carets: properly display when no line feed is present

[bison.git] / src / location.c

diff --git a/src/location.c b/src/location.c
index a749415878e2c1f0708beb54f0a814d5d18c18ba..66b9ffa6679f939968fae2107cba3fc00e5e2b7b 100644 (file)
--- a/src/location.c
+++ b/src/location.c
@@ -107,7 +107,7 @@ location_print (FILE *out, location loc)
                   quotearg_n_style (3, escape_quoting_style, loc.start.file));
   if (0 <= loc.start.line)
     {
-      res += fprintf(out, ":%d", loc.start.line);
+      res += fprintf (out, ":%d", loc.start.line);
       if (0 <= loc.start.column)
         res += fprintf (out, ".%d", loc.start.column);
     }
@@ -118,7 +118,7 @@ location_print (FILE *out, location loc)
                                         loc.end.file));
       if (0 <= loc.end.line)
         {
-          res += fprintf(out, ":%d", loc.end.line);
+          res += fprintf (out, ":%d", loc.end.line);
           if (0 <= end_col)
             res += fprintf (out, ".%d", end_col);
         }
@@ -138,6 +138,85 @@ location_print (FILE *out, location loc)
   return res;
 }
 
+
+/* Persistant data used by location_caret to avoid reopening and rereading the
+   same file all over for each error.  */
+struct caret_info
+{
+  FILE *source;
+  size_t line;
+  size_t offset;
+};
+
+static struct caret_info caret_info = { NULL, 1, 0 };
+
+void
+cleanup_caret ()
+{
+  if (caret_info.source)
+    fclose (caret_info.source);
+  caret_info.source = NULL;
+  caret_info.line = 1;
+  caret_info.offset = 0;
+}
+
+void
+location_caret (FILE *out, location loc)
+{
+  /* FIXME: find a way to support multifile locations, and only open once each
+     file. That would make the procedure future-proof.  */
+  if (! (caret_info.source
+         || (caret_info.source = fopen (loc.start.file, "r")))
+      || loc.start.column == -1 || loc.start.line == -1)
+    return;
+
+  /* If the line we want to quote is seekable (the same line as the previous
+     location), just seek it. If it was a previous line, we lost track of it,
+     so return to the start of file.  */
+  if (caret_info.line <= loc.start.line)
+    fseek (caret_info.source, caret_info.offset, SEEK_SET);
+  else
+    {
+      caret_info.line = 1;
+      caret_info.offset = 0;
+      fseek (caret_info.source, caret_info.offset, SEEK_SET);
+    }
+
+  /* Advance to the line's position, keeping track of the offset.  */
+  while (caret_info.line < loc.start.line)
+    caret_info.line += getc (caret_info.source) == '\n';
+  caret_info.offset = ftell (caret_info.source);
+
+  /* Read the actual line.  Don't update the offset, so that we keep a pointer
+     to the start of the line.  */
+  {
+    char c = getc (caret_info.source);
+    if (c != EOF)
+      {
+        /* Quote the file, indent by a single column.  */
+        putc (' ', out);
+        do
+          putc (c, out);
+        while ((c = getc (caret_info.source)) != EOF && c != '\n');
+        putc ('\n', out);
+
+        {
+          /* The caret of a multiline location ends with the first line.  */
+          size_t len = loc.start.line != loc.end.line
+            ? ftell (caret_info.source) - caret_info.offset
+            : loc.end.column;
+          int i;
+
+          /* Print the carets (at least one), with the same indent as above.*/
+          fprintf (out, " %*s", loc.start.column - 1, "");
+          for (i = loc.start.column; i == loc.start.column || i < len; ++i)
+            putc ('^', out);
+          }
+        putc ('\n', out);
+      }
+  }
+}
+
 void
 boundary_set_from_string (boundary *bound, char *loc_str)
 {