SPDX-FileCopyrightText: 2005 Paul Eggert <eggert@cs.ucla.edu>
SPDX-FileCopyrightText: 2023 Emily Trau <emily@downunderctf.com>

SPDX-License-Identifier: GPL-2.0-or-later

uniq: don't assume fopen cannot return stdin or stdout.
Backport of https://git.savannah.gnu.org/cgit/coreutils.git/commit/?id=786ebb2ceca72f69aa2de701671fb41f53cb1489

--- src/uniq.c
+++ src/uniq.c
@@ -30,6 +30,7 @@
 #include "error.h"
 #include "hard-locale.h"
 #include "posixver.h"
+#include "stdio-safer.h"
 #include "xmemcoll.h"
 #include "xstrtol.h"
 #include "memcasecmp.h"
@@ -267,20 +268,26 @@ check_file (const char *infile, const char *outfile)
   FILE *ostream;
   struct linebuffer lb1, lb2;
   struct linebuffer *thisline, *prevline;
+  bool is_stdin = STREQ (infile, "-");
+  bool is_stdout = STREQ (outfile, "-");
 
-  if (STREQ (infile, "-"))
+  if (is_stdin)
     istream = stdin;
   else
-    istream = fopen (infile, "r");
-  if (istream == NULL)
-    error (EXIT_FAILURE, errno, "%s", infile);
+    {
+      istream = fopen_safer (infile, "r");
+      if (! istream)
+        error (EXIT_FAILURE, errno, "%s", infile);
+    }
 
-  if (STREQ (outfile, "-"))
+  if (is_stdout)
     ostream = stdout;
   else
-    ostream = fopen (outfile, "w");
-  if (ostream == NULL)
-    error (EXIT_FAILURE, errno, "%s", outfile);
+    {
+      ostream = fopen_safer (outfile, "w");
+      if (! ostream)
+        error (EXIT_FAILURE, errno, "%s", outfile);
+    }
 
   thisline = &lb1;
   prevline = &lb2;
@@ -377,12 +384,12 @@ check_file (const char *infile, const char *outfile)
     }
 
  closefiles:
-  if (ferror (istream) || fclose (istream) == EOF)
+  if (!is_stdin && (ferror (istream) || fclose (istream) != 0))
     error (EXIT_FAILURE, errno, _("error reading %s"), infile);
 
   /* Close ostream only if it's not stdout -- the latter is closed
      via the atexit-invoked close_stdout.  */
-  if (ostream != stdout && (ferror (ostream) || fclose (ostream) == EOF))
+  if (!is_stdout && (ferror (ostream) || fclose (ostream) != 0))
     error (EXIT_FAILURE, errno, _("error writing %s"), outfile);
 
   free (lb1.buffer);