Prepend regerror() messages with "regexp error: "

The exact error messages returned by regerror() aren't standardized;
relying on them isn't portable. Thus, add a a prefix to make clear that
the subsequent message is a regexp parsing error, and only look for this
prefix in the test suite, ignoring the rest of the message.

1 files changed, 2 insertions, 2 deletions

diff --git a/lib/regexp-fields.cc b/lib/regexp-fields.cc
index 084bc8c0..f50da9a3 100644
--- a/lib/regexp-fields.cc
+++ b/lib/regexp-fields.cc
@@ -35,9 +35,9 @@ compile_regex (regex_t &regexp, const char *str)
     if (err != 0) {
 	size_t len = regerror (err, &regexp, NULL, 0);
 	char *buffer = new char[len];
-	std::string msg;
+	std::string msg = "Regexp error: ";
 	(void) regerror (err, &regexp, buffer, len);
-	msg.assign (buffer, len);
+	msg.append (buffer, len);
 	delete[] buffer;
 
 	throw Xapian::QueryParserError (msg);