Some pcre improvements

configure.ac

@@ -56,20 +56,48 @@ dnl gnulib will handle getopt and error functions
 dnl Check pcre2 availability
 AC_MSG_CHECKING([whether PCRE2 support is requested])
 AC_ARG_WITH([pcre2],
-            [AS_HELP_STRING([--with-pcre2],
-                            [use pcre2 regex library @<:@default=check@:>@])],
+            [AS_HELP_STRING([--with-pcre2@<:@=PATH@:>@],
+                            [use pcre2 regex library, optionally from PATH @<:@default=check@:>@])],
             [], [with_pcre2=check])
 LIBPCRE2=
 AS_IF([test "x$with_pcre2" != xno],
       [
        AC_MSG_RESULT($with_pcre2)
+       dnl Handle custom path for PCRE2
+       AS_IF([test "x$with_pcre2" != xyes && test "x$with_pcre2" != xcheck],
+             [
+              dnl Custom path specified
+              PCRE2_CPPFLAGS="-I$with_pcre2/include"
+              PCRE2_LDFLAGS="-L$with_pcre2/lib"
+              save_CPPFLAGS="$CPPFLAGS"
+              save_LDFLAGS="$LDFLAGS"
+              CPPFLAGS="$CPPFLAGS $PCRE2_CPPFLAGS"
+              LDFLAGS="$LDFLAGS $PCRE2_LDFLAGS"
+             ])
        AC_CHECK_HEADERS([pcre2posix.h], [], [LIBPCRE2=_missing_header])
        AC_CHECK_LIB([pcre2-posix${LIBPCRE2}], [regexec],
-                    [],
-                    [if test "x$with_pcre2" != xcheck; then
-                     AC_MSG_FAILURE(
-                       [--with-pcre2 was given, but test for pcre2-posix failed])
-                     fi]
+                    [
+                     dnl Success - add the flags permanently if custom path was used
+                     AS_IF([test "x$with_pcre2" != xyes && test "x$with_pcre2" != xcheck],
+                           [
+                            CPPFLAGS="$save_CPPFLAGS $PCRE2_CPPFLAGS"
+                            LDFLAGS="$save_LDFLAGS $PCRE2_LDFLAGS"
+                           ])
+                     dnl Add the library to LIBS
+                     LIBS="$LIBS -lpcre2-posix${LIBPCRE2}"
+                    ],
+                    [
+                     dnl Failure - restore original flags if custom path was used
+                     AS_IF([test "x$with_pcre2" != xyes && test "x$with_pcre2" != xcheck],
+                           [
+                            CPPFLAGS="$save_CPPFLAGS"
+                            LDFLAGS="$save_LDFLAGS"
+                           ])
+                     if test "x$with_pcre2" != xcheck; then
+                      AC_MSG_FAILURE(
+                        [--with-pcre2 was given, but test for pcre2-posix failed])
+                      fi
+                    ]
                     )
       ],
       AC_MSG_RESULT(no)

doc/patchutils.xml

@@ -2266,7 +2266,10 @@ will pipe patch of file #2 to vim - -R
 	<para>The regular expression is treated as POSIX Basic Regular
 	  Expression syntax, unless the <option>-E</option> option is
 	  given in which case POSIX Extended Regular Expression syntax
-	  is used.</para>
+	  is used. When compiled with PCRE2 support, PCRE regular expressions
+	  are used instead of POSIX regular expressions, and the <option>-E</option>
+	  option has no effect since PCRE already supports extended regular
+	  expression features by default.</para>
 
 	<para>For example, to see the patches in
 	  <filename>my.patch</filename> which contain the regular
@@ -2497,7 +2500,9 @@ will pipe patch of file #2 to vim - -R
 	    <option>--extended-regexp</option></term>
 	    <listitem>
 	      <para>Use POSIX Extended Regular Expression
-	        syntax.</para>
+	        syntax. Note: when compiled with PCRE2 support, this option
+	        has no effect as PCRE regular expressions are used by default
+	        and already support extended regular expression features.</para>
 	    </listitem>
 	  </varlistentry>
 

lib/Makefile

@@ -966,7 +966,7 @@ LIBGNU_LIBDEPS =
 LIBGNU_LTLIBDEPS = 
 LIBINTL = 
 LIBOBJS = 
-LIBS = -lpcre2-posix 
+LIBS =  -lpcre2-posix
 LIMITS_H = limits.h
 LN_S = ln -s
 LOCALENAME_ENHANCE_LOCALE_FUNCS = 0

src/filterdiff.c

@@ -1257,7 +1257,11 @@ const char * syntax_str =
 "  -v, --verbose\n"
 "            verbose output -- use more than once for extra verbosity\n"
 "  -E, --extended-regexp (grepdiff)\n"
+#ifdef HAVE_PCRE2POSIX_H
+"            this option has no effect as PCRE regexes are used by default (grepdiff)\n"
+#else
 "            use extended regexps, like egrep (grepdiff)\n"
+#endif
 "  -E, --empty-files-as-absent (lsdiff)\n"
 "            treat empty files as absent (lsdiff)\n"
 "  -f FILE, --file=FILE (grepdiff)\n"

tests/grepdiff-pcre2-extended/run-test

@@ -0,0 +1,27 @@
+#!/bin/sh
+
+# Test for PCRE2 extended regexp functionality (GitHub issue #60)
+
+. ${top_srcdir-.}/tests/common.sh
+
+# Create a simple test diff with both patterns
+cat << EOF > diff
+--- file1
++++ file1
+@@ -1,2 +1,3 @@
+ context
+-old
++landblockelim
++blockall
+EOF
+
+# Test extended regexp pattern with -E flag
+${GREPDIFF} -E 'landblockelim|blockall' diff 2>errors >output || exit 1
+
+[ -s errors ] && exit 1
+
+# Verify both patterns are found
+if ! grep -q "file1" output; then
+    echo "ERROR: Extended regexp pattern failed to match"
+    exit 1
+fi