grep: --version: print pcre version info

PCRE is integral to the functioning of grep's -P option, so it is in our
interest to make it easy to see which version of PCRE grep uses.
* src/grep.c [HAVE_LIBPCRE]: Include <pcre2.h>.
[HAVE_LIBPCRE] (main): Print pcre version info.
* tests/version-pcre: New test for this.
* tests/Makefile.am (TESTS): Add the file name.
* NEWS (Changes in behavior): Mention it.

4 files changed, 36 insertions, 0 deletions

diff --git a/NEWS b/NEWS
index 060e9386..029aaf1c 100644
--- a/NEWS
+++ b/NEWS
@@ -14,6 +14,14 @@ GNU grep NEWS                                    -*- outline -*-
   when running on 32-bit x86 and ARM hosts using glibc 2.34+.
   [bug introduced in grep 3.9]
 
+** Changes in behavior
+
+  grep --version now prints a line describing the version of PCRE2 it uses.
+  For example, it prints this when built with the very latest from git:
+    Built with PCRE 10.43-DEV 2023-01-15
+  or this with what's currently available in Fedora 37:
+    Built with PCRE 10.40 2022-04-14
+
 
 * Noteworthy changes in release 3.10 (2023-03-22) [stable]
 
diff --git a/src/grep.c b/src/grep.c
index 7547b641..bd776e8b 100644
--- a/src/grep.c
+++ b/src/grep.c
@@ -29,6 +29,11 @@
 #include <stdio.h>
 #include "system.h"
 
+#if HAVE_LIBPCRE
+# define PCRE2_CODE_UNIT_WIDTH 8
+# include <pcre2.h>
+#endif
+
 #include "argmatch.h"
 #include "c-ctype.h"
 #include "c-stack.h"
@@ -2830,6 +2835,12 @@ main (int argc, char **argv)
                    (char *) NULL);
       puts (_("Written by Mike Haertel and others; see\n"
               "<https://git.savannah.gnu.org/cgit/grep.git/tree/AUTHORS>."));
+#if HAVE_LIBPCRE
+      unsigned char buf[128];
+      (void) pcre2_config (PCRE2_CONFIG_VERSION, buf);
+      fputs (_("\nBuilt with PCRE "), stdout);
+      puts ((char *) buf);
+#endif
       return EXIT_SUCCESS;
     }
 
diff --git a/tests/Makefile.am b/tests/Makefile.am
index c9376b19..0ef96d44 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -178,6 +178,7 @@ TESTS =						\
   unibyte-bracket-expr				\
   unibyte-negated-circumflex			\
   utf8-bracket					\
+  version-pcre					\
   warn-char-classes				\
   word-delim-multibyte				\
   word-multi-file				\
@@ -254,6 +255,7 @@ TESTS_ENVIRONMENT =				\
   srcdir='$(srcdir)'				\
   top_srcdir='$(top_srcdir)'			\
   CC='$(CC)'					\
+  CONFIG_HEADER='$(abs_top_builddir)/$(CONFIG_INCLUDE)' \
   GREP_TEST_NAME=`echo $$tst|sed 's,^\./,,;s,/,-,g'` \
   MAKE=$(MAKE)					\
   MALLOC_PERTURB_=$(MALLOC_PERTURB_)		\
diff --git a/tests/version-pcre b/tests/version-pcre
new file mode 100755
index 00000000..d18daa69
--- /dev/null
+++ b/tests/version-pcre
@@ -0,0 +1,15 @@
+#! /bin/sh
+# Test for presence of pcre version number in --version output.
+#
+# Copyright (C) 2023 Free Software Foundation, Inc.
+#
+# Copying and distribution of this file, with or without modification,
+# are permitted in any medium without royalty provided the copyright
+# notice and this notice are preserved.
+
+. "${srcdir=.}/init.sh"; path_prepend_ ../src
+
+grep -q '^#define HAVE_LIBPCRE 1' "$CONFIG_HEADER" \
+  || skip_ 'built without PCRE support'
+
+grep --version | grep -qP '^Built with PCRE [\d.]+'