff --git a/gas/testsuite/gas/elf/common5a.s b/gas/testsuite/gas/elf/common5a.s
new file mode 100644
index 0000000..d4b0acf
--- /dev/null
+++ b/gas/testsuite/gas/elf/common5a.s
@@ -0,0 +1,3 @@
+	.set	foo1,foo
+	.globl	foo1
+	.comm	foo,8,8
diff --git a/gas/testsuite/gas/elf/common5b.d b/gas/testsuite/gas/elf/common5b.d
new file mode 100644
index 0000000..b1dabdc
--- /dev/null
+++ b/gas/testsuite/gas/elf/common5b.d
@@ -0,0 +1,5 @@
+#source: common5b.s
+#as: 
+#error-output: common5b.l
+#not-target: alpha-*-*
+# The Alpha target uses its own .set pseudo-insn.
diff --git a/gas/testsuite/gas/elf/common5b.l b/gas/testsuite/gas/elf/common5b.l
new file mode 100644
index 0000000..171bed0
--- /dev/null
+++ b/gas/testsuite/gas/elf/common5b.l
@@ -0,0 +1,2 @@
+[^:]*: Assembler messages:
+[^:]*:2: Error: `foo1' can't be equated to common symbol `foo'
diff --git a/gas/testsuite/gas/elf/common5b.s b/gas/testsuite/gas/elf/common5b.s
new file mode 100644
index 0000000..df79fcb
--- /dev/null
+++ b/gas/testsuite/gas/elf/common5b.s
@@ -0,0 +1,3 @@
+	.comm	foo,8,8
+	.set	foo1,foo
+	.globl	foo1
diff --git a/gas/testsuite/gas/elf/common5c.d b/gas/testsuite/gas/elf/common5c.d
new file mode 100644
index 0000000..1e106ad
--- /dev/null
+++ b/gas/testsuite/gas/elf/common5c.d
@@ -0,0 +1,5 @@
+#source: common5c.s
+#as: 
+#error-output: common5a.l
+#not-target: alpha-*-*
+# The Alpha target uses its own .set pseudo-insn.
diff --git a/gas/testsuite/gas/elf/common5c.s b/gas/testsuite/gas/elf/common5c.s
new file mode 100644
index 0000000..fa9db8d
--- /dev/null
+++ b/gas/testsuite/gas/elf/common5c.s
@@ -0,0 +1,2 @@
+	.set	foo1,foo
+	.comm	foo,8,8
diff --git a/gas/testsuite/gas/elf/common5d.d b/gas/testsuite/gas/elf/common5d.d
new file mode 100644
index 0000000..9f51636
--- /dev/null
+++ b/gas/testsuite/gas/elf/common5d.d
@@ -0,0 +1,5 @@
+#source: common5d.s
+#as: 
+#error-output: common5b.l
+#not-target: alpha-*-*
+# The Alpha target uses its own .set pseudo-insn.
diff --git a/gas/testsuite/gas/elf/common5d.s b/gas/testsuite/gas/elf/common5d.s
new file mode 100644
index 0000000..6da5cb3
--- /dev/null
+++ b/gas/testsuite/gas/elf/common5d.s
@@ -0,0 +1,2 @@
+	.comm	foo,8,8
+	.set	foo1,foo
diff --git a/gas/testsuite/gas/elf/elf.exp b/gas/testsuite/gas/elf/elf.exp
index 1284619..6737486 100644
--- a/gas/testsuite/gas/elf/elf.exp
+++ b/gas/testsuite/gas/elf/elf.exp
@@ -252,6 +252,10 @@ if { [is_elf_format] } then {
 	run_dump_test "common3b"
 	run_dump_test "common4a"
 	run_dump_test "common4b"
+	run_dump_test "common5a"
+	run_dump_test "common5b"
+	run_dump_test "common5c"
+	run_dump_test "common5d"
     }
 
     run_dump_test "strtab"
diff --git a/gas/write.c b/gas/write.c
index 8efdbc5..4f6547d 100644
--- a/gas/write.c
+++ b/gas/write.c
@@ -2107,12 +2107,11 @@ write_object_file (void)
 
 	      if (S_IS_COMMON (symp)
 		  && !TC_FAKE_LABEL (sname)
-		  && !S_IS_WEAKREFR (symp)
-		  && (!S_IS_EXTERNAL (symp) || S_IS_LOCAL (symp)))
+		  && !S_IS_WEAKREFR (symp))
 		{
 		  expressionS *e = symbol_get_value_expression (symp);
 
-		  as_bad (_("Local symbol `%s' can't be equated to common symbol `%s'"),
+		  as_bad (_("`%s' can't be equated to common symbol `%s'"),
 			  sname, S_GET_NAME (e->X_add_symbol));
 		}
 	      if (S_GET_SEGMENT (symp) == reg_section)