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digitalmars.D.learn - dub and -lowmem: does nothing

reply Anonymouse <zorael gmail.com> writes:
Manjaro/Arch x86_64, dmd v2.091.0, dub 1.19.0.

I have a project which dmd on Windows fails to compile, throwing 
an OutOfMemoryError[1]. Up until recently it could be worked 
around by using `--build-mode=singleFile`, but now that's no 
longer enough and errors out too (on AppVeyor).

The obvious solution is to set `-lowmem` in dub.sdl, but it seems 
to do nothing, as measured *in Linux* by the amount of memory 
used with zsh's `time` shell built-in.

If using zsh time, you may need the following environmental 
variable to get the required output:

```
TIMEFMT='%J   %U  user %S system %P cpu %*E total
avg shared (code):         %X KB
avg unshared (data/stack): %D KB
total (sum):               %K KB
max memory:                %M MB
page faults from disk:     %F
other page faults:         %R'
```

A gutted test branch: (has two dependencies)

 git clone https://github.com/zorael/tests.git -b lowmem


1. `dub build` on a default configuration without -lowmem defined 
shows some ~2011 Mb used.
2. If I run dub with -v, then copy the dmd command it runs and 
execute it manually, I get the same ~2012 Mb used. Close enough, 
makes sense.
3. `dub build -c lowmem` for an identical configuration but with 
dflags "-lowmem" added, nothing changes and I still get ~2011 Mb 
used.
4. If I run dub with -v on the lowmem configuration and 
copy/paste *the same command it ran*, unmodified, I suddenly get 
the more expected ~1183 Mb used.

Log: https://pastebin.com/raw/yDnCj1KJ

-lowmem is visibly present in the dmd command listed with -v, but 
it seems to do nothing through dub.

How? Why?



 dub remove lu --version="*"
 dub remove dialect --version="*"


[1]: https://issues.dlang.org/show_bug.cgi?id=20562
Mar 20 2020
parent reply kinke <noone nowhere.com> writes:
On Friday, 20 March 2020 at 23:37:52 UTC, Anonymouse wrote:

 4. If I run dub with -v on the lowmem configuration and 
 copy/paste *the same command it ran*, unmodified, I suddenly 
 get the more expected ~1183 Mb used.

 [...]

 -lowmem is visibly present in the dmd command listed with -v, 
 but it seems to do nothing through dub.

 How? Why?


Most likely because dub doesn't actually invoke the listed 
command, but uses a response file to work around cmdline length 
limits. -lowmem in response files is ignored by DMD (needs to be 
parsed and set before druntime initialization, but response file 
parsing needs druntime + GC). It works for LDC though.
Mar 20 2020
parent reply Anonymouse <zorael gmail.com> writes:
On Saturday, 21 March 2020 at 00:17:37 UTC, kinke wrote:

 Most likely because dub doesn't actually invoke the listed 
 command, but uses a response file to work around cmdline length 
 limits. -lowmem in response files is ignored by DMD (needs to 
 be parsed and set before druntime initialization, but response 
 file parsing needs druntime + GC). It works for LDC though.


So there is no way to do -lowmem with dub and dmd?

I'm not having out-of-memory problems with ldc, luckily.
Mar 21 2020
parent Steven Schveighoffer <schveiguy gmail.com> writes:
On 3/21/20 5:34 AM, Anonymouse wrote:

 On Saturday, 21 March 2020 at 00:17:37 UTC, kinke wrote:

 Most likely because dub doesn't actually invoke the listed command, 
 but uses a response file to work around cmdline length limits. -lowmem 
 in response files is ignored by DMD (needs to be parsed and set before 
 druntime initialization, but response file parsing needs druntime + 
 GC). It works for LDC though.


 
 So there is no way to do -lowmem with dub and dmd?
 
 I'm not having out-of-memory problems with ldc, luckily.


I found the same thing. dub says it's passing -lowmem (and at the same 
time I wanted it to print GC profile data). Does not work.

I've done exactly what you did, use -v and then copy-paste the final 
command line.

Very annoying. If there's not a bug on this yet, I'd say there needs to 
be (on DMD I would say).

-Steve
Mar 21 2020