X-Git-Url: http://repo.macrolet.net/gitweb/?a=blobdiff_plain;f=src%2Fcode%2Fearly-extensions.lisp;h=74f0b8fdaf851cd6512709eeb67b752d7d821102;hb=ef0891e470ff35840def7a5717ede18a58266e76;hp=8b657cc12e2a05794a44c99b03e17d74e2d0d002;hpb=2df8da85688355b4f4f31314246483ccea364746;p=sbcl.git

diff --git a/src/code/early-extensions.lisp b/src/code/early-extensions.lisp
index 8b657cc..74f0b8f 100644
--- a/src/code/early-extensions.lisp
+++ b/src/code/early-extensions.lisp
@@ -1381,3 +1381,44 @@ to :INTERPRET, an interpreter will be used.")
          (defun ,name (,@head &more ,more-context ,more-count)
            ,@body))
        (setf (%simple-fun-arglist #',name) ',lambda-list))))
+
+;;; Signalling an error when trying to print an error condition is
+;;; generally a PITA, so whatever the failure encountered when
+;;; wondering about FILE-POSITION within a condition printer, 'tis
+;;; better silently to give up than to try to complain.
+(defun file-position-or-nil-for-error (stream &optional (pos nil posp))
+  ;; Arguably FILE-POSITION shouldn't be signalling errors at all; but
+  ;; "NIL if this cannot be determined" in the ANSI spec doesn't seem
+  ;; absolutely unambiguously to prohibit errors when, e.g., STREAM
+  ;; has been closed so that FILE-POSITION is a nonsense question. So
+  ;; my (WHN) impression is that the conservative approach is to
+  ;; IGNORE-ERRORS. (I encountered this failure from within a homebrew
+  ;; defsystemish operation where the ERROR-STREAM had been CL:CLOSEd,
+  ;; I think by nonlocally exiting through a WITH-OPEN-FILE, by the
+  ;; time an error was reported.)
+  (if posp
+      (ignore-errors (file-position stream pos))
+      (ignore-errors (file-position stream))))
+
+(defun stream-error-position-info (stream &optional position)
+  (unless (interactive-stream-p stream)
+    (let ((now (file-position-or-nil-for-error stream))
+          (pos position))
+      (when (and (not pos) now (plusp now))
+        ;; FILE-POSITION is the next character -- error is at the previous one.
+        (setf pos (1- now)))
+      (let (lineno colno)
+        (when (and pos
+                   (< pos sb!xc:array-dimension-limit)
+                   (file-position stream :start))
+          (let ((string
+                  (make-string pos :element-type (stream-element-type stream))))
+            (when (= pos (read-sequence string stream))
+              ;; Lines count from 1, columns from 0. It's stupid and traditional.
+              (setq lineno (1+ (count #\Newline string))
+                    colno (- pos (or (position #\Newline string :from-end t) 0)))))
+          (file-position-or-nil-for-error stream now))
+        (remove-if-not #'second
+                       (list (list :line lineno)
+                             (list :column colno)
+                             (list :file-position pos)))))))