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digitalmars.D - Historic background of std.regex and BacktrackingMatcher

reply Mai Lapyst <mai lapyst.by> writes:
I'm currently working through the dmd (and phobos for that 
matter), and come across it's regex implementation. Here I found 
out it makes rather heavy usage of malloc / pureMalloc; on one 
side to allocate the Matcher implementation inside 
`GenericFactory`; on the other side in `BacktrackingMatcher` for 
memory of it's stack.

Is there any historic reason why it dosnt uses more D-like 
features like `new` or dynamic arrays? It would certainly be 
safer to do so than using an untyped region of memory as 
stack-space.

Also: if it needs "plain" memory; would this code be a good 
candidate to utilize `std.experimental.allocator` once released?

Cheers,
Mai
Oct 05 2023
parent user1234 <user1234 12.de> writes:
On Thursday, 5 October 2023 at 13:36:10 UTC, Mai Lapyst wrote:

 I'm currently working through the dmd (and phobos for that 
 matter), and come across it's regex implementation. Here I 
 found out it makes rather heavy usage of malloc / pureMalloc; 
 on one side to allocate the Matcher implementation inside 
 `GenericFactory`; on the other side in `BacktrackingMatcher` 
 for memory of it's stack.

 Is there any historic reason why it dosnt uses more D-like 
 features like `new` or dynamic arrays? It would certainly be 
 safer to do so than using an untyped region of memory as 
 stack-space.

 Also: if it needs "plain" memory; would this code be a good 
 candidate to utilize `std.experimental.allocator` once released?

 Cheers,
 Mai


Not a formal answers but two clues:

   1. when malloc is used in Phobos it's generally to bypass the GC
   2. std.experimental.allocator was created way after std.regex

Maybe std.regex will see your question and answer more 
accurately. He was active a few weeks ago, coincidentally to 
annouce he had started working on a better design
for a D regex engine 
(https://forum.dlang.org/post/ctdkmvzttmpxwixkmvno forum.dlang.org)
Oct 05 2023