DMD path handling is a bit dated, and it's causing build problems
for us because on Windows it's easy to end up breaking DMD's
limit - particularly given how dub likes to turn everything into
a relative path.
Windows has so many beautiful example of the costs of legacy
compat. I just wrote down 5 ways it handles paths, and then
realised there's another. There's a 260 char limit (less a bit,
depending) in the old Windows API, but looking at the ddmd code
there's a more restrictive limit of 131 chars + null for windows
when it builds paths for the base directory.
I think if you use Windows 32 file namespaces (eg
\?\C:\D\foo\bar, and note the difference from \?C\D\foo\bar ) and
the unicode library calls then you get up to 32,767 chars.
We already have much better code in Phobos (for Windows it's
hard-coded at 4K) getcwd, and I think either we should call
Phobos or copy/paste the Phobos function into ddmd.
And I'm posting here because we can submit a pull request, but I
didn't know whether to call Phobos or copy/paste as I haven't
submitted more than trivial doc changes to compiler. I've
written all of this up but on an internal gitlab.
https://github.com/dlang/dmd/blob/2bf9a9d731e88ebd8a175bd0a990a3b651e8df82/src/ddmd/tk/filespec.c
(c) 1986-1987 by NorthWest Software. It could do with an update!
"
So there's an obvious set of related problems. Line 119 -
current working dir is 131 chars + null. and on linux it's
restricted to 255+null (not sure if that limit applies anymore to
linux, but who cares for now).
getcwd prototype is defined here:
https://github.com/dlang/dmd/blob/ebd6606840afea0034ce599815ed950fd558981c/src/ddmd/dmodule.d
and this is the prototype:
extern (C) char* getcwd(char* buffer, size_t maxlen);
it's deprecated and replaced by the ISO function:
https://docs.microsoft.com/en-gb/cpp/c-runtime-library/reference/getcwd-wgetcwd
okay - so:
it's wrong to use that limit on linux and OSX. Linux PATH_MAX is
4096. OpenBSD is 1024. Linux paths are unlimited, apparently
(OSX can have several k chars at least). And the Windows one
should at least be PATH_MAX less a bit even without using long
paths. (But then if you are going to use old winapi need to check
its less than PATH_MAX if you extend).
https://insanecoding.blogspot.co.uk/2007/11/pathmax-simply-isnt.html
on Windows and indeed other operating systems we already have the
correct code to get current working directory. so we just need to
update dmd to use this.
https://github.com/dlang/phobos/blob/v2.076.0/std/file.d#L2681
"
