HCR depends on nimcachedir.len

[timotheecour]

[EDIT]
After a painful reduction, I found this bug while working on #13999

--hotCodeReloading "works" or fails depending on the length of nimcachedir (from --nimcache) /cc @zah

That's a serious bug because depending on unrelated changes you'll have something working or not, and it can be hard to debug.

Example

when true:
  import os
  echo commandLineParams()

• step 1: nim c lib/nimhcr.nim
• step 2:XDG_CONFIG_HOME= nim c --forceBuild --hotCodeReloading:on -o:/tmp/z13 --hints:off --passl:-Wl,-rpath,lib --skipusercfg --skipparentcfg --nimcache:/tmp/D20201205T1650_D20201205T184232_nimcache10x main.nim

where:

• XDG_CONFIG_HOME= and --skipusercfg --skipparentcfg are to ignore user's environment
• --passl:-Wl,-rpath,lib is to avoid runtime error could not load: libnimhcr.dylib

Current Output

/tmp/z13 a1 a2 
@[]

Expected Output

/tmp/z13 a1 a2
@["a1", "a2"]

Additional Information

D20201205T165017
1.5.1 devel edce589

• it works if not using --hotCodeReloading:on
• it works if using --nimcache:/tmp/D20201205T1650_nimcache10x, or so long the length of nimcachedir is <= some threshold, then fails after that threshold

[timotheecour]

pretty sure it's related to this:

      # nasty nasty hack to get the command line functionality working with HCR
      # register the 2 variables on behalf of the os module which might not even
      # be loaded (in which case it will get collected but that is not a problem)
      let osModulePath = ($systemModulePath).replace("stdlib_system", "stdlib_os").rope
      g.mainDatInit.addf("\thcrAddModule($1);\n", [osModulePath])
      g.mainDatInit.add("\tint* cmd_count;\n")
      g.mainDatInit.add("\tchar*** cmd_line;\n")
      g.mainDatInit.addf("\thcrRegisterGlobal($1, \"cmdCount\", sizeof(cmd_count), NULL, (void**)&cmd_count);$N", [osModulePath])
      g.mainDatInit.addf("\thcrRegisterGlobal($1, \"cmdLine\", sizeof(cmd_line), NULL, (void**)&cmd_line);$N", [osModulePath])
      g.mainDatInit.add("\t*cmd_count = cmdCount;\n")
      g.mainDatInit.add("\t*cmd_line = cmdLine;\n")

[timotheecour]

indeed..., I fixed it in timotheecour#424