Can't compile with GCC 7.1.1

[Rubonnek]

Compiling latest release (v1.5.3) or the latest git commit 00d5e22 yields the following:

...
[ 72%] Building C object tests/CMakeFiles/parse_with_opts.dir/parse_with_opts.c.o
In file included from /path_to_src/cJSON-1.5.3/tests/unity/src/unity.h:16:0,
                 from /path_to_src/cJSON-1.5.3/tests/parse_hex4.c:28:
/path_to_src/cJSON-1.5.3/tests/parse_hex4.c: In function ‘parse_hex4_should_parse_all_combinations’:
/path_to_src/cJSON-1.5.3/tests/parse_hex4.c:39:42: error: ‘sprintf’ may write a terminating nul past the end of the destination [-Werror=format-overflow=]
         TEST_ASSERT_EQUAL_INT_MESSAGE(4, sprintf((char*)digits_lower, "%.4x", number), "sprintf failed.");
/path_to_src/cJSON-1.5.3/tests/unity/src/unity_internals.h:640:156: note: in definition of macro ‘UNITY_TEST_ASSERT_EQUAL_INT’
 #define UNITY_TEST_ASSERT_EQUAL_INT(expected, actual, line, message)                             UnityAssertEqualNumber((UNITY_INT)(expected), (UNITY_INT)(actual), (message), (UNITY_LINE_TYPE)(line), UNITY_DISPLAY_STYLE_INT)
                                                                                                                                                            ^~~~~~
/path_to_src/cJSON-1.5.3/tests/parse_hex4.c:39:9: note: in expansion of macro ‘TEST_ASSERT_EQUAL_INT_MESSAGE’
         TEST_ASSERT_EQUAL_INT_MESSAGE(4, sprintf((char*)digits_lower, "%.4x", number), "sprintf failed.");
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/path_to_src/cJSON-1.5.3/tests/parse_hex4.c:39:42: note: ‘sprintf’ output between 5 and 6 bytes into a destination of size 5
         TEST_ASSERT_EQUAL_INT_MESSAGE(4, sprintf((char*)digits_lower, "%.4x", number), "sprintf failed.");
/path_to_src/cJSON-1.5.3/tests/unity/src/unity_internals.h:640:156: note: in definition of macro ‘UNITY_TEST_ASSERT_EQUAL_INT’
 #define UNITY_TEST_ASSERT_EQUAL_INT(expected, actual, line, message)                             UnityAssertEqualNumber((UNITY_INT)(expected), (UNITY_INT)(actual), (message), (UNITY_LINE_TYPE)(line), UNITY_DISPLAY_STYLE_INT)
                                                                                                                                                            ^~~~~~
/path_to_src/cJSON-1.5.3/tests/parse_hex4.c:39:9: note: in expansion of macro ‘TEST_ASSERT_EQUAL_INT_MESSAGE’
         TEST_ASSERT_EQUAL_INT_MESSAGE(4, sprintf((char*)digits_lower, "%.4x", number), "sprintf failed.");
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/path_to_src/cJSON-1.5.3/tests/parse_hex4.c:40:42: error: ‘sprintf’ may write a terminating nul past the end of the destination [-Werror=format-overflow=]
         TEST_ASSERT_EQUAL_INT_MESSAGE(4, sprintf((char*)digits_upper, "%.4X", number), "sprintf failed.");
/path_to_src/cJSON-1.5.3/tests/unity/src/unity_internals.h:640:156: note: in definition of macro ‘UNITY_TEST_ASSERT_EQUAL_INT’
 #define UNITY_TEST_ASSERT_EQUAL_INT(expected, actual, line, message)                             UnityAssertEqualNumber((UNITY_INT)(expected), (UNITY_INT)(actual), (message), (UNITY_LINE_TYPE)(line), UNITY_DISPLAY_STYLE_INT)
                                                                                                                                                            ^~~~~~
/path_to_src/cJSON-1.5.3/tests/parse_hex4.c:40:9: note: in expansion of macro ‘TEST_ASSERT_EQUAL_INT_MESSAGE’
         TEST_ASSERT_EQUAL_INT_MESSAGE(4, sprintf((char*)digits_upper, "%.4X", number), "sprintf failed.");
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/path_to_src/cJSON-1.5.3/tests/parse_hex4.c:40:42: note: ‘sprintf’ output between 5 and 6 bytes into a destination of size 5
         TEST_ASSERT_EQUAL_INT_MESSAGE(4, sprintf((char*)digits_upper, "%.4X", number), "sprintf failed.");
/path_to_src/cJSON-1.5.3/tests/unity/src/unity_internals.h:640:156: note: in definition of macro ‘UNITY_TEST_ASSERT_EQUAL_INT’
 #define UNITY_TEST_ASSERT_EQUAL_INT(expected, actual, line, message)                             UnityAssertEqualNumber((UNITY_INT)(expected), (UNITY_INT)(actual), (message), (UNITY_LINE_TYPE)(line), UNITY_DISPLAY_STYLE_INT)
                                                                                                                                                            ^~~~~~
/path_to_src/cJSON-1.5.3/tests/parse_hex4.c:40:9: note: in expansion of macro ‘TEST_ASSERT_EQUAL_INT_MESSAGE’
         TEST_ASSERT_EQUAL_INT_MESSAGE(4, sprintf((char*)digits_upper, "%.4X", number), "sprintf failed.");
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~

[FSMaxB]

I can't reproduce this using GCC 7.1.1 on Archlinux x86_64. Can you please provide some information about your build environment.

[Rubonnek]

I'm also using Archlinux x86_64. I just updated all the packages today. I also removed /etc/makepkg.conf and reinstalled a default one, and I still got that same message.

[Rubonnek]

By the way, I tried installing it using the packages cjson and cjson-git from the AUR.

[FSMaxB]

That's strange, when building from the AUR I get the same error. I'll investigate!

[Rubonnek]

Whoa, you're right. I just cloned the repository and I was able to build it manually, but building through the AUR doesn't work.

[FSMaxB]

I found the reason: The build only fails when compiling with -O2 (or possibly other optimization levels), which makepkg sets by default.

Should be an easy fix, just checking for format-overlow support and disabling it and reporting the issue with cUnity upstream (if it's not already fixed).

Working on it!

[FSMaxB]

Fixed and AUR packages updated! Thanks for reporting.

I'm still not sure though why GCC was complaining, this shouldn't be an overflow, maybe I have to file a bug.

[Rubonnek]

Thanks a lot!