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Some modules and unit tests use exceptions, e.g. the riot::thread implementation from the cpp11_compat module and the according unit test.
Steps to reproduce the issue
I've created a unit test to demonstrate the current undefined behavior: jenswet@7940cbe
Expected results
All boards should give the following result:
************ C++ exception test ***********
Exceptions enabled
Exception catched
******************************************
Actual results
The native board does as expected:
RIOT native board initialized.
RIOT native hardware initialization complete.
Help: Press s to start test, r to print it is ready
READY
s
START
main(): This is RIOT! (Version: 2022.04-devel-20-g95b50-cpp-exception)
************ C++ exception test ***********
Exceptions enabled
Exception catched
******************************************
The nucleo-f767zi does the following (with both gnu and llvm toolchain):
main(): This is RIOT! (Version: 2022.04-devel-20-g95b50-cpp-exception)
************ C++ exception test ***********
Exceptions enabled
#! exit 1: powering off
With the default compiler flags there is no-fno-exceotions.
When adding -fno-exceotions manually and therefore disabling exceptions the test wouldn't even compile:
tests/cpp_exception/main.cpp:26:6: error: '__EXCEPTIONS' was not declared in this scope
26 | if(__EXCEPTIONS) {
| ^~~~~~~~~~~~
tests/cpp_exception/main.cpp:38:43: error: exception handling disabled, use '-fexceptions' to enable
38 | throw std::runtime_error("Exception");
| ^
tests/cpp_exception/main.cpp:41:30: error: 'e' was not declared in this scope
41 | printf("%s catched\n", e.what());
| ^
Exact the same behavior can be verified on esp32-wroom-32:
************ C++ exception test ***********
Exceptions enabled
#! exit 1: powering off
The devices are powered off instead of catching the exception.
Arduino has defined behabior, when trying to compile code that uses exceptions an error occurs error: exception handling disabled, use -fexceptions to enable.
I didn't try the other platforms because of missing hardware.
I don't want to discuss whether exceptions are useful for embedded development or not. But the behavior should be consistent. Either they should work or they should be disabled. When they do not work, they should not be used in any module imho.
Versions
It doesn't matter whether I build locally:
Operating System Environment
----------------------------
Operating System: macOS 11.6.2
Kernel: Darwin 20.6.0 x86_64 i386
./dist/tools/ci/print_toolchain_versions.sh: line 78: realpath: command not found
System shell: (probably dash)
make's shell: GNU bash, version 3.2.57(1)-release (x86_64-apple-darwin20)
Installed compiler toolchains
-----------------------------
native gcc: gcc (Homebrew GCC 10.2.0_4) 10.2.0
arm-none-eabi-gcc: arm-none-eabi-gcc (GNU Arm Embedded Toolchain 9-2020-q2-update) 9.3.1 20200408 (release)
avr-gcc: avr-gcc (Homebrew AVR GCC 9.3.0_3) 9.3.0
mips-mti-elf-gcc: missing
msp430-elf-gcc: missing
riscv-none-elf-gcc: missing
riscv64-unknown-elf-gcc: missing
riscv-none-embed-gcc: missing
xtensa-esp32-elf-gcc: xtensa-esp32-elf-gcc (crosstool-NG crosstool-ng-1.22.0-61-gab8375a) 5.2.0
xtensa-esp8266-elf-gcc: missing
clang: Apple clang version 13.0.0 (clang-1300.0.29.30)
Installed compiler libs
-----------------------
arm-none-eabi-newlib: "3.3.0"
mips-mti-elf-newlib: missing
msp430-elf-newlib: missing
riscv-none-elf-newlib: missing
riscv64-unknown-elf-newlib: missing
riscv-none-embed-newlib: missing
xtensa-esp32-elf-newlib: "2.2.0"
xtensa-esp8266-elf-newlib: missing
avr-libc: "2.0.0" ("20150208")
Installed development tools
---------------------------
ccache: missing
cmake: cmake version 3.21.0
cppcheck: missing
doxygen: 1.9.1
git: git version 2.32.0 (Apple Git-132)
make: GNU Make 4.3
openocd: Open On-Chip Debugger 0.10.0+dev-01514-ga8edbd020-dirty (2020-11-30-10:23)
python: Python 2.7.16
python2: Python 2.7.16
python3: Python 3.9.7
flake8: error: /usr/local/opt/python@3.9/bin/python3.9: No module named flake8
coccinelle: missing
or with the latest riot/riotbuild.
The text was updated successfully, but these errors were encountered:
$ DISABLE_MODULE=newlib_nano BOARD=nucleo-f767zi make -C tests/cpp_exception flash test
[...]
text data bss dec hex filename
70312 2512 2488 75312 12630 /home/maribu/Repos/software/RIOT/tests/cpp_exception/bin/nucleo-f767zi/tests_cpp_exception.elf
[...]
Help: Press s to start test, r to print it is ready
START
main(): This is RIOT! (Version: 2022.01-devel-1612-gf7dd0-tests/cpp11_exceptions)
************ C++ exception test ***********
Exceptions enabled
Exception catched
******************************************
I'm pulling the current version of riot/riotbuild to confirm this behavior for non-Alpine systems. But it looks like -fno-exceptions has to be added when using newlib_nano.
It would also be sensible to prominently document that adding DISABLE_MODULE += newlib_nano would enable exceptions. It is also worth pointing out that the non-nano variant buys in a lot of unrelated bloat (such as even more insanely bloated stdio than for newlib_nano) that likely nobody wants. I think most C++ developers would profit from a nano but with exceptions version of newlib.
OK, with riot/riotbuild there are no exceptions even with DISABLE_MODULE=newlib_nano. Would be nice to know if the Arch Linux toolchain is similar to Alpine in this regard.
I was also trying to give picolibc a try, but that doesn't seem to work at all with C++. (Generally speaking, picolibc is the better and more active C lib and RIOT is very likely to switch there, when the remaining issues are solved. That might also be chance to get C++ support right even without buying in bloat.)
maribu
added
the
Type: bug
The issue reports a bug / The PR fixes a bug (including spelling errors)
label
May 22, 2023
Description
The exception handling is undefined in RIOT.
Some modules and unit tests use exceptions, e.g. the
riot::thread
implementation from thecpp11_compat
module and the according unit test.Steps to reproduce the issue
I've created a unit test to demonstrate the current undefined behavior: jenswet@7940cbe
Expected results
All boards should give the following result:
Actual results
The native board does as expected:
The
nucleo-f767zi
does the following (with bothgnu
andllvm
toolchain):With the default compiler flags there is no
-fno-exceotions
.When adding
-fno-exceotions
manually and therefore disabling exceptions the test wouldn't even compile:Exact the same behavior can be verified on
esp32-wroom-32
:The devices are powered off instead of catching the exception.
Arduino has defined behabior, when trying to compile code that uses exceptions an error occurs
error: exception handling disabled, use -fexceptions to enable
.I didn't try the other platforms because of missing hardware.
I don't want to discuss whether exceptions are useful for embedded development or not. But the behavior should be consistent. Either they should work or they should be disabled. When they do not work, they should not be used in any module imho.
Versions
It doesn't matter whether I build locally:
or with the latest
riot/riotbuild
.The text was updated successfully, but these errors were encountered: