etags: fix #line parsing (\\", long lines)

* lib-src/etags.c (readline): Don’t mishandle lines like
‘#line 1 "a//"’, which has an escaped backslash before ‘"’.
Don’t mishandle lines so long that sscanf overflows %n.

1 files changed, 11 insertions, 11 deletions

diff --git a/lib-src/etags.c b/lib-src/etags.c
index c316b3c7649..57ffbce380c 100644
--- a/lib-src/etags.c
+++ b/lib-src/etags.c
@@ -7375,26 +7375,26 @@ readline (linebuffer *lbp, FILE *stream)
       /* Check whether this is a #line directive. */
       if (result > 12 && strneq (lbp->buffer, "#line ", 6))
         {
-          intmax_t lno;
-          int start = 0;
+          char *lno_start = lbp->buffer + 6;
+          char *lno_end;
+          intmax_t lno = strtoimax (lno_start, &lno_end, 10);
+          char *quoted_filename
+            = lno_start < lno_end ? skip_spaces (lno_end) : NULL;
 
-          if (sscanf (lbp->buffer, "#line %"SCNdMAX" \"%n", &lno, &start) >= 1
-              && start > 0)     /* double quote character found */
+          if (quoted_filename && *quoted_filename == '"')
             {
-              char *endp = lbp->buffer + start;
+              char *endp = quoted_filename;
+              while (*++endp && *endp != '"')
+                endp += *endp == '\\' && endp[1];
 
-              while ((endp = strchr (endp, '"')) != NULL
-                     && endp[-1] == '\\')
-                endp++;
-              if (endp != NULL)
+              if (*endp)
                 /* Ok, this is a real #line directive.  Let's deal with it. */
                 {
                   char *taggedabsname;  /* absolute name of original file */
                   char *taggedfname;    /* name of original file as given */
-                  char *name;           /* temp var */
+                  char *name = quoted_filename + 1;
 
                   discard_until_line_directive = false; /* found it */
-                  name = lbp->buffer + start;
                   *endp = '\0';
                   canonicalize_filename (name);
                   taggedabsname = absolute_filename (name, tagfiledir);