3 ms·

> at worst nonsensical (always_inline with noinline?!) I think this is actually great support for their thesis. If you came across actual code that looked lik

> at worst nonsensical (always_inline with noinline?!) I think this is actually great support for their thesis. If you came across actual code that looked like that (and god knows it probably exists if it's legal), who fucking knows what the compiler would do? My question is: why is it even legal to mark functions with both of these, in addition to the `inline` keyword? My guess is the C++ spec says something along the lines of "you can mark functions with as many attributes as you want .. something .. something .." ie compiler vendors get no choice but to (at best) emit a warning.

Joker_vD 4y ago
> god knows it probably exists if it's legal It most certainly exists, even if it's actually illegal. I mean, come on, how many are there C codebases with more than 10k lines that have absolutely zero UB? I've seen several C programmers who, when "wrestling the compiler" to emit some certain kind of pattern in the resulting assembly, would do bloody anything without much regard whether what they wrote was legal, or implementation-specific, or UB. "It compiles to what I want with the compiler we use today, that's all that matters. We'll probably change it in the future if it breaks".
gpderetta 4y ago
the no_inline attribute is non-standard, so the C++ standard has nothing say about it. In C++ marking an inline function no_inline is actually meaningful: the inline specifier has little to do with actually performing the inlining optimization and for the most part it means that the ODR rules are weakened (in practice enabling vague linkage). The no_inline attribute instead prevents the optimization from occurring. So an inline no_inline function is a function with vague linkage that should not be inlined. As it allows the function to be defined in an header file and usually a function body need to be available in a translation unit, functions that should be inlined are often marked as inline (which also acts as a weak hint to the optimizer), but it is neither necessary nor sufficient. And the naming is of course for the most part historical.
- jesse__ 4y ago
  This is great context, thanks for the reply.

Joker_vD 4y ago

> god knows it probably exists if it's legal It most certainly exists, even if it's actually illegal. I mean, come on, how many are there C codebases with more than 10k lines that have absolutely zero UB? I've seen several C programmers who, when "wrestling the compiler" to emit some certain kind of pattern in the resulting assembly, would do bloody anything without much regard whether what they wrote was legal, or implementation-specific, or UB. "It compiles to what I want with the compiler we use today, that's all that matters. We'll probably change it in the future if it breaks".

gpderetta 4y ago

the no_inline attribute is non-standard, so the C++ standard has nothing say about it. In C++ marking an inline function no_inline is actually meaningful: the inline specifier has little to do with actually performing the inlining optimization and for the most part it means that the ODR rules are weakened (in practice enabling vague linkage). The no_inline attribute instead prevents the optimization from occurring. So an inline no_inline function is a function with vague linkage that should not be inlined. As it allows the function to be defined in an header file and usually a function body need to be available in a translation unit, functions that should be inlined are often marked as inline (which also acts as a weak hint to the optimizer), but it is neither necessary nor sufficient. And the naming is of course for the most part historical.

jesse__ 4y ago
This is great context, thanks for the reply.