diff --git a/tests/test-marray.c b/tests/test-marray.c
index b54012e6..c331b168 100644
--- a/tests/test-marray.c
+++ b/tests/test-marray.c
@@ -207,12 +207,12 @@ static void test_mpz(void)
   testobj_init (z);
 
   // Test empty
-  FILE *f = fopen ("a-marray.dat", "wt");
+  FILE *f = m_core_fopen ("a-marray.dat", "wt");
   if (!f) abort();
   array_mpz_out_str(f, array1);
   fclose (f);
 
-  f = fopen ("a-marray.dat", "rt");
+  f = m_core_fopen ("a-marray.dat", "rt");
   if (!f) abort();
   bool b = array_mpz_in_str (array2, f);
   assert (b == true);
@@ -225,12 +225,12 @@ static void test_mpz(void)
     array_mpz_push_back (array1, z);
   }
   
-  f = fopen ("a-marray.dat", "wt");
+  f = m_core_fopen ("a-marray.dat", "wt");
   if (!f) abort();
   array_mpz_out_str(f, array1);
   fclose (f);
 
-  f = fopen ("a-marray.dat", "rt");
+  f = m_core_fopen ("a-marray.dat", "rt");
   if (!f) abort();
   b = array_mpz_in_str (array2, f);
   assert (b == true);
diff --git a/tests/test-mbitset.c b/tests/test-mbitset.c
index f62194ee..01504948 100644
--- a/tests/test-mbitset.c
+++ b/tests/test-mbitset.c
@@ -231,12 +231,12 @@ static void test_str(void)
   for(int i = 0; i < 200; i++)
     bitset_push_back(set1, ((size_t) i*17547854547UL >> 4)&1) ;
   
-  FILE *f = fopen ("a-mbitset.dat", "wt");
+  FILE *f = m_core_fopen ("a-mbitset.dat", "wt");
   if (!f) abort();
   bitset_out_str(f, set1);
   fclose (f);
 
-  f = fopen ("a-mbitset.dat", "rt");
+  f = m_core_fopen ("a-mbitset.dat", "rt");
   if (!f) abort();
   bool b = bitset_in_str (set2, f);
   assert (b == true);
diff --git a/tests/test-mbptree.c b/tests/test-mbptree.c
index 57c83f33..0ffc31de 100644
--- a/tests/test-mbptree.c
+++ b/tests/test-mbptree.c
@@ -405,12 +405,12 @@ static void test_io(void)
     assert(*endp == 0);
     assert (btree_my_equal_p (tree1, tree2));
 
-    FILE *f = fopen ("a-mbptree.dat", "wt");
+    FILE *f = m_core_fopen ("a-mbptree.dat", "wt");
     if (!f) abort();
     btree_my_out_str(f, tree1);
     fclose (f);
 
-    f = fopen ("a-mbptree.dat", "rt");
+    f = m_core_fopen ("a-mbptree.dat", "rt");
     if (!f) abort();
     b = btree_my_in_str (tree2, f);
     assert (b == true);
@@ -431,12 +431,12 @@ static void test_io(void)
     assert(*endp == 0);
     assert (btree_my_equal_p (tree1, tree2));
 
-    f = fopen ("a-mbptree.dat", "wt");
+    f = m_core_fopen ("a-mbptree.dat", "wt");
     if (!f) abort();
     btree_my_out_str(f, tree1);
     fclose (f);
 
-    f = fopen ("a-mbptree.dat", "rt");
+    f = m_core_fopen ("a-mbptree.dat", "rt");
     if (!f) abort();
     b = btree_my_in_str (tree2, f);
     assert (b == true);
@@ -458,12 +458,12 @@ static void test_io_set(void)
     assert(*endp == 0);
     assert (btree_myset_equal_p (tree1, tree2));
 
-    FILE *f = fopen ("a-mbptree.dat", "wt");
+    FILE *f = m_core_fopen ("a-mbptree.dat", "wt");
     if (!f) abort();
     btree_myset_out_str(f, tree1);
     fclose (f);
 
-    f = fopen ("a-mbptree.dat", "rt");
+    f = m_core_fopen ("a-mbptree.dat", "rt");
     if (!f) abort();
     b = btree_myset_in_str (tree2, f);
     assert (b == true);
@@ -485,12 +485,12 @@ static void test_io_set(void)
     assert(*endp == 0);
     assert (btree_myset_equal_p (tree1, tree2));
 
-    f = fopen ("a-mbptree.dat", "wt");
+    f = m_core_fopen ("a-mbptree.dat", "wt");
     if (!f) abort();
     btree_myset_out_str(f, tree1);
     fclose (f);
 
-    f = fopen ("a-mbptree.dat", "rt");
+    f = m_core_fopen ("a-mbptree.dat", "rt");
     if (!f) abort();
     b = btree_myset_in_str (tree2, f);
     assert (b == true);
diff --git a/tests/test-mdeque.c b/tests/test-mdeque.c
index eb9c3303..5251fc8c 100644
--- a/tests/test-mdeque.c
+++ b/tests/test-mdeque.c
@@ -276,12 +276,12 @@ static void test_io(void)
   M_LET(z, TESTOBJ_OPLIST)
   M_LET(str, STRING_OPLIST) {
     // Test empty
-    FILE *f = fopen ("a-marray.dat", "wt");
+    FILE *f = m_core_fopen ("a-marray.dat", "wt");
     if (!f) abort();
     deque_mpz_out_str(f, d1);
     fclose (f);
 
-    f = fopen ("a-marray.dat", "rt");
+    f = m_core_fopen ("a-marray.dat", "rt");
     if (!f) abort();
     bool b = deque_mpz_in_str (d2, f);
     assert (b == true);
@@ -294,12 +294,12 @@ static void test_io(void)
       deque_mpz_push_back (d1, z);
     }
   
-    f = fopen ("a-marray.dat", "wt");
+    f = m_core_fopen ("a-marray.dat", "wt");
     if (!f) abort();
     deque_mpz_out_str(f, d1);
     fclose (f);
     
-    f = fopen ("a-marray.dat", "rt");
+    f = m_core_fopen ("a-marray.dat", "rt");
     if (!f) abort();
     b = deque_mpz_in_str (d2, f);
     assert (b == true);
diff --git a/tests/test-mdict.c b/tests/test-mdict.c
index f9f5bfbf..ff321ff6 100644
--- a/tests/test-mdict.c
+++ b/tests/test-mdict.c
@@ -119,11 +119,11 @@ static void check_io(void)
     assert (*sp == 0);
     assert (dict_str_equal_p(dict, dict2));
 
-    FILE *f = fopen ("a-mdict.dat", "wt");
+    FILE *f = m_core_fopen ("a-mdict.dat", "wt");
     if (!f) abort();
     dict_str_out_str(f, dict);
     fclose (f);
-    f = fopen ("a-mdict.dat", "rt");
+    f = m_core_fopen ("a-mdict.dat", "rt");
     if (!f) abort();
     b = dict_str_in_str(dict2, f);
     assert (b == true);
@@ -270,7 +270,7 @@ static void test1(void)
   string_init(key);
   string_init(ref);
 
-  FILE *f = fopen("dict.txt", "rt");
+  FILE *f = m_core_fopen("dict.txt", "rt");
   if (!f) abort();
   dict_str_set_at(dict, STRING_CTE("LICENCE"), STRING_CTE("BSD3"));
   assert(string_equal_p(*dict_str_cget(dict, STRING_CTE("LICENCE")), STRING_CTE("BSD3")));
@@ -286,7 +286,7 @@ static void test1(void)
   fclose(f);
   assert(dict_str_size(dict) == 19);
   
-  f = fopen("dict.txt", "rt");
+  f = m_core_fopen("dict.txt", "rt");
   if (!f) abort();
   while (!feof(f) && !ferror(f)) {
     string_fgets(key, f, STRING_READ_PURE_LINE);
diff --git a/tests/test-mlist.c b/tests/test-mlist.c
index fb78cb47..c7918937 100644
--- a/tests/test-mlist.c
+++ b/tests/test-mlist.c
@@ -251,14 +251,14 @@ static void test_mpz(void)
   }
   assert (testobj_get_ui(s) == 1000*999/2);
 
-  FILE *f = fopen ("a-mlist.dat", "wt");
+  FILE *f = m_core_fopen ("a-mlist.dat", "wt");
   if (!f) abort();
   list_mpz_out_str(f, v);
   fclose (f);
 
   list_mpz_t list2;
   list_mpz_init(list2);
-  f = fopen ("a-mlist.dat", "rt");
+  f = m_core_fopen ("a-mlist.dat", "rt");
   bool b = list_mpz_in_str (list2, f);
   assert (b == true);
   fclose(f);
@@ -603,13 +603,13 @@ static void test_out_default_oplist(void)
 {
   M_LET(str, string_t)
     M_LET(list, l2, list_int_t) {
-    FILE *f = fopen ("a-mlist.dat", "wt");
+    FILE *f = m_core_fopen ("a-mlist.dat", "wt");
     if (!f) abort();
     list_int_push_back(list, 2);
     list_int_push_back(list, 3);
     list_int_out_str(f, list);
     fclose(f);
-    f = fopen("a-mlist.dat", "rt");
+    f = m_core_fopen("a-mlist.dat", "rt");
     if (!f) abort();
     char buffer[1024];
     assert (fgets(buffer, 1024, f) == buffer);
@@ -617,7 +617,7 @@ static void test_out_default_oplist(void)
     fclose(f);
     list_int_get_str(str, list, false);
     assert (string_equal_str_p(str, "[3,2]"));
-    f = fopen("a-mlist.dat", "rt");
+    f = m_core_fopen("a-mlist.dat", "rt");
     if (!f) abort();
     assert (list_int_in_str(l2, f) == true);
     assert (list_int_equal_p(l2, list));
diff --git a/tests/test-mrbtree.c b/tests/test-mrbtree.c
index 3ef28d4a..3b78b3af 100644
--- a/tests/test-mrbtree.c
+++ b/tests/test-mrbtree.c
@@ -195,7 +195,7 @@ static void test_uint_permut(void)
 static void test_float(void)
 {
   M_LET(tree, FLOAT_OP) {
-    for(float f = -17.42; f < 17.42; f+=0.01)
+    for(float f = -17.42f; f < 17.42f; f+=0.01f)
       rbtree_float_push (tree, f);
     bool p = false;
     float g;
@@ -214,12 +214,12 @@ static void test_io(void)
   M_LET(str, STRING_OPLIST)
   M_LET(tree1, tree2, UINT_OPLIST) {
     // Empty one
-    FILE *f = fopen ("a-mrbtree.dat", "wt");
+    FILE *f = m_core_fopen ("a-mrbtree.dat", "wt");
     if (!f) abort();
     rbtree_uint_out_str(f, tree1);
     fclose (f);
 
-    f = fopen ("a-mrbtree.dat", "rt");
+    f = m_core_fopen ("a-mrbtree.dat", "rt");
     if (!f) abort();
     bool b = rbtree_uint_in_str (tree2, f);
     assert (b == true);
@@ -238,12 +238,12 @@ static void test_io(void)
     for(unsigned int i = 0 ; i < 10; i++)
       rbtree_uint_push(tree1, i);
 
-    f = fopen ("a-mrbtree.dat", "wt");
+    f = m_core_fopen ("a-mrbtree.dat", "wt");
     if (!f) abort();
     rbtree_uint_out_str(f, tree1);
     fclose (f);
 
-    f = fopen ("a-mrbtree.dat", "rt");
+    f = m_core_fopen ("a-mrbtree.dat", "rt");
     if (!f) abort();
     b = rbtree_uint_in_str (tree2, f);
     assert (b == true);
diff --git a/tests/test-mserial-bin.c b/tests/test-mserial-bin.c
index 9bbb424b..94f064de 100644
--- a/tests/test-mserial-bin.c
+++ b/tests/test-mserial-bin.c
@@ -67,7 +67,7 @@ static void test_out_empty(void)
   my2_init(el1);
   my2_init(el2);
   
-  FILE *f = fopen ("a-mbin.dat", "wt");
+  FILE *f = m_core_fopen ("a-mbin.dat", "wt");
   if (!f) abort();
   M_LET( (serial, f), m_serial_bin_write_t) {
     ret = my2_out_serial(serial, el1);
@@ -75,7 +75,7 @@ static void test_out_empty(void)
   }
   fclose(f);
 
-  f = fopen ("a-mbin.dat", "rt");
+  f = m_core_fopen ("a-mbin.dat", "rt");
   if (!f) abort();
   M_LET( (serial, f), m_serial_bin_read_t) {
     ret = my2_in_serial(el2, serial);
@@ -116,7 +116,7 @@ static void test_out_fill(void)
   d2_set_at(el2->data->valh, STRING_CTE("Paul"), 1);
   d2_set_at(el2->data->valh, STRING_CTE("Smith"), 2);
   
-  f = fopen ("a-mbin.dat", "wt");
+  f = m_core_fopen ("a-mbin.dat", "wt");
   if (!f) abort();
   m_serial_bin_write_init(out, f);
   ret = my2_out_serial(out, el2);
@@ -124,7 +124,7 @@ static void test_out_fill(void)
   m_serial_bin_write_clear(out);
   fclose(f);
 
-  f = fopen ("a-mbin.dat", "rt");
+  f = m_core_fopen ("a-mbin.dat", "rt");
   if (!f) abort();
   m_serial_bin_read_init(in, f);
   ret = my2_in_serial(el1, in);
diff --git a/tests/test-mserial-json.c b/tests/test-mserial-json.c
index db913c2d..9c3fbadf 100644
--- a/tests/test-mserial-json.c
+++ b/tests/test-mserial-json.c
@@ -69,7 +69,7 @@ static void test_out_empty(void)
   my2_init(el1);
   my2_init(el2);
   
-  FILE *f = fopen ("a-mjson.dat", "wt");
+  FILE *f = m_core_m_core_fopen ("a-mjson.dat", "wt");
   if (!f) abort();
   m_serial_json_write_init(out, f);
   ret = my2_out_serial(out, el1);
@@ -77,7 +77,7 @@ static void test_out_empty(void)
   m_serial_json_write_clear(out);
   fclose(f);
 
-  f = fopen ("a-mjson.dat", "rt");
+  f = m_core_m_core_fopen ("a-mjson.dat", "rt");
   if (!f) abort();
   static const char expected[] = "{ \"activated\":false,\"data\":{ \"vala\":0,\"valb\":0.000000,\"valc\":false,\"vald\":\"\",\"vale\":[],\"valf\":{},\"valg\":[],\"valh\":{}}";
   char get[sizeof expected];
@@ -85,7 +85,7 @@ static void test_out_empty(void)
   assert (strcmp(get, expected) == 0);
   fclose(f);
   
-  f = fopen ("a-mjson.dat", "rt");
+  f = m_core_m_core_fopen ("a-mjson.dat", "rt");
   if (!f) abort();
   m_serial_json_read_init(in, f);
   ret = my2_in_serial(el2, in);
@@ -108,7 +108,7 @@ static void test_out_fill(void)
   my2_init(el1);
   my2_init(el2);
   
-  FILE *f = fopen("a-mjson.dat", "wt");
+  FILE *f = m_core_m_core_fopen("a-mjson.dat", "wt");
   if (!f) abort();
   fprintf(f,
           "{\n"
@@ -124,7 +124,7 @@ static void test_out_fill(void)
           "    \"valc\": true   } }\n");
   fclose(f);
 
-  f = fopen ("a-mjson.dat", "rt");
+  f = m_core_m_core_fopen ("a-mjson.dat", "rt");
   if (!f) abort();
   m_serial_json_read_init(in, f);
   ret = my2_in_serial(el2, in);
@@ -132,7 +132,7 @@ static void test_out_fill(void)
   m_serial_json_read_clear(in);
   fclose(f);
   
-  f = fopen ("a-mjson.dat", "wt");
+  f = m_core_m_core_fopen ("a-mjson.dat", "wt");
   if (!f) abort();
   m_serial_json_write_init(out, f);
   ret = my2_out_serial(out, el2);
@@ -140,7 +140,7 @@ static void test_out_fill(void)
   m_serial_json_write_clear(out);
   fclose(f);
 
-  f = fopen ("a-mjson.dat", "rt");
+  f = m_core_m_core_fopen ("a-mjson.dat", "rt");
   if (!f) abort();
   static const char expected[] = "{ \"activated\":false,\"data\":{ \"vala\":1742,\"valb\":-2.300000,\"valc\":true,\"vald\":\"This is a test\",\"vale\":[1,2,3],\"valf\":{\"is_bool\":true},\"valg\":[1,2,3,4,5,6],\"valh\":{\"steeve\":-4,\"jane\":3}}}";
   static const char expected2[] = "{ \"activated\":false,\"data\":{ \"vala\":1742,\"valb\":-2.300000,\"valc\":true,\"vald\":\"This is a test\",\"vale\":[1,2,3],\"valf\":{\"is_bool\":true},\"valg\":[1,2,3,4,5,6],\"valh\":{\"jane\":3,\"steeve\":-4}}}";
@@ -149,7 +149,7 @@ static void test_out_fill(void)
   assert (strcmp(get, expected) == 0 || strcmp(get, expected2) == 0);
   fclose(f);
   
-  f = fopen ("a-mjson.dat", "rt");
+  f = m_core_m_core_fopen ("a-mjson.dat", "rt");
   if (!f) abort();
   m_serial_json_read_init(in, f);
   ret = my2_in_serial(el1, in);
diff --git a/tests/test-mtuple.c b/tests/test-mtuple.c
index 8d4830fc..54c481e3 100644
--- a/tests/test-mtuple.c
+++ b/tests/test-mtuple.c
@@ -132,12 +132,12 @@ static void check_io(void)
     assert (pair_str_equal_p(pair, pair2) == true);
     assert(*end == 0);
 
-    FILE *f = fopen("a-mtuple.dat", "wt");
+    FILE *f = m_core_fopen("a-mtuple.dat", "wt");
     if (!f) abort();
     pair_str_out_str(f, pair);
     fclose(f);
     
-    f = fopen("a-mtuple.dat", "rt");
+    f = m_core_fopen("a-mtuple.dat", "rt");
     if (!f) abort();
     b = pair_str_in_str(pair2, f);
     assert (b);
diff --git a/tests/test-mvariant.c b/tests/test-mvariant.c
index 3f4973fc..5e83fc3b 100644
--- a/tests/test-mvariant.c
+++ b/tests/test-mvariant.c
@@ -219,12 +219,12 @@ test_io(void)
   M_LET(s, STRING_OPLIST)
   M_LET(x, y, VARIANT_OPLIST(single, STRING_OPLIST)) {
     // Check empty
-    FILE *f = fopen ("a-mvariant.dat", "wt");
+    FILE *f = m_core_fopen ("a-mvariant.dat", "wt");
     if (!f) abort();
     single_out_str(f, x);
     fclose (f);
 
-    f = fopen ("a-mvariant.dat", "rt");
+    f = m_core_fopen ("a-mvariant.dat", "rt");
     bool b = single_in_str (y, f);
     assert (b == true);
     fclose(f);
@@ -241,12 +241,12 @@ test_io(void)
     // Fill in the variant
     single_set_s (x, s);
 
-    f = fopen ("a-mvariant.dat", "wt");
+    f = m_core_fopen ("a-mvariant.dat", "wt");
     if (!f) abort();
     single_out_str(f, x);
     fclose (f);
 
-    f = fopen ("a-mvariant.dat", "rt");
+    f = m_core_fopen ("a-mvariant.dat", "rt");
     b = single_in_str (y, f);
     assert (b == true);
     fclose(f);
diff --git a/tests/test-obj.h b/tests/test-obj.h
index 0a2e2b3a..51477a2e 100644
--- a/tests/test-obj.h
+++ b/tests/test-obj.h
@@ -103,7 +103,7 @@ static void testobj_out_str(FILE *f, const testobj_t z)
 static bool testobj_in_str(testobj_t z, FILE *f)
 {
   z->n = 1;
-  return fscanf(f, "%u", &z->ptr[0]) == 1;
+  return m_core_fscanf(f, "%u", &z->ptr[0]) == 1;
 }
 
 static bool testobj_parse_str(testobj_t z, const char str[], const char **endptr)