Fix mxb_strerror

The function should not be an inline function with a static variable. This
appears to cause problems on at least Debian Wheezy and is likely to cause
odd behavior on other platforms.

Also renamed the file to <maxbase/string.h> to better mirror how the
<string.h> file behaves.

maxutils/maxbase/include/maxbase/string.h

@@ -0,0 +1,20 @@
+#pragma once
+/*
+ * Copyright (c) 2016 MariaDB Corporation Ab
+ *
+ * Use of this software is governed by the Business Source License included
+ * in the LICENSE.TXT file and at www.mariadb.com/bsl11.
+ *
+ * Change Date: 2022-01-01
+ *
+ * On the date above, in accordance with the Business Source License, use
+ * of this software will be governed by version 2 or later of the General
+ * Public License.
+ */
+
+#include <maxbase/cdefs.h>
+
+/**
+ * Thread-safe strerror
+ */
+const char* mxb_strerror(int error);

maxutils/maxbase/src/CMakeLists.txt

@@ -3,6 +3,7 @@ add_library(maxbase STATIC
   eventcount.cc
   logger.cc
   stopwatch.cc
+  string.cc
   stacktrace.cc
   )
 set_target_properties(maxbase PROPERTIES VERSION "1.0.0" LINK_FLAGS -Wl,-z,defs)

maxutils/maxbase/src/logger.cc

@@ -22,7 +22,7 @@
 #include <cstdio>
 #include <ctime>
 
-#include <maxbase/error.h>
+#include <maxbase/string.h>
 
 // TODO: move <maxscale/debug.h> into maxbase
 #define ss_dassert(a)

maxutils/maxbase/src/string.cc

@@ -1,4 +1,3 @@
-#pragma once
 /*
  * Copyright (c) 2016 MariaDB Corporation Ab
  *
@@ -12,14 +11,19 @@
  * Public License.
  */
 
-#include <maxbase/cdefs.h>
+#include <maxbase/string.h>
 
 #include <string.h>
 
-inline const char* mxb_strerror(int error)
+namespace
+{
+
+thread_local char errbuf[512]; // Enough for all errors
+
+}
+
+const char* mxb_strerror(int error)
 {
-    // Enough for all errors
-    static thread_local char errbuf[512];
 #ifdef HAVE_GLIBC
     return strerror_r(error, errbuf, sizeof(errbuf));
 #else

server/core/log_manager.cc

@@ -22,7 +22,7 @@
 #include <mutex>
 
 #include <maxbase/atomic.h>
-#include <maxbase/error.h>
+#include <maxbase/string.h>
 #include <maxbase/logger.hh>
 
 #include <maxscale/alloc.h>