Thanks Charles,
I'm using O2 dated November 21 and its RTL32.inc was last modified on October 15 so this must be one and the same file.
You won't believe it but the offending line was a simple debugging
print hex(c) cr statement in the following piece of code:
........
case 0x3B // ';' ==> bypass comments recursively altogether
c = inchar()
while ((c != 0xA) && (c != EOF)) ' '\n' or end-of-file
' skip comments
print hex(c) cr ' <== the offending statement
c = inchar()
wend
if (c == EOF) then return TOK_EOF
return token() ' call own self recursively
........
that is part of Scheme source code tokenizer which is self-recursive when eliminating LISP comments. I think this may be due to different heap or stack reserve/commit
settings layout (PE Explorer shows equal settings) in gxo2.exe/exe+Oxygen.dll/standalone exe, but I'm not competent enough to verify this supposition.
Anyway all is well that ends well.