bug#63225: Compiling regexp patterns (and REGEXP_CACHE_SIZE in search.c)

["Mattias Engdegård" <mattias.engdegard@gmail.com>]

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5 maj 2023 kl. 18.26 skrev Mattias Engdegård <mattias.engdegard@gmail.com>:

> Stupid printf-debugging actually, nothing fancier than that.

Here is some of that stupidity I promised. You probably want to use it with

  (set-regexp-trace-file "re.log")
  (unwind-protect
      (do-something-interesting)
    (set-regexp-trace-file nil))

so that you don't trace more than necessary. The file may become large, but it's useful data for off-line analysis, scripted or just looking at it in an editor.
The first letter of each line indicates a regexp cache hit (H) or miss (M).


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From cd66a560a74d2ed94202cab278455544f0c9337c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mattias=20Engdeg=C3=A5rd?= <mattiase@acm.org>
Date: Sun, 7 May 2023 14:05:31 +0200
Subject: [PATCH 3/3] Regexp tracing: add set-regexp-trace-file

---
 src/search.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

diff --git a/src/search.c b/src/search.c
index c454d5e1ca9..b378db152a2 100644
--- a/src/search.c
+++ b/src/search.c
@@ -34,6 +34,10 @@ Copyright (C) 1985-1987, 1993-1994, 1997-1999, 2001-2023 Free Software
 
 #include "regex-emacs.h"
 
+#include <stdio.h>
+
+static FILE *regexp_trace_file = NULL;
+
 #define DEFAULT_REGEXP_CACHE_SIZE 20
 
 /* If the regexp is non-nil, then the buffer contains the compiled form
@@ -200,6 +204,7 @@ compile_pattern (Lisp_Object pattern, struct re_registers *regp,
 {
   struct regexp_cache *cp, **cpp, **lru_nonbusy;
 
+  bool cache_hit = false;
   for (cpp = &searchbuf_head, lru_nonbusy = NULL; ; cpp = &cp->next)
     {
       cp = *cpp;
@@ -224,6 +229,7 @@ compile_pattern (Lisp_Object pattern, struct re_registers *regp,
 	  && cp->buf.charset_unibyte == charset_unibyte)
         {
           regexp_cache_hit++;
+	  cache_hit = true;
           break;
         }
 
@@ -243,6 +249,26 @@ compile_pattern (Lisp_Object pattern, struct re_registers *regp,
 	}
     }
 
+  if (regexp_trace_file) {
+    fprintf(regexp_trace_file, "%c \"", cache_hit ? 'H' : 'M');
+    ptrdiff_t n = SBYTES (pattern);
+    for (ptrdiff_t i = 0; i < n; i++) {
+      unsigned char c = SREF (pattern, i);
+      switch (c) {
+      case '"': case '\\': fprintf(regexp_trace_file, "\\%c", c); break;
+      case '\n': fprintf(regexp_trace_file, "\\n"); break;
+      case '\t': fprintf(regexp_trace_file, "\\t"); break;
+      default:
+	if (c < 32 || c == 127)
+	  fprintf(regexp_trace_file, "\\x%02x", c);
+	else
+	  putc(c, regexp_trace_file);
+	break;
+      }
+    }
+    fprintf(regexp_trace_file, "\"\n");
+  }
+
   /* When we get here, cp (aka *cpp) contains the compiled pattern,
      either because we found it in the cache or because we just compiled it.
      Move it to the front of the queue to mark it as most recently used.  */
@@ -3424,6 +3450,27 @@ DEFUN ("set-regexp-cache-size", Fset_regexp_cache_size, Sset_regexp_cache_size,
   return Qnil;
 }
 
+DEFUN ("set-regexp-trace-file", Fset_regexp_trace_file, Sset_regexp_trace_file,
+       1, 1, 0,
+       doc: /* Set the regexp trace file to FILE.  Internal use only.
+Use `nil' as argument to stop tracing.  */)
+  (Lisp_Object file)
+{
+  if (NILP (file)) {
+    fclose (regexp_trace_file);
+    regexp_trace_file = NULL;
+  } else {
+    CHECK_STRING (file);
+    if (regexp_trace_file)
+      Fset_regexp_trace_file (Qnil);
+    FILE *f = fopen (SSDATA (file), "a");
+    if (!f)
+      report_file_error ("opening regexp trace file", file);
+    regexp_trace_file = f;
+  }
+  return Qnil;
+}
+
 void
 mark_regexp_cache (void)
 {
@@ -3514,6 +3561,7 @@ syms_of_search (void)
   defsubr (&Snewline_cache_check);
   defsubr (&Sregexp_cache_size);
   defsubr (&Sset_regexp_cache_size);
+  defsubr (&Sset_regexp_trace_file);
 
   pdumper_do_now_and_after_load (syms_of_search_for_pdumper);
 }
-- 
2.32.0 (Apple Git-132)