Bug#397262: grep: Patch to dlopen PCRE so we can have -P

[Reuben Thomas]

Package: grep
Version: 2.5.1.ds2-5
Severity: wishlist
Tags: patch

As we discussed a while ago, I've made a patch for grep to use PCRE
via dlopen.

I'm afraid that I could not adequately beat the horrors of autotools
into submission, so my patch doesn't deal with linking or configuring.
I also don't understand Debian source packages that when they are
unpacked consist of a debian directory and a tarball, so my patch is
against the 2.5.1a sources. Sorry about this.

My patch is just for search.c. In order to build grep correctly, you
must configure so that PCRE is selected, but change -lpcre into -ldl.
I'm not sure how best to do that. Doing it hackily (i.e. patching
configure directly) would be easy (for someone who understands how the
Debian packages are built).

I hope this will sort out all the other bugs about -P!
-- System Information:
Debian Release: testing/unstable
  APT prefers testing
  APT policy: (500, 'testing')
Architecture: i386 (i686)
Shell:  /bin/sh linked to /bin/bash
Kernel: Linux 2.6.17-2-686
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8)

Versions of packages grep depends on:
ii  libc6                        2.3.6.ds1-7 GNU C Library: Shared libraries

grep recommends no packages.

-- no debconf information

--- grep-2.5.1a/src/search.c	2001-04-19 04:42:14.000000000 +0100
+++ grep-2.5.1a-dlopen-pcre/src/search.c	2006-11-06 00:58:36.000000000 +0000
@@ -37,6 +37,7 @@
 #include "error.h"
 #include "xalloc.h"
 #ifdef HAVE_LIBPCRE
+# include <dlfcn.h>
 # include <pcre.h>
 #endif
 
@@ -83,6 +84,35 @@
 static void Pcompile PARAMS ((char const *, size_t ));
 static size_t Pexecute PARAMS ((char const *, size_t, size_t *, int));
 
+
+static pcre *(*dl_pcre_compile)(const char *pattern, int options, const char **errptr, int *erroffset, const unsigned char *tableptr); 
+static pcre_extra *(*dl_pcre_study)(const pcre *code, int options, const char **errptr);
+static int (*dl_pcre_exec)(const pcre *code, const pcre_extra *extra, const char *subject, int length, int startoffset, int options, int *ovector, int ovecsize);
+static const unsigned char *(*dl_pcre_maketables)(void);
+
+static int map_pcre(void)
+{
+  static int library_mapped = 0;
+  void *library;
+
+  if (library_mapped) return 0;
+
+  library = dlopen("libpcre.so",RTLD_NOW);
+
+  if (!(dl_pcre_compile = dlsym(library,"pcre_compile"))) 
+    return -1;
+  if (!(dl_pcre_study = dlsym(library,"pcre_study"))) 
+    return -1;
+  if (!(dl_pcre_exec = dlsym(library,"pcre_exec"))) 
+    return -1;
+  if (!(dl_pcre_maketables = dlsym(library,"pcre_maketables"))) 
+    return -1;
+
+  library_mapped++;
+  return 0;
+}
+
+
 void
 dfaerror (char const *mesg)
 {
@@ -614,6 +644,11 @@
   char const *p;
   char const *pnul;
 
+  if (map_pcre()) {
+    error (2, 0, _("The -P option is not supported"));
+  }
+
+
   /* FIXME: Remove this restriction.  */
   if (eolbyte != '\n')
     error (2, 0, _("The -P and -z options cannot be combined"));
@@ -652,11 +687,11 @@
   if (match_lines)
     strcpy (n, ")$");
 
-  cre = pcre_compile (re, flags, &ep, &e, pcre_maketables ());
+  cre = dl_pcre_compile (re, flags, &ep, &e, dl_pcre_maketables ());
   if (!cre)
     error (2, 0, ep);
 
-  extra = pcre_study (cre, 0, &ep);
+  extra = dl_pcre_study (cre, 0, &ep);
   if (ep)
     error (2, 0, ep);
 
@@ -675,7 +710,14 @@
      is just for performance improvement in pcre_exec.  */
   int sub[300];
 
-  int e = pcre_exec (cre, extra, buf, size, 0, 0,
+  int e;
+
+  if (map_pcre()) {
+	abort();
+	return -1;
+  }
+
+  e = dl_pcre_exec (cre, extra, buf, size, 0, 0,
 		     sub, sizeof sub / sizeof *sub);
 
   if (e <= 0)