MXS-2785: Report PCRE2 errors

The substitution string could cause errors.

include/maxscale/pcre2.hh

@@ -28,10 +28,15 @@ namespace maxscale
  * @param re Compiled pattern to use
  * @param subject Subject string
  * @param replace Replacement string
+ * @param error   Pointer to std::string where any error messages are stored
  *
- * @return The replaced string or the original string if no replacement was made
+ * @return The replaced string or the original string if no replacement was made. Returns an empty string when
+ * any PCRE2 error is encountered.
  */
-std::string pcre2_substitute(pcre2_code* re, const std::string& subject, const std::string& replace);
+std::string pcre2_substitute(pcre2_code* re,
+                             const std::string& subject,
+                             const std::string& replace,
+                             std::string* error = nullptr);
 
 /**
  * @class CloserTraits<pcre2_code*> pcre2.hh <maxscale/pcre2.hh>

server/core/maxscale_pcre2.cc

@@ -248,8 +248,12 @@ bool mxs_pcre2_check_match_exclude(pcre2_code* re_match,
 
 namespace maxscale
 {
-std::string pcre2_substitute(pcre2_code* re, const std::string& subject, const std::string& replace)
+std::string pcre2_substitute(pcre2_code* re,
+                             const std::string& subject,
+                             const std::string& replace,
+                             std::string* error)
 {
+    mxb_assert(re);
     std::string rval = subject;
     size_t size_tmp = rval.size();
     int rc;
@@ -263,7 +267,21 @@ std::string pcre2_substitute(pcre2_code* re, const std::string& subject, const s
         size_tmp = rval.size();
     }
 
-    rval.resize(size_tmp);
+    if (rc < 0)
+    {
+        if (error)
+        {
+            char errbuf[1024];
+            pcre2_get_error_message(rc, (PCRE2_UCHAR*)errbuf, sizeof(errbuf));
+            *error = errbuf;
+        }
+
+        rval.clear();
+    }
+    else
+    {
+        rval.resize(size_tmp);
+    }
 
     return rval;
 }

server/modules/filter/binlogfilter/binlogfilter.hh

@@ -30,6 +30,7 @@ struct BinlogConfig
         , exclude(pParams->get_compiled_regex("exclude", 0, nullptr).release())
         , md_exclude(exclude ? pcre2_match_data_create_from_pattern(exclude, nullptr) : nullptr)
         , rewrite_src(pParams->get_compiled_regex(REWRITE_SRC, 0, nullptr).release())
+        , rewrite_src_pattern(pParams->get_string(REWRITE_SRC))
         , rewrite_dest(pParams->get_string(REWRITE_DEST))
     {
     }
@@ -39,6 +40,7 @@ struct BinlogConfig
     pcre2_code*       exclude;
     pcre2_match_data* md_exclude;
     pcre2_code*       rewrite_src;
+    std::string       rewrite_src_pattern;
     std::string       rewrite_dest;
 };
 

server/modules/filter/binlogfilter/binlogfiltersession.cc

@@ -851,10 +851,17 @@ void BinlogFilterSession::checkStatement(GWBUF** buffer, const REP_HEADER& hdr)
 
     if (!m_skip && config.rewrite_src)
     {
-        auto new_db = mxs::pcre2_substitute(config.rewrite_src, db, config.rewrite_dest);
+        std::string err;
-        auto new_sql = mxs::pcre2_substitute(config.rewrite_src, sql, config.rewrite_dest);
+        auto new_db = mxs::pcre2_substitute(config.rewrite_src, db, config.rewrite_dest, &err);
+        auto new_sql = mxs::pcre2_substitute(config.rewrite_src, sql, config.rewrite_dest, &err);
 
-        if (db != new_db || sql != new_sql)
+        if (new_db.empty() || new_sql.empty())
+        {
+            MXS_ERROR("PCRE2 error on pattern '%s' with replacement '%s': %s",
+                      config.rewrite_src_pattern.c_str(),
+                      config.rewrite_dest.c_str(), err.c_str());
+        }
+        else if (db != new_db || sql != new_sql)
         {
             db = new_db;
             sql = new_sql;