There's a new keyword in C99, which can be seen as a bad thing. There's also a confusing one-liner which compilers can reduce to a noop and which they can take as the same guarantee as "restrict". One of the most popular compilers sees it as noop but doesn't increase assumptions. Author calls for detection of the one-liner in compilers because he prefers it to the new keyword.
Why doesn't it make sense to me? I'd much rather see restrict than some not googlable magic line. If you're stuck to some old version of a compiler, it's usually (in my experience) because you need some specific architecture support - why not just drop down to asm when you really really need optimised code at that level? Why would you not have C99 support if you're writing for x86_64?
Maybe I'm missing the big idea about specifying pairwise not-aliasing, but can't it be achieved by passing the pointers to another function with restrict attributes instead and ensuring it's inlined?
See also Pascal's followup post, "The previous post was written in jest."[1]
"The previous post assumes the reader is familiar with the notion of undefined behavior and how C compilers have started to justify their more aggressive optimizations along the lines of “this program has always been undefined”....
This was not a serious suggestion, but should be understood as an argument in the debate about the exploitation of undefined behavior in compiler optimization.... I was not suggesting to replace the respected restrict keyword with an awkward replacement. All the arguments I put forward were in bad faith."
There's a new keyword in C99, which can be seen as a bad thing. There's also a confusing one-liner which compilers can reduce to a noop and which they can take as the same guarantee as "restrict". One of the most popular compilers sees it as noop but doesn't increase assumptions. Author calls for detection of the one-liner in compilers because he prefers it to the new keyword.
Why doesn't it make sense to me? I'd much rather see restrict than some not googlable magic line. If you're stuck to some old version of a compiler, it's usually (in my experience) because you need some specific architecture support - why not just drop down to asm when you really really need optimised code at that level? Why would you not have C99 support if you're writing for x86_64?
Maybe I'm missing the big idea about specifying pairwise not-aliasing, but can't it be achieved by passing the pointers to another function with restrict attributes instead and ensuring it's inlined?