Hacker News Reader

Comment by simonask | Hacker News Reader

Excuse me, what? I was writing both C and C++ 20 years ago, and UB was a huge part of the conversation (and the curriculum) back then as well.

There were a few high-profile "scandals" around GCC 3.2 (IIRC) because the compiler finally started much more aggressively using UB in optimizations, which was a reason that lots of people stayed on GCC 2.95 for a very long time. GCC 3.2 came out in 2002.

View on HN

Started in 2005. Never ever did anyone complain about UB in my years of writing C code and patching other people's C code. I knew it exists - as a spec quirk. (Admittedly, never wrote a compiler and never used anything except gcc and clang.)

“More aggressively using UB” isn’t the right way to think about it.

In the C ecosystem, the compiler gets to define what UB means. They broke compatibility with their previous UB semantics, then blamed the language spec.

> In the C ecosystem, the compiler gets to define what UB means.

It really doesn't though. The current revision of the ISO/IEC 9899 standards document gets to define it, nobody else.

No; that says what things have undefined behavior in the language spec.

The compiler / os / hw platform are free to define the behavior of those things. Leaving them undefined at the language spec is the mechanism that allows them to be defined by the underlying system. C has worked this way since its initial release.

Reply on news.ycombinator.com