Am 26.10.2019 um 18:51 schrieb J. Gareth Moreton:
The "const" suggestion was made by a third party, and while I went out of my way to ensure the functions aren't changed in Pascal code, Florian pointed out that it could break existing assembler code. Maybe I'm being a bit stubborn or unreasonable, I'm not sure, but in my eyes, using assembly language to directly call the uComplex functions and operators seems rather unrealistic. I figured if you're writing in assembly language, especially if you're using vector registers, you'd be using your own code to play around with complex numbers. Plus I figured that if you're developing on a non-x86_64 platform, the only thing that's different are the 'const' modifiers, which I don't think changes the way you actually call the function, regardless of platform. Am I right in this?
It totally depends on how "const" is implemented for the particular target. On some there might not be any difference on others there might be a similar difference as for x86, namely that something is passed as a reference instead of a copy.
I guess a more fundamental question I should ask, and this might be terribly naïve of me, is this: when you call some function F(x: TType), is there a situation where calling F(const x: TType) produces different machine code or where a particular actual parameter becomes illegal? Note I'm talking about how you call the function, not how the function itself is compiled.
Didn't you provide the example yourself with your changes to the uComplex unit? There are cases (especially with records) where "x" is passed as a copy on the stack and "const x" is passed as a reference.
Regards, Sven _______________________________________________ fpc-devel maillist - fpc-devel@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel
