boards: unit_testing + native_sim/native: time_t incompatible with all other platforms

[cfriedt]

Describe the bug

While creating some additional utilities for dealing with time structures, and using the unit_testing board (since that is the least expensive of all of our test platforms), I was triggering an unexpected assertion.

Namely:

BUILD_ASSERT(sizeof(((struct timespec *)0)->tv_sec) == sizeof(int64_t), "tv_sec must be 64-bit");

Just to be sure that this was out of the ordinary, I created a testsuite to check that time_t was 64-bit on all other platforms (see 'Additional Context'), and sure enough, every other architecture that is supported by Zephyr supports a 64-bit time_t,
except for unit_testing and native_sim/native (the 32-bit variant of native_sim/native/64).

I realize it's a bit tricky due to the current -m32 CFLAG, and what that might imply for the host platform in terms of other standard C types if we were to move to -m64 instead.

However, we typically do want to test both 64-bit and 32-bit platforms with our unit_testing platform, and for the most part, standard C types should be compatible between our unit_testing platform and all other Zephyr platforms.

Please also mention any information which could help others to understand
the problem you're facing:

• What target platform are you using? unit_testing, native_sim/native (and all other architectures)
• What have you tried to diagnose or workaround this issue? Compared with every other architecture supported by Zephyr
• Is this a regression? Unsure

To Reproduce

1. create basic testsuites with the added items below
2. twister -i -p unit_testing -T tests/unit/timeutil
3. See error
4. run contrived non-unit-testing testsuite below
5. See success (inconsistence)

Expected behavior
That standard C types should be consistent between the unit_testing platform and all other platforms in Zephyr.

Impact
The impact to the utilities and testsuite that I'm working on is pretty big, since it should cover most possible values within the [INT64_MIN, INT64_MAX] range, but without the support of the unit_testing platform itself,

Logs and console output

west build -p auto -b unit_testing -t run tests/unit/timeutil/
...
In file included from /home/cfriedt/zephyrproject/zephyr/include/zephyr/toolchain.h:52,
                 from /home/cfriedt/zephyrproject/zephyr/include/zephyr/sys/printk.h:11,
                 from /home/cfriedt/zephyrproject/zephyr/subsys/testsuite/ztest/include/zephyr/ztest.h:37,
                 from /home/cfriedt/zephyrproject/zephyr/tests/unit/timeutil/test_timespec.c:12:
/home/cfriedt/zephyrproject/zephyr/include/zephyr/toolchain/gcc.h:87:36: error: static assertion failed: "tv_sec must be 64-bit"
   87 | #define BUILD_ASSERT(EXPR, MSG...) _Static_assert((EXPR), "" MSG)
      |                                    ^~~~~~~~~~~~~~
/home/cfriedt/zephyrproject/zephyr/include/zephyr/sys/timespec_util.h:23:1: note: in expansion of macro ‘BUILD_ASSERT’
   23 | BUILD_ASSERT(sizeof(((struct timespec *)0)->tv_sec) == sizeof(int64_t), "tv_sec must be 64-bit");

twister -i -T tests/lib/time_t/
...
ERROR   - native_sim/native         tests/lib/time_t/libraries.time_t.size             ERROR: Build failure
...
ccache /usr/lib/ccache/gcc -DKERNEL -DK_HEAP_MEM_POOL_SIZE=0 -DTC_RUNID=071b3a4d2ea8804c8fa5ef11ea55afa5 -D__ZEPHYR__=1 -I/home/cfriedt/zephyrproject/zephyr/twister-out/native_sim_native/host/tests/lib/time_t/libraries.time_t.size/zephyr/include/generated/zephyr -I/home/cfriedt/zephyrproject/zephyr/include -I/home/cfriedt/zephyrproject/zephyr/twister-out/native_sim_native/host/tests/lib/time_t/libraries.time_t.size/zephyr/include/generated -I/home/cfriedt/zephyrproject/zephyr/soc/native/inf_clock -I/home/cfriedt/zephyrproject/zephyr/boards/native/native_sim -I/home/cfriedt/zephyrproject/zephyr/scripts/native_simulator/common/src/include -I/home/cfriedt/zephyrproject/zephyr/scripts/native_simulator/native/src/include -I/home/cfriedt/zephyrproject/zephyr/subsys/testsuite/include -I/home/cfriedt/zephyrproject/zephyr/subsys/testsuite/coverage -I/home/cfriedt/zephyrproject/zephyr/subsys/testsuite/ztest/include -fno-strict-aliasing -Werror -Os -imacros /home/cfriedt/zephyrproject/zephyr/twister-out/native_sim_native/host/tests/lib/time_t/libraries.time_t.size/zephyr/include/generated/zephyr/autoconf.h -fno-common -g -gdwarf-4 -fdiagnostics-color=always -Wall -Wformat -Wformat-security -Wno-format-zero-length -Wdouble-promotion -Wno-pointer-sign -Wpointer-arith -Wexpansion-to-defined -Wno-unused-but-set-variable -Werror=implicit-int -fno-pic -fno-pie -fno-asynchronous-unwind-tables -fno-reorder-functions --param=min-pagesize=0 -fno-defer-pop -fmacro-prefix-map=/home/cfriedt/zephyrproject/zephyr/tests/lib/time_t=CMAKE_SOURCE_DIR -fmacro-prefix-map=/home/cfriedt/zephyrproject/zephyr=ZEPHYR_BASE -fmacro-prefix-map=/home/cfriedt/zephyrproject=WEST_TOPDIR -ffunction-sections -fdata-sections -m32 -msse2 -mfpmath=sse -fvisibility=hidden -fno-freestanding -std=c11 -MD -MT CMakeFiles/app.dir/src/main.c.obj -MF CMakeFiles/app.dir/src/main.c.obj.d -o CMakeFiles/app.dir/src/main.c.obj -c /home/cfriedt/zephyrproject/zephyr/tests/lib/time_t/src/main.c
In file included from /home/cfriedt/zephyrproject/zephyr/include/zephyr/toolchain.h:52,
                 from /home/cfriedt/zephyrproject/zephyr/include/zephyr/sys/util.h:18,
                 from /home/cfriedt/zephyrproject/zephyr/include/zephyr/sys_clock.h:19,
                 from /home/cfriedt/zephyrproject/zephyr/include/zephyr/sys/timespec_util.h:15,
                 from /home/cfriedt/zephyrproject/zephyr/tests/lib/time_t/src/main.c:4:
/home/cfriedt/zephyrproject/zephyr/include/zephyr/toolchain/gcc.h:87:36: error: static assertion failed: "tv_sec must be 64-bit"
   87 | #define BUILD_ASSERT(EXPR, MSG...) _Static_assert((EXPR), "" MSG)
      |                                    ^~~~~~~~~~~~~~
/home/cfriedt/zephyrproject/zephyr/include/zephyr/sys/timespec_util.h:23:1: note: in expansion of macro ‘BUILD_ASSERT’
   23 | BUILD_ASSERT(sizeof(((struct timespec *)0)->tv_sec) == sizeof(int64_t), "tv_sec must be 64-bit");
      | ^~~~~~~~~~~~
/home/cfriedt/zephyrproject/zephyr/include/zephyr/toolchain/gcc.h:87:36: error: static assertion failed: "tv_sec must be 64-bit"
   87 | #define BUILD_ASSERT(EXPR, MSG...) _Static_assert((EXPR), "" MSG)
      |                                    ^~~~~~~~~~~~~~
/home/cfriedt/zephyrproject/zephyr/tests/lib/time_t/src/main.c:7:1: note: in expansion of macro ‘BUILD_ASSERT’
    7 | BUILD_ASSERT(sizeof(((struct timespec *)0)->tv_sec) == sizeof(int64_t), "tv_sec must be 64-bit");
      | ^~~~~~~~~~~~

Environment (please complete the following information):

• OS: Linux
• Toolchain: Zephyr SDK v0.17.0
• Commit SHA: 4512cbf

Additional context
basic testcase.yml for the unit_testing platform and the test_timeutil.c below (and added to tests/unit/timeutil/CMakeLists.txt).

tests/unit/timeutil/test_timeutil.c:

BUILD_ASSERT(sizeof(((struct timespec *)0)->tv_sec) == sizeof(int64_t), "tv_sec must be 64-bit");

When the same .c file is run through a non-unit_testing testsuite (tests/lib/time_t/) with the testcase.yml file below, all other platforms pass except for unit_testing and native_sim/native, even in contrast to other 32-bit platforms.

testcase.yaml

common:
  tags:
    - libc
  # 1 tier0 platform per supported architecture
  platform_key:
    - arch
    - simulation
tests:
  libraries.time_t.size: {}
  libraries.time_t.size.armclang_std_libc:
    toolchain_allow: armclang
    extra_configs:
      - CONFIG_ARMCLANG_STD_LIBC=y
  libraries.time_t.size.arcmwdtlib:
    toolchain_allow: arcmwdt
    extra_configs:
      - CONFIG_ARCMWDT_LIBC=y
  libraries.time_t.size.minimal:
    extra_configs:
      - CONFIG_MINIMAL_LIBC=y
  libraries.time_t.size.newlib:
    filter: TOOLCHAIN_HAS_NEWLIB == 1
    extra_configs:
      - CONFIG_NEWLIB_LIBC=y
  libraries.time_t.size.picolibc:
    tags: picolibc
    filter: CONFIG_PICOLIBC_SUPPORTED
    extra_configs:
      - CONFIG_PICOLIBC=y

[cfriedt]

Just to unblock myself, I might move the test to a non-unit_testing testsuite, and add native_sim/native in platform_exclude.

It's also possible to filter using filter: not CONFIG_NATIVE_APPLICATION or filter: not CONFIG_NATIVE_LIBC, but I'm hoping there is another way to ensure that time_t is 64-bit everywhere, and then also move the testsuite to tests/unit/timeutil

[cfriedt]

Ah, just realized this is a known issue that is still not completely solved in Linux distributions.

Definitely not going to be solved overnight. I guess it maybe helps to keep the ticket here?