diff --git a/support/Makefile b/support/Makefile
index 1bda81e55e..fb9f4291d7 100644
--- a/support/Makefile
+++ b/support/Makefile
@@ -52,9 +52,11 @@ libsupport-routines = \
   support_format_hostent \
   support_format_netent \
   support_isolate_in_subprocess \
+  support_quote_blob \
   support_record_failure \
   support_run_diff \
   support_shared_allocate \
+  support_test_compare_blob \
   support_test_compare_failure \
   support_write_file_string \
   support_test_main \
@@ -150,8 +152,10 @@ tests = \
   tst-support-namespace \
   tst-support_capture_subprocess \
   tst-support_format_dns_packet \
+  tst-support_quote_blob \
   tst-support_record_failure \
   tst-test_compare \
+  tst-test_compare_blob \
   tst-xreadlink \
 
 ifeq ($(run-built-tests),yes)
diff --git a/support/check.h b/support/check.h
index 2192f38941..f16fb3fead 100644
--- a/support/check.h
+++ b/support/check.h
@@ -64,6 +64,8 @@ __BEGIN_DECLS
         (1, __FILE__, __LINE__, #expr);                         \
   })
 
+
+
 int support_print_failure_impl (const char *file, int line,
                                 const char *format, ...)
   __attribute__ ((nonnull (1), format (printf, 3, 4)));
@@ -141,6 +143,24 @@ void support_test_compare_failure (const char *file, int line,
                                    int right_size);
 
 
+/* Compare [LEFT, LEFT + LEFT_LENGTH) with [RIGHT, RIGHT +
+   RIGHT_LENGTH) and report a test failure if the arrays are
+   different.  LEFT_LENGTH and RIGHT_LENGTH are measured in bytes.  If
+   the length is null, the corresponding pointer is ignored (i.e., it
+   can be NULL).  The blobs should be reasonably short because on
+   mismatch, both are printed.  */
+#define TEST_COMPARE_BLOB(left, left_length, right, right_length)       \
+  (support_test_compare_blob (left, left_length, right, right_length,   \
+                              __FILE__, __LINE__,                       \
+                              #left, #left_length, #right, #right_length))
+
+void support_test_compare_blob (const void *left, unsigned long left_length,
+                                const void *right, unsigned long right_length,
+                                const char *file, int line,
+                                const char *left_exp, const char *left_len_exp,
+                                const char *right_exp,
+                                const char *right_len_exp);
+
 /* Internal function called by the test driver.  */
 int support_report_failure (int status)
   __attribute__ ((weak, warn_unused_result));
diff --git a/support/support.h b/support/support.h
index bc5827ed87..b61fe0735c 100644
--- a/support/support.h
+++ b/support/support.h
@@ -59,6 +59,12 @@ void support_shared_free (void *);
    process on error.  */
 void support_write_file_string (const char *path, const char *contents);
 
+/* Quote the contents of the byte array starting at BLOB, of LENGTH
+   bytes, in such a way that the result string can be included in a C
+   literal (in single/double quotes, without putting the quotes into
+   the result).  */
+char *support_quote_blob (const void *blob, size_t length);
+
 /* Error-checking wrapper functions which terminate the process on
    error.  */
 
diff --git a/support/support_quote_blob.c b/support/support_quote_blob.c
new file mode 100644
index 0000000000..0b97f318de
--- /dev/null
+++ b/support/support_quote_blob.c
@@ -0,0 +1,80 @@
+/* Quote a blob so that it can be used in C literals.
+   Copyright (C) 2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/support.h>
+#include <support/xmemstream.h>
+
+char *
+support_quote_blob (const void *blob, size_t length)
+{
+  struct xmemstream out;
+  xopen_memstream (&out);
+
+  const unsigned char *p = blob;
+  for (size_t i = 0; i < length; ++i)
+    {
+      unsigned char ch = p[i];
+      switch (ch)
+        {
+          case '\a':
+            putc_unlocked ('\\', out.out);
+            putc_unlocked ('a', out.out);
+            break;
+          case '\b':
+            putc_unlocked ('\\', out.out);
+            putc_unlocked ('b', out.out);
+            break;
+          case '\f':
+            putc_unlocked ('\\', out.out);
+            putc_unlocked ('f', out.out);
+            break;
+          case '\n':
+            putc_unlocked ('\\', out.out);
+            putc_unlocked ('n', out.out);
+            break;
+          case '\r':
+            putc_unlocked ('\\', out.out);
+            putc_unlocked ('r', out.out);
+            break;
+          case '\t':
+            putc_unlocked ('\\', out.out);
+            putc_unlocked ('t', out.out);
+            break;
+          case '\v':
+            putc_unlocked ('\\', out.out);
+            putc_unlocked ('v', out.out);
+            break;
+          case '\\':
+          case '\'':
+          case '\"':
+            putc_unlocked ('\\', out.out);
+            putc_unlocked (ch, out.out);
+            break;
+        default:
+          if (ch < ' ' || ch > '~')
+            /* Use octal sequences because they are fixed width,
+               unlike hexadecimal sequences.  */
+            fprintf (out.out, "\\%03o", ch);
+          else
+            putc_unlocked (ch, out.out);
+        }
+    }
+
+  xfclose_memstream (&out);
+  return out.buffer;
+}
diff --git a/support/support_test_compare_blob.c b/support/support_test_compare_blob.c
new file mode 100644
index 0000000000..8b738636ff
--- /dev/null
+++ b/support/support_test_compare_blob.c
@@ -0,0 +1,76 @@
+/* Check two binary blobs for equality.
+   Copyright (C) 2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <support/check.h>
+#include <support/support.h>
+#include <support/xmemstream.h>
+
+static void
+report_length (const char *what, unsigned long length, const char *expr)
+{
+  printf ("  %s %lu bytes (from %s)\n", what, length, expr);
+}
+
+static void
+report_blob (const char *what, const unsigned char *blob, unsigned long length,
+             const char *expr)
+{
+  if (length > 0)
+    {
+      printf ("  %s (evaluated from %s):\n", what, expr);
+      char *quoted = support_quote_blob (blob, length);
+      printf ("      \"%s\"\n", quoted);
+      free (quoted);
+
+      fputs ("     ", stdout);
+      for (unsigned long i = 0; i < length; ++i)
+        printf (" %02X", blob[i]);
+      putc ('\n', stdout);
+    }
+}
+
+void
+support_test_compare_blob (const void *left, unsigned long left_length,
+                           const void *right, unsigned long right_length,
+                           const char *file, int line,
+                           const char *left_expr, const char *left_len_expr,
+                           const char *right_expr, const char *right_len_expr)
+{
+  /* No differences are possible if both lengths are null.  */
+  if (left_length == 0 && right_length == 0)
+    return;
+
+  if (left_length != right_length || left == NULL || right == NULL
+      || memcmp (left, right, left_length) != 0)
+    {
+      support_record_failure ();
+      printf ("%s:%d: error: blob comparison failed\n", file, line);
+      if (left_length == right_length)
+        printf ("  blob length: %lu bytes\n", left_length);
+      else
+        {
+          report_length ("left length: ", left_length, left_len_expr);
+          report_length ("right length:", right_length, right_len_expr);
+        }
+      report_blob ("left", left, left_length, left_expr);
+      report_blob ("right", right, right_length, right_expr);
+    }
+}
diff --git a/support/tst-support_quote_blob.c b/support/tst-support_quote_blob.c
new file mode 100644
index 0000000000..2e2ab2ad03
--- /dev/null
+++ b/support/tst-support_quote_blob.c
@@ -0,0 +1,43 @@
+/* Test the support_quote_blob function.
+   Copyright (C) 2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/check.h>
+#include <support/support.h>
+#include <string.h>
+#include <stdlib.h>
+
+static int
+do_test (void)
+{
+  char *p = support_quote_blob ("", 0);
+  TEST_COMPARE (strlen (p), 0);
+  free (p);
+
+  p = support_quote_blob ("[]\'\"X", 4);
+  TEST_COMPARE (strcmp (p, "[]\\'\\\""), 0);
+  free (p);
+
+  p = support_quote_blob ("\r\n\t\a\b\f\v\1\177\200\377\0@", 14);
+  TEST_COMPARE (strcmp (p, "\\r\\n\\t\\a\\b\\f\\v\\001"
+                        "\\177\\200\\377\\000@\\000"), 0);
+  free (p);
+
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/support/tst-test_compare_blob.c b/support/tst-test_compare_blob.c
new file mode 100644
index 0000000000..51f1f88e82
--- /dev/null
+++ b/support/tst-test_compare_blob.c
@@ -0,0 +1,118 @@
+/* Basic test for the TEST_COMPARE_BLOB macro.
+   Copyright (C) 2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <string.h>
+#include <support/check.h>
+#include <support/capture_subprocess.h>
+
+static void
+subprocess (void *closure)
+{
+  /* These tests should fail.  */
+  TEST_COMPARE_BLOB ("", 0, "", 1);    /* Line 28.  */
+  TEST_COMPARE_BLOB ("X", 1, "", 1);   /* Line 29.  */
+  TEST_COMPARE_BLOB ("abcd", 3, "abcd", 4); /* Line 30.  */
+  TEST_COMPARE_BLOB ("abcd", 4, "abcD", 4); /* Line 31.  */
+  TEST_COMPARE_BLOB ("abcd", 4, NULL, 0); /* Line 32.  */
+  TEST_COMPARE_BLOB (NULL, 0, "abcd", 4); /* Line 33.  */
+}
+
+/* Same contents, different addresses.  */
+char buffer_abc_1[] = "abc";
+char buffer_abc_2[] = "abc";
+
+static int
+do_test (void)
+{
+  /* This should succeed.  */
+  TEST_COMPARE_BLOB ("", 0, "", 0);
+  TEST_COMPARE_BLOB ("", 0, buffer_abc_1, 0);
+  TEST_COMPARE_BLOB (buffer_abc_1, 0, "", 0);
+  TEST_COMPARE_BLOB (NULL, 0, "", 0);
+  TEST_COMPARE_BLOB ("", 0, NULL, 0);
+  TEST_COMPARE_BLOB (NULL, 0, NULL, 0);
+  TEST_COMPARE_BLOB ("", 1, "", 1);
+
+  for (size_t i = 0; i <= sizeof (buffer_abc_1); ++i)
+    TEST_COMPARE_BLOB (buffer_abc_1, i, buffer_abc_2, i);
+
+  struct support_capture_subprocess proc = support_capture_subprocess
+    (&subprocess, NULL);
+
+  /* Discard the reported error.  */
+  support_record_failure_reset ();
+
+  puts ("info: *** subprocess output starts ***");
+  fputs (proc.out.buffer, stdout);
+  puts ("info: *** subprocess output ends ***");
+
+  TEST_VERIFY
+    (strcmp (proc.out.buffer,
+"tst-test_compare_blob.c:27: error: blob comparison failed\n"
+"  left length:  0 bytes (from 0)\n"
+"  right length: 1 bytes (from 1)\n"
+"  right (evaluated from \"\"):\n"
+"      \"\\000\"\n"
+"      00\n"
+"tst-test_compare_blob.c:28: error: blob comparison failed\n"
+"  blob length: 1 bytes\n"
+"  left (evaluated from \"X\"):\n"
+"      \"X\"\n"
+"      58\n"
+"  right (evaluated from \"\"):\n"
+"      \"\\000\"\n"
+"      00\n"
+"tst-test_compare_blob.c:29: error: blob comparison failed\n"
+"  left length:  3 bytes (from 3)\n"
+"  right length: 4 bytes (from 4)\n"
+"  left (evaluated from \"abcd\"):\n"
+"      \"abc\"\n"
+"      61 62 63\n"
+"  right (evaluated from \"abcd\"):\n"
+"      \"abcd\"\n"
+"      61 62 63 64\n"
+"tst-test_compare_blob.c:30: error: blob comparison failed\n"
+"  blob length: 4 bytes\n"
+"  left (evaluated from \"abcd\"):\n"
+"      \"abcd\"\n"
+"      61 62 63 64\n"
+"  right (evaluated from \"abcD\"):\n"
+"      \"abcD\"\n"
+"      61 62 63 44\n"
+"tst-test_compare_blob.c:31: error: blob comparison failed\n"
+"  left length:  4 bytes (from 4)\n"
+"  right length: 0 bytes (from 0)\n"
+"  left (evaluated from \"abcd\"):\n"
+"      \"abcd\"\n"
+"      61 62 63 64\n"
+"tst-test_compare_blob.c:32: error: blob comparison failed\n"
+"  left length:  0 bytes (from 0)\n"
+"  right length: 4 bytes (from 4)\n"
+"  right (evaluated from \"abcd\"):\n"
+"      \"abcd\"\n"
+"      61 62 63 64\n"
+             ) == 0);
+
+  /* Check that there is no output on standard error.  */
+  support_capture_subprocess_check (&proc, "TEST_COMPARE_BLOB",
+                                    0, sc_allow_stdout);
+
+  return 0;
+}
+
+#include <support/test-driver.c>
