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Comment by rolandhvar | Hacker News Reader

The thing that always irks me about c++ is this sort of thing:

> Explanation 1) Searches for the resource identified by h-char-sequence in implementation-defined manner.

Okay, so now I have to make assumptions that the implementation is reasonable, and won't go and "search" by asking an LLM or accidentally revealing my credit card details to a third party, right?

And even if the implementation _is_ reasonable the only way I know what "search" means in this context is by looking at an example, and the example says "it's basically a filename".

So now I think to myself: if I want to remain portable, I'll just write a python script to do a damn substitution to embed my file, which is guaranteed to work under _any_ implementation and I don't have to worry about it as soon as I have my source file.

Does anyone else feel this way or is it just me?

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You're not the only one who feels that way, but IMHO it's not a valid complaint.

The C++ standard says implementation defined because the weeds get very thick very quickly:

- Are paths formed with forward slash or backslash?

- Case sensitive?

- NT style drive letter or Posix style mounts?

- For relative paths, what is it relative to? When there are multiple matches, what is the algorithm to determine priority?

- What about symlinks and hard links?

- Are http and ftp URIs supported (e.g. an online IDE like godbolt). If so, which versions of those protocols? TLS 1.3+ only? Are you going to accept SHA-1?

- Should the file read be transactional?

People already complain that the C++ standard is overly complicated. So instead of adding even more complexity by redefining the OS semantics of your build platform in a language spec, they use "implementation defined" as a shorthand for "your compiler will call fopen" plus some implementation wiggle room like command line options for specifying search paths and the strategy for long paths on Windows

What if #embed steals my credit card data is a pointless strawman. If a malicious compiler dev wanted to steal your credit card data, they'd just inject the malicious code; not act like a genie, searching the C++ spec with a fine comb for a place where they could execute malicious code while still *technically* being standards conformant. You know that, I know that, we all know that. So why are we wasting words discussing it?

Including files also opens up some potential security issues that the standards committee just didn't want to prescribe solutions to. Compiler explorer hides easter eggs around the virtual filesystem, for example:

https://godbolt.org/z/KcqTM5bTr

The real reason why this stuff in underspecified in the spec is that some mainframe operating systems don't have file systems in the common modern sense, but support C++. Those vendors push back a lot against narroed definitions as far as I know.

#include also searches for the file you give it in an "implementation-defined manner", so if you have this complaint about #embed, you ought to also consider #include equally problematic

> So now I think to myself: if I want to remain portable, I'll just write a python script

How can you know that your Python implementation won't send your credit card details to an LLM when it runs your script? It does not follow an ISO standard that says it can't do that. You're not making assumptions about it's behavior, are you?

This doesn't sound like the kind of portability anyone is really worried about. I get that the docs on the linked site are written in standards-ese and are complicated by macro replacement, but I don't think the outcome of sending your credit card details away is gonna be an outcome. If it was, an uncharitable implementation with access to your card details would be free to do that any time you gave it input invoking undefined behaviour (which is of course not uncommon, especially in incorrect code).

which makes me consider an interesting distinction, undefined behavior refers to the behavior of the compiler output, does the C standard "allow" compilers to do compile-time code executions with undefined behavior? is the runtime behavior of the compiler even in scope for the standard in general?

If you want to remain portable, write your code in the intersection of the big 3 - GCC, Clang and MSVC - and you’ll be good enough. Other implementations will either be weird enough that many things you’d expect to work won’t or are forced to copy what those 3 do anyway.

This is what I have been doing for years. Works well for me.

Sometimes it is annoying but realistically it is a good strategy.

...what? What are you talking about? In what world would a compiler implement a preprocessor directive to ever use an llm, the internet, or your credit card details (from where would it get those)??? There are always implementation defined things in every language, for example, ub behavior. Do you get worried that someone will steal your bitcoin every time you use after free? Of course not! Even in Python when you OOM -- at least in CPython -- you crash with undefined behavior.

Sorry for being so aggressive. I suppose I'm just very confused at where you're coming from.

this take is basically equivalent to "don't write software unless you write the stack from scratch."

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