Fix floating point issues on 32-bit platforms:

https://gitlab.gnome.org/GNOME/json-glib/issues/27

This is an amalgamation of the following upstream commits:
https://gitlab.gnome.org/GNOME/json-glib/commit/70e2648e02232c1a439a7418388f18fee9afb3fe
https://gitlab.gnome.org/GNOME/json-glib/commit/675e27505776a1d77fa1ffd1974284890caec1f4

diff --git a/json-glib/tests/json-test-utils.h b/json-glib/tests/json-test-utils.h
new file mode 100644
index 0000000..83a02c6
--- /dev/null
+++ b/json-glib/tests/json-test-utils.h
@@ -0,0 +1,21 @@
+#include <string.h>
+#include <math.h>
+#include <float.h>
+#include <glib.h>
+#include <json-glib/json-glib.h>
+
+#define json_fuzzy_equals(n1,n2,epsilon) \
+  (((n1) > (n2) ? ((n1) - (n2)) : ((n2) - (n1))) < (epsilon))
+
+#define json_assert_fuzzy_equals(n1,n2,epsilon) \
+  G_STMT_START { \
+    double __n1 = (n1), __n2 = (n2), __epsilon = (epsilon); \
+    if (json_fuzzy_equals (__n1, __n2, __epsilon)) ; else { \
+      g_assertion_message_cmpnum (G_LOG_DOMAIN, __FILE__, __LINE__, G_STRFUNC, \
+                                  #n1 " == " #n2 " (+/- " #epsilon ")", \
+                                  __n1, "==", __n2, 'f'); \
+    } \
+  } G_STMT_END
+
+#define json_assert_almost_equals(n1,n2) \
+  json_assert_fuzzy_equals (n1, n2, DBL_EPSILON)
diff --git a/json-glib/tests/array.c b/json-glib/tests/array.c
index 98afeab..426cd72 100644
--- a/json-glib/tests/array.c
+++ b/json-glib/tests/array.c
@@ -1,9 +1,4 @@
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-
-#include <glib.h>
-#include <json-glib/json-glib.h>
+#include "json-test-utils.h"
 
 static void
 test_empty_array (void)
@@ -37,7 +32,7 @@ test_add_element (void)
 
   json_array_add_double_element (array, 3.14);
   g_assert_cmpint (json_array_get_length (array), ==, 3);
-  g_assert_cmpfloat (json_array_get_double_element (array, 2), ==, 3.14);
+  json_assert_fuzzy_equals (json_array_get_double_element (array, 2), 3.14, 0.001);
 
   json_array_add_boolean_element (array, TRUE);
   g_assert_cmpint (json_array_get_length (array), ==, 4);
diff --git a/json-glib/tests/node.c b/json-glib/tests/node.c
index 23bda63..80beb78 100644
--- a/json-glib/tests/node.c
+++ b/json-glib/tests/node.c
@@ -1,6 +1,4 @@
-#include <glib.h>
-#include <json-glib/json-glib.h>
-#include <string.h>
+#include "json-test-utils.h"
 
 static void
 test_init_int (void)
@@ -19,7 +17,7 @@ test_init_double (void)
   JsonNode *node = json_node_new (JSON_NODE_VALUE);
 
   json_node_set_double (node, 3.14159);
-  g_assert_cmpfloat (json_node_get_double (node), ==, 3.14159);
+  json_assert_fuzzy_equals (json_node_get_double (node), 3.14159, 0.00001);
 
   json_node_free (node);
 }
@@ -119,13 +117,13 @@ test_get_int (void)
 
   json_node_set_int (node, 0);
   g_assert_cmpint (json_node_get_int (node), ==, 0);
-  g_assert_cmpfloat (json_node_get_double (node), ==, 0.0);
+  json_assert_almost_equals (json_node_get_double (node), 0.0);
   g_assert (!json_node_get_boolean (node));
   g_assert (!json_node_is_null (node));
 
   json_node_set_int (node, 42);
   g_assert_cmpint (json_node_get_int (node), ==, 42);
-  g_assert_cmpfloat (json_node_get_double (node), ==, 42.0);
+  json_assert_almost_equals (json_node_get_double (node), 42.0);
   g_assert (json_node_get_boolean (node));
   g_assert (!json_node_is_null (node));
 
@@ -138,7 +136,7 @@ test_get_double (void)
   JsonNode *node = json_node_new (JSON_NODE_VALUE);
 
   json_node_set_double (node, 3.14);
-  g_assert_cmpfloat (json_node_get_double (node), ==, 3.14);
+  json_assert_fuzzy_equals (json_node_get_double (node), 3.14, 0.001);
   g_assert_cmpint (json_node_get_int (node), ==, 3);
   g_assert (json_node_get_boolean (node));
 
@@ -232,9 +230,9 @@ test_gvalue_autopromotion (void)
     g_print ("Expecting a gdouble, got a %s\n", g_type_name (G_VALUE_TYPE (&check))); 
 
   g_assert_cmpint (G_VALUE_TYPE (&check), ==, G_TYPE_DOUBLE);
-  g_assert_cmpfloat ((float) g_value_get_double (&check), ==, 3.14159f);
+  json_assert_fuzzy_equals (g_value_get_double (&check), 3.14159, 0.00001);
   g_assert_cmpint (G_VALUE_TYPE (&value), !=, G_VALUE_TYPE (&check));
-  g_assert_cmpfloat ((gdouble) g_value_get_float (&value), ==, g_value_get_double (&check));
+  json_assert_almost_equals (g_value_get_float (&value), g_value_get_double (&check));
 
   g_value_unset (&value);
   g_value_unset (&check);
diff --git a/json-glib/tests/parser.c b/json-glib/tests/parser.c
index f71584a..8c52a1d 100644
--- a/json-glib/tests/parser.c
+++ b/json-glib/tests/parser.c
@@ -1,11 +1,5 @@
-#include "config.h"
-
+#include "json-test-utils.h"
 #include <stdlib.h>
-#include <stdio.h>
-
-#include <glib.h>
-
-#include <json-glib/json-glib.h>
 
 static const gchar *test_empty_string = "";
 static const gchar *test_empty_array_string = "[ ]";
@@ -38,13 +32,13 @@ verify_string_value (JsonNode *node)
 static void
 verify_double_value (JsonNode *node)
 {
-  g_assert_cmpfloat (10.2e3, ==, json_node_get_double (node));
+  json_assert_fuzzy_equals (10.2e3, json_node_get_double (node), 0.1);
 }
 
 static void
 verify_negative_double_value (JsonNode *node)
 {
-  g_assert_cmpfloat (-3.14, ==, json_node_get_double (node));
+  json_assert_fuzzy_equals (-3.14, json_node_get_double (node), 0.01);
 }
 
 static const struct {
diff --git a/json-glib/tests/reader.c b/json-glib/tests/reader.c
index 43a6aac..9bab312 100644
--- a/json-glib/tests/reader.c
+++ b/json-glib/tests/reader.c
@@ -1,9 +1,4 @@
-#include <stdlib.h>
-#include <stdio.h>
-
-#include <glib.h>
-
-#include <json-glib/json-glib.h>
+#include "json-test-utils.h"
 
 static const gchar *test_base_array_data =
 "[ 0, true, null, \"foo\", 3.14, [ false ], { \"bar\" : 42 } ]";
@@ -78,7 +73,7 @@ test_base_object (void)
   g_assert (json_reader_get_error (reader) == NULL);
 
   json_reader_read_member (reader, "double");
-  g_assert_cmpfloat (json_reader_get_double_value (reader), ==, 42.47);
+  json_assert_fuzzy_equals (json_reader_get_double_value (reader), 42.47, 0.01);
   json_reader_end_element (reader);
 
   g_object_unref (reader);