[fpc-devel] XML node dump feature

[J. Gareth Moreton]

While pure and inline do have a lot of overlap and, internally, probably 
share some features for convenience (like a copy of the node tree), they 
are not the same - for example, recursive functions can be pure, but not 
inline, and functions that dereference pointers can be inlined, but not 
made pure.  The constant initialisation is one reason for pure 
functions, as it might be more convenient to declare things like "const 
ONE_OVER_E = Exp(-1);" instead of "const ONE_OVER_E = 
0.36787944117144232159552377016146;" (although Exp might be an intrinsic 
rather than a function - not sure).

Note that while there's room for auto-inlining certain routines, I would 
not recommend "auto-puring" because determining if a function actually 
is pure or not is likely going to be an expensive operation, and it's 
more likely that a function will not be pure.

Gareth aka. Kit

On 25/06/2019 16:31, Ben Grasset wrote:
> On Tue, Jun 25, 2019 at 1:20 AM Sven Barth via fpc-devel 
> <fpc-devel at lists.freepascal.org 
> <mailto:fpc-devel at lists.freepascal.org>> wrote:
>
>     Correct. Though considering that we're talking about *compile
>     time* the
>     compiler *could* treat consts (in {$J-} mode) as constants if pure
>     functions are involved...
>
>
> I'd be fine with the {$J-} requirement (I tend to use {$J-} most of 
> the time anyways, actually.)
>
> Again, I'm aware all of this will take a while to implement, and will 
> be an incremental process. Overall though I think proper compile-time 
> constant initialization needs to be something `pure` eventually 
> enables, as if it doesn't then it just becomes 
> "slightly-different-inlining". (And like denisgolovan pointed out in 
> another message, inlining should remain a separate concept that can be 
> mixed with pure, or not mixed with it, depending on the use case. E.G. 
> a C++ compiler will automatically inline basically anything at -O3, 
> but it will not let you use a non-constexpr function to initialize an 
> actual constexpr value.)
>
> _______________________________________________
> fpc-devel maillist  -  fpc-devel at lists.freepascal.org
> https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel


---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.freepascal.org/pipermail/fpc-devel/attachments/20190625/ae20a211/attachment.html>