diff --git a/NEWS b/NEWS
index 4f3fc479..c704a45e 100644
--- a/NEWS
+++ b/NEWS
@@ -1,6 +1,11 @@
 In Development:
 # Mentioning Check 0.14.0 for now, to fix distcheck target until next release
 
+* Define CK_ATTRIBUTE_FORMAT for GCC >= 2.95.3, to make use of
+  ‘gnu_printf’ format attribute
+
+* Refactor tests to fix signed - unsigned conversions
+
 
 Sun Jan 26, 2020: Released Check 0.14.0
   based on hash 0076ec62f71d33b5b54530f8471b4c99f50638d7
diff --git a/TODO b/TODO
index 7e53b95b..3045d3f6 100644
--- a/TODO
+++ b/TODO
@@ -59,6 +59,10 @@ Build issues:
 [     ] * Add option BUILD_DOCUMENTATION to CMake (Github #217).
 [     ] * Missing function check in CMake creates def HAVE_FOO=0.
           There should be no HAVE_FOO (Github #195).
+[     ] * CMake and Autotools should check if compiler supports __attribute__ ((format (a, b, c)))
+          to decide if CK_ATTRIBUTE_FORMAT can be defined
+          https://www.gnu.org/software/autoconf-archive/ax_gcc_func_attribute.html
+
 
 Check source code:
 ============
diff --git a/lib/libcompat.h b/lib/libcompat.h
index 816c53bf..ea63a5e8 100644
--- a/lib/libcompat.h
+++ b/lib/libcompat.h
@@ -48,8 +48,10 @@
 
 #if GCC_VERSION_AT_LEAST(2,95,3)
 #define CK_ATTRIBUTE_UNUSED __attribute__ ((unused))
+#define CK_ATTRIBUTE_FORMAT(a, b, c) __attribute__ ((format (a, b, c)))
 #else
 #define CK_ATTRIBUTE_UNUSED
+#define CK_ATTRIBUTE_FORMAT(a, b, c)
 #endif /* GCC 2.95 */
 
 #if GCC_VERSION_AT_LEAST(2,5,0)
diff --git a/src/check.c b/src/check.c
index 2d4ebb68..f74b3849 100644
--- a/src/check.c
+++ b/src/check.c
@@ -54,7 +54,7 @@ int check_micro_version = CHECK_MICRO_VERSION;
 
 const char* current_test_name = NULL;
 
-static int non_pass(int val);
+static int non_pass(enum test_result);
 static Fixture *fixture_create(SFun fun, int ischecked);
 static void tcase_add_fixture(TCase * tc, SFun setup, SFun teardown,
                               int ischecked);
@@ -512,7 +512,7 @@ TestResult **srunner_results(SRunner * sr)
     return trarray;
 }
 
-static int non_pass(int val)
+static int non_pass(enum test_result val)
 {
     return val != CK_PASS;
 }
diff --git a/src/check.h.in b/src/check.h.in
index 2e131d26..fdbc8b05 100644
--- a/src/check.h.in
+++ b/src/check.h.in
@@ -64,8 +64,10 @@ CK_CPPSTART
 
 #if GCC_VERSION_AT_LEAST(2,95,3)
 #define CK_ATTRIBUTE_UNUSED __attribute__ ((unused))
+#define CK_ATTRIBUTE_FORMAT(a, b, c) __attribute__ ((format (a, b, c)))
 #else
 #define CK_ATTRIBUTE_UNUSED
+#define CK_ATTRIBUTE_FORMAT(a, b, c)
 #endif /* GCC 2.95 */
 
 #if GCC_VERSION_AT_LEAST(2,5,0)
@@ -499,10 +501,10 @@ static void __testname ## _fn (int _i CK_ATTRIBUTE_UNUSED)
 #if @HAVE_FORK@
 CK_DLL_EXP void CK_EXPORT _ck_assert_failed(const char *file, int line,
                                             const char *expr,
-                                            ...) CK_ATTRIBUTE_NORETURN;
+                                            ...) CK_ATTRIBUTE_NORETURN CK_ATTRIBUTE_FORMAT(gnu_printf, 3, 4);
 #else
 CK_DLL_EXP void CK_EXPORT _ck_assert_failed(const char *file, int line,
-                                            const char *expr, ...);
+                                            const char *expr, ...) CK_ATTRIBUTE_FORMAT(gnu_printf, 3, 4);
 #endif
 
 /**
diff --git a/src/check_error.h b/src/check_error.h
index c2c8d34e..19580880 100644
--- a/src/check_error.h
+++ b/src/check_error.h
@@ -31,7 +31,7 @@ extern jmp_buf error_jmp_buffer;
 /* Print error message and die
    If fmt ends in colon, include system error information */
 void eprintf(const char *fmt, const char *file, int line,
-             ...) CK_ATTRIBUTE_NORETURN;
+             ...) CK_ATTRIBUTE_NORETURN CK_ATTRIBUTE_FORMAT(gnu_printf, 1, 4);
 /* malloc or die */
 void *emalloc(size_t n);
 void *erealloc(void *, size_t n);
diff --git a/src/check_str.h b/src/check_str.h
index b26eae2b..92697f28 100644
--- a/src/check_str.h
+++ b/src/check_str.h
@@ -21,6 +21,8 @@
 #ifndef CHECK_STR_H
 #define CHECK_STR_H
 
+#include "../lib/libcompat.h"
+
 /* Return a string representation of the given TestResult.  Return
    value has been malloc'd, and must be freed by the caller */
 char *tr_str(TestResult * tr);
@@ -37,6 +39,6 @@ char *tr_short_str(TestResult * tr);
 */
 char *sr_stat_str(SRunner * sr);
 
-char *ck_strdup_printf(const char *fmt, ...);
+char *ck_strdup_printf(const char *fmt, ...) CK_ATTRIBUTE_FORMAT(gnu_printf, 1, 2);
 
 #endif /* CHECK_STR_H */
diff --git a/tests/check_check.h b/tests/check_check.h
index 32e49bc6..d828ee01 100644
--- a/tests/check_check.h
+++ b/tests/check_check.h
@@ -96,6 +96,6 @@ void record_failure_line_num(const int line);
  *
  * If there are no more lines to read, -1 is returned.
  */
-int get_next_failure_line_num(FILE * file);
+long get_next_failure_line_num(FILE * file);
 
 #endif /* CHECK_CHECK_H */
diff --git a/tests/check_check_master.c b/tests/check_check_master.c
index a606708a..aaf45f3f 100644
--- a/tests/check_check_master.c
+++ b/tests/check_check_master.c
@@ -561,7 +561,7 @@ END_TEST
 START_TEST(test_check_failure_lnos)
 {
   int i;
-  int line_no;
+  long line_no;
   int passed = 0;
   int number_failed;
   TestResult *tr;
@@ -652,10 +652,6 @@ END_TEST
 START_TEST(test_check_test_names)
 {
   int i;
-  int line_no;
-  int passed = 0;
-  int number_failed;
-  TestResult *tr;
 
   rewind(test_names_file);
 
@@ -936,9 +932,9 @@ char* get_next_test_name(FILE * file)
 
 void record_failure_line_num(int linenum)
 {
-  int to_write;
-  ssize_t written;
-  int result;
+  size_t to_write;
+  size_t written;
+  int result, chars_printed;
   char string[16];
 
   /*
@@ -947,12 +943,13 @@ void record_failure_line_num(int linenum)
    */
    linenum += 1;
 
-  to_write = snprintf(string, sizeof(string), "%d\n", linenum);
-  if(to_write <= 0)
+  chars_printed = snprintf(string, sizeof(string), "%d\n", linenum);
+  if(chars_printed <= 0 || (size_t) chars_printed >= sizeof(string))
   {
     fprintf(stderr, "%s:%d: Error in call to snprintf:", __FILE__, __LINE__);
     exit(1);
   }
+  to_write = (size_t) chars_printed;
 
   if(line_num_failures == NULL)
   {
@@ -969,7 +966,7 @@ void record_failure_line_num(int linenum)
   written = fwrite(string, 1, to_write, line_num_failures);
   if(written != to_write)
   {
-    fprintf(stderr, "%s:%d: Error in call to fwrite, wrote %zd instead of %d:", __FILE__, __LINE__, written, to_write);
+    fprintf(stderr, "%s:%d: Error in call to fwrite, wrote %zd instead of %zu:", __FILE__, __LINE__, written, to_write);
     exit(1);
   }
 
@@ -981,13 +978,13 @@ void record_failure_line_num(int linenum)
   }
 }
 
-int get_next_failure_line_num(FILE * file)
+long get_next_failure_line_num(FILE * file)
 {
   char * line = NULL;
   char * end = NULL;
   size_t length;
   ssize_t written;
-  int value = -1;
+  long value = -1;
 
   written = getline(&line, &length, file);
 
diff --git a/tests/check_check_sub.c b/tests/check_check_sub.c
index ddfea1d2..184a3bf7 100644
--- a/tests/check_check_sub.c
+++ b/tests/check_check_sub.c
@@ -1092,7 +1092,7 @@ END_TEST
 
 START_TEST(test_ck_assert_double_eq_with_promotion)
 {
-  float x = 0.1;
+  float x = 0.1F;
   double y = x;
 
   record_test_name(tcase_name());
@@ -1103,7 +1103,7 @@ END_TEST
 
 START_TEST(test_ck_assert_double_eq_with_conv)
 {
-  float x = 0.1;
+  float x = 0.1F;
 
   record_test_name(tcase_name());
 
@@ -1608,7 +1608,7 @@ END_TEST
 
 START_TEST(test_ck_assert_ldouble_eq_with_promotion)
 {
-  float x = 1.1;
+  float x = 1.1F;
   long double y = x;
 
   record_test_name(tcase_name());
@@ -1619,7 +1619,7 @@ END_TEST
 
 START_TEST(test_ck_assert_ldouble_eq_with_conv)
 {
-  float x = 1.1;
+  float x = 1.1F;
   long double y = x;
 
   record_test_name(tcase_name());
diff --git a/tests/check_check_tags.c b/tests/check_check_tags.c
index e4f485ab..7c77e302 100644
--- a/tests/check_check_tags.c
+++ b/tests/check_check_tags.c
@@ -658,7 +658,7 @@ START_TEST(include_w_spaces)
 
 Suite *make_tag_suite(void)
 {
-    TCase *set_get_tags, *no_filters;
+    TCase *no_filters;
     TCase *include_filters, *exclude_filters;
 #if HAVE_DECL_SETENV
     TCase *include_filters_env, *exclude_filters_env;
diff --git a/tests/check_set_max_msg_size.c b/tests/check_set_max_msg_size.c
index 92a3bab5..d7c91bd6 100644
--- a/tests/check_set_max_msg_size.c
+++ b/tests/check_set_max_msg_size.c
@@ -52,7 +52,6 @@ static Suite *make_set_max_msg_size_suite(void)
 
 int main (int argc, char *argv[])
 {
-    int n;
     SRunner *sr;
 
     if (argc != 2) {
@@ -64,8 +63,8 @@ int main (int argc, char *argv[])
      * Run the test suite. This is intended to trigger the "Message is too long" error.
      * Actual success/failure is determined by examining the output.
      */
-    check_set_max_msg_size(32);            /* 1st call has no effect since   */
-    check_set_max_msg_size(atoi(argv[1])); /* the 2nd call will override it. */
+    check_set_max_msg_size(32);                         /* 1st call has no effect since   */
+    check_set_max_msg_size(strtoul(argv[1], NULL, 10)); /* the 2nd call will override it. */
     sr = srunner_create(make_set_max_msg_size_suite());
     srunner_run_all(sr, CK_NORMAL);
     srunner_free(sr);