[PATCH v2 1/2] Fix pager search behavior with REG_NEWLINE.

[Kevin J. McCarthy]

REG_NEWLINE causes ^ to match both BOS and after a newline, and $ to
match both EOS and just before a newline.

This leads to weird behavior with a pager search such as /^a*$/.  This
will end up matching every line:
  - ^ matches after the newline
  - a* matches nothing
  - $ matches EOS

Removing the newlines would be more painful, because the parser
requires them in several places, for things like header to body
switching, matching signatures, and breaking out of some loops.

Instead do the same thing that match_body_patterns() does: temporarily
remove the newlines during the regex search.

Then, remove the REG_NEWLINE flag from all the REGCOMP calls.

Thanks to Alejandro Colomar for his review and suggested cleanup.
---
 pager.c | 70 ++++++++++++++++++++++++++++++++++++---------------------
 1 file changed, 45 insertions(+), 25 deletions(-)

diff --git a/pager.c b/pager.c
index 92fa152a..201dad91 100644
--- a/pager.c
+++ b/pager.c
@@ -1268,6 +1268,48 @@ bail:
   return rc;
 }
 
+static void resolve_search(struct line_t *lineInfo, int n, char *fmt,
+                           regex_t *SearchRE)
+{
+  size_t fmtlen;
+  int has_nl = 0, offset = 0;
+  regmatch_t pmatch[1];
+
+  /* don't consider line endings part of the buffer
+   * for regex matching */
+  fmtlen = mutt_strlen(fmt);
+  if (fmtlen > 0 && fmt[fmtlen - 1] == '\n')
+  {
+    has_nl = 1;
+    fmt[fmtlen - 1] = 0;
+  }
+
+  offset = 0;
+  lineInfo[n].search_cnt = 0;
+  while (regexec(SearchRE, fmt + offset, 1, pmatch, (offset ? REG_NOTBOL : 0)) 
== 0)
+  {
+    if (++(lineInfo[n].search_cnt) > 1)
+      safe_realloc(&(lineInfo[n].search),
+                   (lineInfo[n].search_cnt) * sizeof(struct syntax_t));
+    else
+      lineInfo[n].search = safe_malloc(sizeof(struct syntax_t));
+    pmatch[0].rm_so += offset;
+    pmatch[0].rm_eo += offset;
+    (lineInfo[n].search)[lineInfo[n].search_cnt - 1].first = pmatch[0].rm_so;
+    (lineInfo[n].search)[lineInfo[n].search_cnt - 1].last = pmatch[0].rm_eo;
+
+    if (pmatch[0].rm_eo == pmatch[0].rm_so)
+      offset++; /* avoid degenerate cases */
+    else
+      offset = pmatch[0].rm_eo;
+    if (!fmt[offset])
+      break;
+  }
+
+  if (has_nl)
+    fmt[fmtlen - 1] = '\n';
+}
+
 static int format_line(struct line_t **lineInfo, int n, unsigned char *buf,
                        int flags, ansi_attr *pa, int cnt,
                        int *pspace, int *pvch, int *pcol, int *pspecial,
@@ -1483,12 +1525,10 @@ display_line(FILE *f, LOFF_T *last_pos, struct line_t 
**lineInfo, int n,
   int ch, vch, col, cnt, b_read;
   int buf_ready = 0, change_last = 0;
   int special;
-  int offset;
   COLOR_ATTR def_color;
   int m;
   int rc = -1;
   ansi_attr a = {0,-1,-1,-1};
-  regmatch_t pmatch[1];
 
   if (n == *last)
   {
@@ -1567,27 +1607,7 @@ display_line(FILE *f, LOFF_T *last_pos, struct line_t 
**lineInfo, int n,
       goto out;
     }
 
-    offset = 0;
-    (*lineInfo)[n].search_cnt = 0;
-    while (regexec(SearchRE, (char *) fmt + offset, 1, pmatch, (offset ? 
REG_NOTBOL : 0)) == 0)
-    {
-      if (++((*lineInfo)[n].search_cnt) > 1)
-        safe_realloc(&((*lineInfo)[n].search),
-                     ((*lineInfo)[n].search_cnt) * sizeof(struct syntax_t));
-      else
-        (*lineInfo)[n].search = safe_malloc(sizeof(struct syntax_t));
-      pmatch[0].rm_so += offset;
-      pmatch[0].rm_eo += offset;
-      ((*lineInfo)[n].search)[(*lineInfo)[n].search_cnt - 1].first = 
pmatch[0].rm_so;
-      ((*lineInfo)[n].search)[(*lineInfo)[n].search_cnt - 1].last = 
pmatch[0].rm_eo;
-
-      if (pmatch[0].rm_eo == pmatch[0].rm_so)
-        offset++; /* avoid degenerate cases */
-      else
-        offset = pmatch[0].rm_eo;
-      if (!fmt[offset])
-        break;
-    }
+    resolve_search(*lineInfo, n, (char *) fmt, SearchRE);
   }
 
   if (!(flags & MUTT_SHOW) && (*lineInfo)[n+1].offset > 0)
@@ -1859,7 +1879,7 @@ static void pager_menu_redraw(MUTTMENU *pager_menu)
       if ((rd->SearchCompiled = Resize->SearchCompiled))
       {
         if ((err = REGCOMP(&rd->SearchRE, rd->searchbuf,
-                           REG_NEWLINE | mutt_which_case(rd->searchbuf))) != 0)
+                           mutt_which_case(rd->searchbuf))) != 0)
         {
           regerror(err, &rd->SearchRE, buffer, sizeof(buffer));
           mutt_error("%s", buffer);
@@ -2454,7 +2474,7 @@ search_next:
           }
         }
 
-        if ((err = REGCOMP(&rd.SearchRE, searchbuf, REG_NEWLINE | 
mutt_which_case(searchbuf))) != 0)
+        if ((err = REGCOMP(&rd.SearchRE, searchbuf, 
mutt_which_case(searchbuf))) != 0)
         {
           regerror(err, &rd.SearchRE, buffer, sizeof(buffer));
           mutt_error("%s", buffer);
-- 
2.54.0