On 11/15/2024 7:22 PM, Andreas Rheinhardt wrote:
James Almer:From: Justine Tunney <jtun...@gmail.com>Header contents taken from https://github.com/jart/jtckdint/commit/62df1fc0966926299253b7af46c777723e345545 Signed-off-by: James Almer <jamr...@gmail.com> --- compat/stdckdint/stdckdint.h | 663 +++++++++++++++++++++++++++++++++++ tests/ref/fate/source | 1 + 2 files changed, 664 insertions(+) create mode 100644 compat/stdckdint/stdckdint.h diff --git a/compat/stdckdint/stdckdint.h b/compat/stdckdint/stdckdint.h new file mode 100644 index 0000000000..2d36e8ad89 --- /dev/null +++ b/compat/stdckdint/stdckdint.h @@ -0,0 +1,663 @@ +/* + * Copyright 2023 Justine Alexandra Roberts Tunney + * + * Permission to use, copy, modify, and/or distribute this software for + * any purpose with or without fee is hereby granted, provided that the + * above copyright notice and this permission notice appear in all copies. + * + * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL + * WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED + * WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE + * AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL + * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR + * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER + * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR + * PERFORMANCE OF THIS SOFTWARE. + */ + +/** + * @fileoverview C23 Checked Arithmetic + * + * This header defines three type generic functions: + * + * - `bool ckd_add(res, a, b)` + * - `bool ckd_sub(res, a, b)` + * - `bool ckd_mul(res, a, b)` + * + * Which allow integer arithmetic errors to be detected. There are many + * kinds of integer errors, e.g. overflow, truncation, etc. These funcs + * catch them all. Here's an example of how it works: + * + * uint32_t c; + * int32_t a = 0x7fffffff; + * int32_t b = 2; + * assert(!ckd_add(&c, a, b)); + * assert(c == 0x80000001u); + * + * Experienced C / C++ users should find this example counter-intuitive + * because the expression `0x7fffffff + 2` not only overflows it's also + * undefined behavior. However here we see it's specified, and does not + * result in an error. That's because C23 checked arithmetic is not the + * arithmetic you're used to. The new standard changes the mathematics. + * + * C23 checked arithmetic is defined as performing the arithmetic using + * infinite precision and then checking if the resulting value will fit + * in the output type. Our example above did not result in an error due + * to `0x80000001` being a legal value for `uint32_t`. + * + * This implementation will use the GNU compiler builtins, when they're + * available, only if you don't use build flags like `-std=c11` because + * they define `__STRICT_ANSI__` and GCC extensions aren't really ANSI. + * Instead, you'll get a pretty good pure C11 and C++11 implementation.Doesn't this imply that we will no longer get the compiler builtins? That is very bad.
Oh, it seems we only set -U__STRICT_ANSI__ on a few targets like mingw, and not all like I assumed. I missed that.
I can remove the relevant check (and this comment) from the header.
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