[binutils-gdb] Fix buffer underrun bug in the TI C30 disassembler.

[gdb-buildbot@sergiodj.net]

*** TEST RESULTS FOR COMMIT f44b758d3133ef0a7f3131c1e12ed20feb33ee61 ***

commit f44b758d3133ef0a7f3131c1e12ed20feb33ee61
Author:     Nick Clifton <nickc@redhat.com>
AuthorDate: Tue Sep 3 15:37:12 2019 +0100
Commit:     Nick Clifton <nickc@redhat.com>
CommitDate: Tue Sep 3 15:37:12 2019 +0100

    Fix buffer underrun bug in the TI C30 disassembler.
    
            PR 24961
            * tic30-dis.c (get_indirect_operand): Check for bufcnt being
            greater than zero before indexing via (bufcnt -1).

diff --git a/opcodes/ChangeLog b/opcodes/ChangeLog
index 87e3f74663..64b6a07ac4 100644
--- a/opcodes/ChangeLog
+++ b/opcodes/ChangeLog
@@ -1,3 +1,9 @@
+2019-09-03  Nick Clifton  <nickc@redhat.com>
+
+	PR 24961
+	* tic30-dis.c (get_indirect_operand): Check for bufcnt being
+	greater than zero before indexing via (bufcnt -1).
+
 2019-09-03  Nick Clifton  <nickc@redhat.com>
 
 	PR 24958
diff --git a/opcodes/tic30-dis.c b/opcodes/tic30-dis.c
index c64aceb29f..668c519df8 100644
--- a/opcodes/tic30-dis.c
+++ b/opcodes/tic30-dis.c
@@ -253,7 +253,9 @@ get_indirect_operand (unsigned short fragment,
 		for (i = 0, bufcnt = 0; i < len; i++, bufcnt++)
 		  {
 		    buffer[bufcnt] = current_ind->syntax[i];
-		    if (buffer[bufcnt - 1] == 'a' && buffer[bufcnt] == 'r')
+		    if (bufcnt > 0
+			&& buffer[bufcnt - 1] == 'a'
+			&& buffer[bufcnt] == 'r')
 		      buffer[++bufcnt] = arnum + '0';
 		    if (buffer[bufcnt] == '('
 			&& current_ind->displacement == DISP_REQUIRED)