[binutils-gdb/binutils-2_31-branch] Improve the code in the assembler to detect and reject a duplicate input and output file.

[Nick Clifton]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=bdfdf1717407e4857fe671f902434273a71b4fe1

commit bdfdf1717407e4857fe671f902434273a71b4fe1
Author: Robert Yang <liezhi.yang@windriver.com>
Date:   Mon Sep 17 16:26:58 2018 +0100

    Improve the code in the assembler to detect and reject a duplicate input and output file.
    
    	* as.c (main): Improve check for input file matching output file.

Diff:
---
 gas/ChangeLog |  7 +++++++
 gas/as.c      | 27 ++++++++++++++++++++-------
 2 files changed, 27 insertions(+), 7 deletions(-)

diff --git a/gas/ChangeLog b/gas/ChangeLog
index fe0d12a..31ee451 100644
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,3 +1,10 @@
+2018-09-17  Nick Clifton  <nickc@redhat.com>
+
+	backport from mainline:
+	* 2018-08-14  Robert Yang  <liezhi.yang@windriver.com>
+
+	* as.c (main): Improve check for input file matching output file.
+
 2018-08-10  H.J. Lu  <hongjiu.lu@intel.com>
 
 	* testsuite/gas/i386/evex-no-scale.s: Removed.
diff --git a/gas/as.c b/gas/as.c
index 02c7d29..919c24a 100644
--- a/gas/as.c
+++ b/gas/as.c
@@ -1254,14 +1254,27 @@ main (int argc, char ** argv)
 	{
 	  struct stat sib;
 
-	  if (stat (argv[i], &sib) == 0)
+	  /* Check that the input file and output file are different.  */
+	  if (stat (argv[i], &sib) == 0
+	      && sib.st_ino == sob.st_ino
+	      /* POSIX emulating systems may support stat() but if the
+		 underlying file system does not support a file serial number
+		 of some kind then they will return 0 for the inode.  So
+		 two files with an inode of 0 may not actually be the same.
+		 On real POSIX systems no ordinary file will ever have an
+		 inode of 0.  */
+	      && sib.st_ino != 0
+	      /* Different files may have the same inode number if they
+		 reside on different devices, so check the st_dev field as
+		 well.  */
+	      && sib.st_dev == sob.st_dev)
 	    {
-	      if (sib.st_ino == sob.st_ino && sib.st_ino != 0)
-		{
-		  /* Don't let as_fatal remove the output file!  */
-		  out_file_name = NULL;
-		  as_fatal (_("The input and output files must be distinct"));
-		}
+	      const char *saved_out_file_name = out_file_name;
+
+	      /* Don't let as_fatal remove the output file!  */
+	      out_file_name = NULL;
+	      as_fatal (_("The input '%s' and output '%s' files are the same"),
+			argv[i], saved_out_file_name);
 	    }
 	}
     }