y2038 addon: Fix that check can never return True, add tests (#2417)

* y2038 addon: Fix that check can never return True, add tests

At the beginning of `check_y2038_safe()` the variable `y2038safe` should
be initialized with `True` and only be set to `False` if there are any
issues. Otherwise it could never become `True`.
In the unit tests the return value of `check_y2038_safe()` is now
verified. But it does not yet work for the "good" example. The "good"
example also returns `False` since it finds warnings in the include
file. So this verification is marked with a "FIXME" comment.

* y2038 tests: Add "good" test file that does not use time functionality

The test file y2038-test-5-good-no-time-used.c does not use any time
functionality so the y2038 addon is not allowed to issue any warnings
and the check must return with `True` (code is safe).

addons/test/test-y2038.py

@@ -18,7 +18,8 @@ from .util import dump_create, dump_remove, convert_json_output
 TEST_SOURCE_FILES = ['./addons/test/y2038/y2038-test-1-bad-time-bits.c',
                      './addons/test/y2038/y2038-test-2-no-time-bits.c',
                      './addons/test/y2038/y2038-test-3-no-use-time-bits.c',
-                     './addons/test/y2038/y2038-test-4-good.c']
+                     './addons/test/y2038/y2038-test-4-good.c',
+                     './addons/test/y2038/y2038-test-5-good-no-time-used.c']
 
 
 def setup_module(module):
@@ -34,7 +35,8 @@ def teardown_module(module):
 
 
 def test_1_bad_time_bits(capsys):
-    check_y2038_safe('./addons/test/y2038/y2038-test-1-bad-time-bits.c.dump', quiet=True)
+    is_safe = check_y2038_safe('./addons/test/y2038/y2038-test-1-bad-time-bits.c.dump', quiet=True)
+    assert(is_safe is False)
     captured = capsys.readouterr()
     captured = captured.out.splitlines()
     json_output = convert_json_output(captured)
@@ -50,7 +52,8 @@ def test_1_bad_time_bits(capsys):
 
 
 def test_2_no_time_bits(capsys):
-    check_y2038_safe('./addons/test/y2038/y2038-test-2-no-time-bits.c.dump', quiet=True)
+    is_safe = check_y2038_safe('./addons/test/y2038/y2038-test-2-no-time-bits.c.dump', quiet=True)
+    assert(is_safe is False)
     captured = capsys.readouterr()
     captured = captured.out.splitlines()
     json_output = convert_json_output(captured)
@@ -66,7 +69,8 @@ def test_2_no_time_bits(capsys):
 
 
 def test_3_no_use_time_bits(capsys):
-    check_y2038_safe('./addons/test/y2038/y2038-test-3-no-use-time-bits.c.dump', quiet=True)
+    is_safe = check_y2038_safe('./addons/test/y2038/y2038-test-3-no-use-time-bits.c.dump', quiet=True)
+    assert(is_safe is False)
     captured = capsys.readouterr()
     captured = captured.out.splitlines()
     json_output = convert_json_output(captured)
@@ -77,7 +81,8 @@ def test_3_no_use_time_bits(capsys):
 
 
 def test_4_good(capsys):
-    check_y2038_safe('./addons/test/y2038/y2038-test-4-good.c.dump', quiet=True)
+    is_safe = check_y2038_safe('./addons/test/y2038/y2038-test-4-good.c.dump', quiet=True)
+    # assert(is_safe is True) # FIXME: This should be a "good" example returning "True" instead of "False"
     captured = capsys.readouterr()
     captured = captured.out.splitlines()
     json_output = convert_json_output(captured)
@@ -88,6 +93,19 @@ def test_4_good(capsys):
     assert(len([c for c in unsafe_calls if c['file'].endswith('.c')]) == 0)
 
 
+def test_5_good(capsys):
+    is_safe = check_y2038_safe('./addons/test/y2038/y2038-test-5-good-no-time-used.c.dump', quiet=True)
+    assert(is_safe is True)
+    captured = capsys.readouterr()
+    captured = captured.out.splitlines()
+    json_output = convert_json_output(captured)
+
+    # There are no warnings from C sources.
+    if 'unsafe-call' in json_output:
+        unsafe_calls = json_output['unsafe-call']
+        assert(len([c for c in unsafe_calls if c['file'].endswith('.c')]) == 0)
+
+
 def test_arguments_regression():
     args_ok = ["-t=foo", "--template=foo",
                "-q", "--quiet",

addons/test/y2038/y2038-test-5-good-no-time-used.c

@@ -0,0 +1,14 @@
+/*
+ * C file that does not use any time functionality -> no errors should
+ * be reported.
+ */
+
+#include <stdio.h>
+
+int main(int argc, char **argv)
+{
+    if (argc > 1) {
+        printf("Hello");
+    }
+    return 0;
+}

addons/y2038.py

@@ -151,8 +151,8 @@ id_Y2038 = {
 
 
 def check_y2038_safe(dumpfile, quiet=False):
-    # at the start of the check, we don't know if code is Y2038 safe
-    y2038safe = False
+    # Assume that the code is Y2038 safe until proven otherwise
+    y2038safe = True
     # load XML from .dump file
     data = cppcheckdata.parsedump(dumpfile)