RISC-V: Improve the error message for the mis-matched ISA versions.

Consider the updated attr-merge-arch-failed-01.d testcase.  Extension
A's version are mis-matched between attr-merge-arch-failed-01a.s and
attr-merge-arch-failed-01b.s.  But the old binutils reports that the
mis-matched extension is M rather than A.  This commit is used to fix
the wrong mis-matched error message.

Besides, when parsing the arch string in the riscv_parse_subset, it
shouldn't be NULL or empty.  However, it might be empty when we failed
to merge the arch string in the riscv_merge_attributes.  Since we should
already issue the correct error message in another side, and the message
- ISA string must begin with rv32 or rv64 - is meaninglesss when the arch
string is empty, so do not issue it.

	bfd/
	* elfnn-riscv.c (riscv_merge_std_ext): Fix to report the correct
	error message when the versions of extension are mis-matched.
	* elfxx-riscv.c (riscv_parse_subset): Don't issue the error when
	the string is empty.

	ld/
	* testsuite/ld-riscv-elf/attr-merge-arch-failed-01.d: Updated.
	* testsuite/ld-riscv-elf/attr-merge-arch-failed-01a.s: Likewise.
	* testsuite/ld-riscv-elf/attr-merge-arch-failed-01b.s: Likewise.

3 files changed, 17 insertions, 4 deletions

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 76055ba..8703aeb 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,10 @@
+2020-09-03  Kito Cheng  <kito.cheng@sifive.com>
+
+	* elfnn-riscv.c (riscv_merge_std_ext): Fix to report the correct
+	error message when the versions of extension are mis-matched.
+	* elfxx-riscv.c (riscv_parse_subset): Don't issue the error when
+	the string is empty.
+
 2020-09-03  Alan Modra  <amodra@gmail.com>
 
 	* xcofflink.c (xcoff_get_archive_info): Allocate xcoff_archive_info
diff --git a/bfd/elfnn-riscv.c b/bfd/elfnn-riscv.c
index 8a3338c..f8de719 100644
--- a/bfd/elfnn-riscv.c
+++ b/bfd/elfnn-riscv.c
@@ -2724,7 +2724,7 @@ riscv_merge_std_ext (bfd *ibfd,
 	  && ((find_in->major_version != find_out->major_version)
 	      || (find_in->minor_version != find_out->minor_version)))
 	{
-	  riscv_version_mismatch (ibfd, in, out);
+	  riscv_version_mismatch (ibfd, find_in, find_out);
 	  return FALSE;
 	}
 
diff --git a/bfd/elfxx-riscv.c b/bfd/elfxx-riscv.c
index 1570f1d..cfdd867 100644
--- a/bfd/elfxx-riscv.c
+++ b/bfd/elfxx-riscv.c
@@ -1519,9 +1519,15 @@ riscv_parse_subset (riscv_parse_subset_t *rps,
     }
   else
     {
-      rps->error_handler
-	(_("-march=%s: ISA string must begin with rv32 or rv64"),
-	 arch);
+      /* Arch string shouldn't be NULL or empty here.  However,
+	 it might be empty only when we failed to merge the arch
+	 string in the riscv_merge_attributes.  We have already
+	 issued the correct error message in another side, so do
+	 not issue this error when the arch string is empty.  */
+      if (strlen (arch))
+	rps->error_handler (
+	  _("-march=%s: ISA string must begin with rv32 or rv64"),
+	  arch);
       return FALSE;
     }