MDEV-4127 : Export additional symbols when building RPM,

to enable both recompiling mysqli or odbc from sources in addition to drop-in replacement functionality.

The case in question is compiling mysqli from sources, that needs client_errors via ER() macro.

Previously, we exported it as mysql_client_errors (compatibly to Fedora's style symbol renaming, see MDEV-3842).
However, if MariaDB header files are used when compiling mysqli, client_errors needs to be exported with its original name.

libmysql/CMakeLists.txt

@@ -243,15 +243,22 @@ IF(CMAKE_SYSTEM_NAME MATCHES "Linux")
   
   IF(RPM)
     # Fedora & Co declared following functions as part of API 
-    # These functions are alias of another function (given mysql_ prefix=. The 
-    # renaming is handled in rpm_support.cc below
     SET(CLIENT_API_EXTRA
       mysql_default_charset_info
       mysql_get_charset
       mysql_get_charset_by_csname
       mysql_net_realloc
       mysql_client_errors
-    )
+
+      #  Also export the non-renamed variants
+      # (in case someone wants to rebuild mysqli-php or something similar)
+      # See MDEV-4127
+      default_charset_info
+      get_charset
+      get_charset_by_csname
+      net_realloc
+      client_errors)  
+  
     # Add special script to fix symbols renames by Fedora
     SET(CLIENT_SOURCES_EXTRA ${CLIENT_SOURCES} rpm_support.cc)
     SET(VERSION_SCRIPT_TEMPLATE 

libmysql/libmysql_rpm_version.in

@@ -34,15 +34,27 @@ libmysqlclient_18 {
 	@CLIENT_API_5_5_LIST@
 #
 # Ideally the following symbols wouldn't be exported, but various applications
-# require them.  We limit the namespace damage by prefixing mysql_
+# require them.  Fedora limits the namespace damage by prefixing mysql_
 # (see mysql-dubious-exports.patch), which means the symbols are not present
 # in libmysqlclient_16.
 #
+# MariaDB does not do the Fedora-style function renaming via #define in headers, 
+# however it exports mysql_ prefixed symbols in addition to the "normal" ones.
+#
+# To ensure successful recompilation of affected projects, as well as drop-in replacement
+# for MySQL libraries, provided by distribution, both original symbols and their mysql_ 
+# prefixed counterparts have to be exported.
+
 # mysql-connector-odbc requires these
 	mysql_default_charset_info;
 	mysql_get_charset;
 	mysql_get_charset_by_csname;
 	mysql_net_realloc;
+	default_charset_info;
+	get_charset;
+	get_charset_by_csname;
+	net_realloc;
 # PHP's mysqli.so requires this (via the ER() macro)
 	mysql_client_errors;
+	client_errors;
 };