The Absurdity of Error Handling: Finding a Purpose for Errors in Safety-Critical SYCL Erik Tomusk CppCon 2023 October 5, 2023© 2023 Codeplay Software Ltd. Codeplay Corporate Slide 2© 2023 Codeplay explicitly stated© 2023 Codeplay Software Ltd. Outline • Definition of Safety • Definition of Error Handling • Case Study • Why is this Important? • Is it Really so bad? • What does this mean for execution time (in mainstream compilers) 17Definition of Error Handling 18© 2023 Codeplay Software Ltd. Definition of Error Handling • Exceptions and error codes are sometimes used for reporting or information

CppCon 2024 Customizing Compilation Error Messages Formatting a Compile-Time String During Substitution Failure Patrick Roberts, P.E. Principal Software Engineer 1CppCon 2024 What problem does solve? 2CppCon 2024 3CppCon 2024 4CppCon 2024 5CppCon 2024 6 Guidelines for a helpful error message Where is the error? ✅ What is wrong? ✅ How can it be fixed? ❌CppCon 2024 7CppCon 2024 8CppCon 2024 9

Modern C++ Handling Phil Nash Error2018 2019series disappointments of a (total) Part 1int parse_int(std::string_view number)// TODO: +, -, digit separators? int acc = 0; for(char c first_digit = false; } return ParseStatus::Numeric; } 42 42 (starts with an int) Error: x42 is not an int test("42"); test("42x"); test("x42"); [[nodiscard]] void test(std::string_view int)”, i); break; case ParseStatus::NonNumeric: std::println(“Error: {} is not an int", str); break; } }int parse_int(std::string_view number) {

Design patterns for error handling in C++ programs using parallel algorithms and executors Mark Hoemmen* mhoemmen@stellarscience.com CppCon 2020 * hoʊ’mən, or hœm’mən; he/himWho am I? • > 10 years 2017 • Started new job at Stellar Science in March Eschew raw pointersOutline • Parallelism makes error handling harder… • …C++ parallel algorithms and tasks specifically • Message Passing Interface (MPI): Responsiveness ILLIAC IV: the 1st massively parallel computer (image: Steve Jurvetson)Parallel hinders error handling • … because parallelism relaxes execution order – Deliberately, to improve performance

leaks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 10.6 Line numbers in run-time error backtraces . . . . . . . . . . . . . . . . . . . . . . . 125 10.7 Combining heaptrc and lineinfo Programmer’s Guide. In the appendices of this document you will find lists of reserved words and compiler error messages (with descriptions). This document describes the compiler as it is/functions at the time • PPC_CONFIG_PATH specifies an alternate path to find the fpc.cfg. • PPC_ERROR_FILE specifies the path and name of the error-definition file. • FPCDIR specifies the root directory of the Free Pascal

std::shared_ptr response) { if (map_.get_data().size() == 0) { RCLCPP_ERROR_STREAM(this->get_logger(), "MAP IS EMPTY!!"); response->code.code = example_srvs::msg::GetPat _OCCUPANCY_MAP; response->path = std_msgs::msg::UInt8MultiArray(); return; } /* More error pre-checks */ auto const start = Position{request->start.data[0], request->start.data[1]}; auto std::shared_ptr response) { if (map_.get_data().size() == 0) { RCLCPP_ERROR_STREAM(this->get_logger(), "MAP IS EMPTY!!"); response->code.code = example_srvs::msg::GetPat

. . . . . . . . . . . . . . 181 1.31 Error codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182 1.32 Error codes enabled by default . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184 1.33 Error codes for optional checks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201 1.34 Additional features whet your appetite: number = input("What is your favourite number?") print("It is", number + 1) # error: Unsupported operand types for + ("str" and "int") Adding type hints for mypy does not interfere

nanos = 0, }; } }; Doc comments are only allowed in certain places; it is a compile error to have a doc comment in an unexpected place, such as in the middle of an expression, or just before @import("std"); Shell $ zig build-obj invalid_doc-comment.zig docgen_tmp/invalid_doc-comment.zig:1:16: error: expected type expression, found 'a docu /// doc-comment ^ unattached_doc-comment file Shell $ zig build-obj unattached_doc-comment.zig docgen_tmp/unattached_doc-comment.zig:3:1: error: unattached documentation comment /// End of file ^~~~~~~~~~~~~~~ Doc comments can be interleaved

. . . . . . . . . . . . . . 182 1.31 Error codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 1.32 Error codes enabled by default . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184 1.33 Error codes for optional checks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202 1.34 Additional features whet your appetite: number = input("What is your favourite number?") print("It is", number + 1) # error: Unsupported operand types for + ("str" and "int") Adding type hints for mypy does not interfere

whet your appetite: number = input("What is your favourite number?") print("It is", number + 1) # error: Unsupported operand types for + ("str" and "int") Adding type hints for mypy does not interfere calls None and Optional handling Configuring warnings Miscellaneous strictness flags Configuring error messages Incremental mode Advanced options Report generation Enabling incomplete/experimental features Optional handling Configuring warnings Suppressing errors Miscellaneous strictness flags Configuring error messages Incremental mode Advanced options Report generation Miscellaneous Using a pyproject.toml