0.30000000000000004 VS gcc

This is due to the way floating point numbers are represented in memory, certain numbers like 0.3 are stored as a number very close to the original value (0.30000000000000004), but not the exact same. This problem also exists in other languages like JavaScript and C++, but is much more likely to cause problems in common applications of Python like machine learning and data science.

https://0.30000000000000004.com/

Although it would be good to move in the direction of using a BigDecimal equivalent by default when ingesting unknown data.

There's no such thing as precision for floats. Floating-point calculations are always inaccurate: read this: https://0.30000000000000004.com/

Edit: This specific example even has its own website: https://0.30000000000000004.com/

> (and of course eventually dropping support for Motorola 68010 on which the Tektronix 4404 is built)

I don't think it ever did? Looking here[1] it still seems to be supported

[1]https://github.com/gcc-mirror/gcc/blob/master/gcc/config/m68...

There are some open source C compilers such as the GNU C compilers (https://github.com/gcc-mirror/gcc) and Clang (https://clang.llvm.org/get_started.html).

There are also proprietary C compilers such as the Microsoft's C compiler (https://visualstudio.microsoft.com/vs/features/cplusplus/) and the Intel C compiler (https://www.intel.com/content/www/us/en/developer/tools/onea...).

There are many others: https://en.m.wikipedia.org/wiki/List_of_compilers#C_compiler...

Most mature C compilers will specify what version(s) of the C standard they implement so developer users can know what features are available. Many C compilers also implement non-standard extensions to the C language and libraries to be more competitive, overcome language shortcomings, or provide for specialized needs or development targets (e.g. features for embedded targets).

But I'm still sure that there are several UB's in my code :)

[1] https://tunglevo.com/note/an-optimization-thats-impossible-i...

[2] https://github.com/gcc-mirror/gcc/blob/d09131eea083e80ccad60...

[3] https://github.com/llvm/llvm-project/blob/4468d58080d0502a05...

I was hoping GCC would do the same, leaving the decision about the value of '\n' to GCC's compiler, but apparently it hardcodes the numeric values for escapes[1], with options for ASCII or EBCDIC systems.

[1] https://github.com/gcc-mirror/gcc/blob/8a4a967a77cb937a2df45...

GCC github-mirror GCC Documentation GCC Internals Mannual Installing GCC

As far as I know, libstdc++'s representation has two advantages:

First, it simplifies the implementation of `s.data()`, because you hold a pointer that invariably points to the first character of the data. The pointer-less version needs to do a branch there. Compare libstdc++ [1] to libc++ [2].

[1]: https://github.com/gcc-mirror/gcc/blob/065dddc/libstdc++-v3/...

[2]: https://github.com/llvm/llvm-project/blob/1a96179/libcxx/inc...

Basically libstdc++ is paying an extra 8 bytes of storage, and losing trivial relocatability, in exchange for one fewer branch every time you access the string's characters. I imagine that the performance impact of that extra branch is tiny, and massively confounded in practice by unrelated factors that are clearly on libc++'s side (e.g. libc++'s SSO buffer is 7 bytes bigger, despite libc++'s string object itself being smaller). But it's there.

The second advantage is that libstdc++ already did it that way, and to change it would be an ABI break; so now they're stuck with it. I mean, obviously that's not an "advantage" in the intuitive sense; but it's functionally equivalent to an advantage, in that it's a very strong technical answer to the question "Why doesn't libstdc++ just switch to doing it libc++'s way?"

Upd: searching in the github mirror by the commit hash from the issue, found that https://github.com/gcc-mirror/gcc/commit/1e3312a25a7b34d6e3f... is in fact in the 'releases/gcc-14.1.0' tag.

Even weirder that this one got swept under the changelog rug, it's a pretty major issue.

> It's true, this was a CVE in Rust and not a CVE in C++, but only because C++ doesn't regard the issue as a problem at all. The problem definitely exists in C++, but it's not acknowledged as a problem, let alone fixed.

Can you find a link that substantiates your claim? You're throwing out some heavy accusations here that don't seem to match reality at all.

Case in point, this was fixed in both major C++ libraries:

https://github.com/gcc-mirror/gcc/commit/ebf6175464768983a2d...

https://github.com/llvm/llvm-project/commit/4f67a909902d8ab9...

So what C++ community refused to regard this as an issue and refused to fix it? Where is your supporting evidence for your claims?