Clojurians Log v2

i think it turned out that the classpath length i had was too long for clj to launch a jvm on windows in some cases. when the classpath got slightly shorter, clj would manage to launch a jvm, but then clj.native-image would try to launch native-image with the classpath along with other options, causing the total command line length to exceed windows' limit. i'm now checking lengths of classpaths for a variety of projects locally to see typical sizes.

for reference, the limitation on the length of the string for invoking the native-image command executed in cmd.exe (via a .bat file) as observed here is 7126 characters. one more character and i get the error:

The input line is too long.
The syntax of the command is incorrect.

The java invocation in clojure adds not only the .cp file but also the .lib file I think, and several of its own options.

Ah, just the name of the .lib file...

exec "$JAVA_CMD" "${jvm_cache_opts[@]}" "${jvm_opts[@]}" "-Dclojure.libfile=$libs_file" -classpath "$cp" clojure.main "${main_cache_opts[@]}" "$@"

That total command line can only be 8K but it's going to include the full path to the java.exe file, plus all of the above...

$JavaCmd @JvmCacheOpts @JvmOpts "-Dclojure.libfile=$LibsFile" -classpath $CP clojure.main @MainCacheOpts @ClojureArgs

if it's cheap to test the java version and that's >= 9, one could use the @-file technique and put the classpath in a file instead of on the command line

iirc though the last survey suggested that java 8 is still quite prevalent

https://clojure.atlassian.net/browse/TDEPS-120

the pathing.jar approach might work, but apparently there are all sorts of "fun" limitations for the manifest file

https://github.com/taylorwood/clj.native-image/issues/18#issuecomment-559240320

i've looked at the code by timgilbert in TDEPS-120 (and lein-classpath-jar). as near as i can tell, the value it uses for the Class-Path: field in the manifest is a space-separate string of classpath elements. i am slightly surprised there are no problems with this, as i have read that there are a variety of constraints regarding lengths and formatting of values in a manifest file: https://stackoverflow.com/questions/3057841/too-long-line-in-manifest-file-while-trying-to-create-jar/3057862

it would be great if the current code works well as it certainly seems simpler than having to jump through the extra hoops that people seem to have (cf. the stackoverflow link).

https://github.com/timgilbert/tools.deps.alpha/blob/ccc4c58e2aecfd94d9be761e3e3b11c9195e3c31/src/main/clojure/clojure/tools/deps/alpha/script/make_classpath.clj#L73_L79

perhaps the Attribute class' put method "does the right thing". that would be great.

i guess i can try generating a pathing jar with timgilbert's code and look at the content of the manifest file :)

(i guess it's more likely that it's a different method that "does the right thing")

What if the jar has a space in the path?

perhaps i can test to find out

ok, i haven't tested the space in path thing yet, but i have examined a created pathing-jar's manifest.mf: https://pastebin.com/GkppSCnw

file: uris are used, so may be spaces will end up as %20

line lengths do appear to be about 72 chars as the jar spec says

the leading space on the subsequent lines is for continuation afaict

i tried putting a space in an element of the classpath and generating the pathing jar. as expected, a %20 showed up in the Class-Path: field's value.

when the pathing jar code is run on a linux box with windows file paths, the resulting file: uris are a bit wonky, but when run on a windows box, they seem ok: https://pastebin.com/qUEW7xYL

here's the wonky stuff: https://pastebin.com/EZs47wNU

may be that's not too surprising