Re: What the heck does this backtrace mean?

Asfand Yar Qazi writes: > Hi, > > I'm the emacs-lisp n00b who's audaciously decided to take over > maintenance of ruby-modes. > > I'm having a great deal of difficulty figuring out what the dickens > the backtrace means. I can't even see where it's telling me the line > number or method name it failed on. It doesn't tell you that. Lisp is s-expression-oriented, ie all it really knows about are balanced parentheses. Because of the pervasive use of macros (many standard control structures are implemented as macros), it is very difficult to keep track of the position in the original file. The Lisp byte-compiler doesn't even try. > While compiling ruby-electric-mode in file > /home/ayqazi/src/packages/xemacs/cvs/packages/xemacs-packages/ruby-modes/ruby-electric.el: > ** reference to free variable ruby-electric-mode-hook > ** reference to free variable ruby-electric-mode-on-hook > ** reference to free variable ruby-electric-mode-off-hook > While compiling toplevel forms: > !! End of file or stream ((#<buffer " *Compiler Input*">)) This means that the compiler expected more input. This almost always means unbalanced parentheses, more rarely a typo of the wrong kind of parenthesis. Finding the error generally requires the programmer to look at the code. Consider (when (emacs-version >= 21 5) (setq debug-on-error t) (defun newfunction () (message "that's not my job mon!")) Is the defun subject to the when, or not? How is the poor compiler supposed to guess? To diagnose, go to the beginning of the file, and type M-: (while t (set-mark) (forward-sexp 1)) RET When the error occurs you can then use C-x C-x to find the beginning of the unterminated sexp. At that point, enter that sexp, and you can start stepping forward with C-M-f (forward-sexp), and when you go farther than you expect, that's the sexp with a problem. Recurse until the problem is obvious. ;-) Another technique is to step through a function typing TAB. When a line unexpectedly reindents, you've found a place where the programmer and Emacs disagree about sexp structure.