Disable the PCRE JIT compiler by default

The JIT compiler is broken on some versions of PCRE, at least on i386,
so disable it by default.  It can be enabled using --enable-pcre-jit
to configure.

Fixes #1191

configure.ac

@@ -531,6 +531,17 @@ fi
 
 AC_DEFINE_UNQUOTED([VCC_CC],"$VCC_CC",[C compiler command line for VCL code])
 
+# --enable-pcre-jit
+AC_ARG_ENABLE(pcre-jit,
+    AS_HELP_STRING([--enable-pcre-jit],
+	[use the PCRE JIT compiler (default is NO)]),
+    ,
+    [enable_pcre_jit=no])
+
+if test "$enable_pcre_jit" = yes; then
+   AC_DEFINE([USE_PCRE_JIT],[1],[use the PCRE JIT compiler])
+fi
+
 # Stupid automake needs this
 VTC_TESTS="$(cd $srcdir/bin/varnishtest && echo tests/*.vtc)"
 AC_SUBST(VTC_TESTS)

lib/libvarnish/vre.c

@@ -37,8 +37,10 @@
 
 #include "vre.h"
 
-#ifndef PCRE_STUDY_JIT_COMPILE
-#define PCRE_STUDY_JIT_COMPILE 0
+#if USE_PCRE_JIT
+#define VRE_STUDY_JIT_COMPILE PCRE_STUDY_JIT_COMPILE
+#else
+#define VRE_STUDY_JIT_COMPILE 0
 #endif
 
 #if PCRE_MAJOR < 8 || (PCRE_MAJOR == 8 && PCRE_MINOR < 20)
@@ -78,7 +80,7 @@ VRE_compile(const char *pattern, int options,
 		VRE_free(&v);
 		return (NULL);
 	}
-	v->re_extra = pcre_study(v->re, PCRE_STUDY_JIT_COMPILE, errptr);
+	v->re_extra = pcre_study(v->re, VRE_STUDY_JIT_COMPILE, errptr);
 	if (*errptr != NULL) {
 		VRE_free(&v);
 		return (NULL);