From 55fd5122486e130e33f58c6b9288c0211db5a076 Mon Sep 17 00:00:00 2001
From: Kevin McCarthy <kevin@8t8.us>
Date: Sun, 25 Nov 2018 19:48:49 -0800
Subject: [PATCH] Prevent trying to match a failing color body regex
 repeatedly.

Emails with really long lines (e.g. spam), can suffer performance if a
complicated regex is matched to no effect over and over.  If the regex
failed at the beginning, it won't match at the end of another's regex
match range, so turn it off.
---
 mutt_curses.h |  4 ++++
 pager.c       | 25 +++++++++++++++++++------
 2 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/mutt_curses.h b/mutt_curses.h
index d12b5790..bd563f7b 100644
--- a/mutt_curses.h
+++ b/mutt_curses.h
@@ -153,6 +153,10 @@ typedef struct color_line
   short bg;
   int pair;
   struct color_line *next;
+
+  unsigned int stop_matching : 1; /* used by the pager for body patterns,
+                                     to prevent the color from being retried
+                                     once it fails. */
 } COLOR_LINE;
 
 #define MUTT_PROGRESS_SIZE      (1<<0)  /* traffic-based progress */
diff --git a/pager.c b/pager.c
index 930c1916..5fb8629d 100644
--- a/pager.c
+++ b/pager.c
@@ -751,7 +751,7 @@ resolve_types (char *buf, char *raw, struct line_t *lineInfo, int n, int last,
 		struct q_class_t **QuoteList, int *q_level, int *force_redraw,
 		int q_classify)
 {
-  COLOR_LINE *color_line;
+  COLOR_LINE *color_line, *color_list;
   regmatch_t pmatch[1];
   int found, offset, null_rx, i;
 
@@ -872,6 +872,16 @@ resolve_types (char *buf, char *raw, struct line_t *lineInfo, int n, int last,
     i = 0;
     offset = 0;
     lineInfo[n].chunks = 0;
+    if (lineInfo[n].type == MT_COLOR_HDEFAULT)
+      color_list = ColorHdrList;
+    else
+      color_list = ColorBodyList;
+    color_line = color_list;
+    while (color_line)
+    {
+      color_line->stop_matching = 0;
+      color_line = color_line->next;
+    }
     do
     {
       if (!buf[offset])
@@ -879,13 +889,11 @@ resolve_types (char *buf, char *raw, struct line_t *lineInfo, int n, int last,
 
       found = 0;
       null_rx = 0;
-      if (lineInfo[n].type == MT_COLOR_HDEFAULT)
-        color_line = ColorHdrList;
-      else
-        color_line = ColorBodyList;
+      color_line = color_list;
       while (color_line)
       {
-	if (regexec (&color_line->rx, buf + offset, 1, pmatch,
+	if (!color_line->stop_matching &&
+            regexec (&color_line->rx, buf + offset, 1, pmatch,
 		     (offset ? REG_NOTBOL : 0)) == 0)
 	{
 	  if (pmatch[0].rm_eo != pmatch[0].rm_so)
@@ -921,6 +929,11 @@ resolve_types (char *buf, char *raw, struct line_t *lineInfo, int n, int last,
 	  else
 	    null_rx = 1; /* empty regexp; don't add it, but keep looking */
 	}
+        /* Once a regexp fails to match, don't try matching it again.
+         * On very long lines this can cause a performance issue if there
+         * are other regexps that have many matches. */
+        else
+          color_line->stop_matching = 1;
 	color_line = color_line->next;
       }
 
-- 
2.40.0