MySQL can't import a custom library for udf

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                          I am working on Linux Mint 17 Qiana with MySQL Ver 14.14 Distrib 5.5.53, for debian-linux-gnu (x86_64).

Following the instructions found here:

http://dev.mysql.com/doc/refman/5.7/en/adding-udf.html 

and subsequent pages, I have created a library file for my own user-defined function. But MySQL gives an error when I create the MySQL function from the library file.

Here are the steps I made.

I have created the following C file:
    
    #include 
    #include 
    #include 
    #include 
    
    #include 
    
    //*** Functions for compressing a protein sequence into a binary
    my_bool compress_protein_sequence_init(UDF_INIT* initid, UDF_ARGS* args, char* message) {
    	if(args->arg_count != 1) {
    		strcpy(message, "Error: compress_protein_sequence needs a string");
    		return 1;
    	}
    
    	if( args->arg_type != STRING_RESULT ) {
    		args->arg_type = STRING_RESULT;
    	}
    
    	return 0;
    }
    
    char* compress_protein_sequence(UDF_INIT* initid, UDF_ARGS* args, char* result, unsigned long* ret_length, char* is_null, char* error) {
    	unsigned long length = args->lengths;
    
    //*** Checking on the arguments
    
    	*ret_length = (unsigned long) length;
    
    	if(!(result = malloc(sizeof(char) * ((*ret_length) + 1)))) {
    		*is_null = 1;
    		*error=1;
    		*ret_length = 0;
    		return 0;
    	}
    	if(initid->ptr) {
    		free(initid->ptr);
    	}
    	initid->ptr = result;
    
    	memset( result, '\0', *ret_length + 1 );
    
    //*** Some logic
    
    	result[*ret_length] = '\0';
    	return result;
    }
    
    void compress_protein_sequence_deinit(UDF_INIT* initid) {
    	if( initid->ptr )
    		free( initid->ptr );
    }

I compile the C code:

    gcc -Wall -I/usr/local/include -shared -o libcompress_sequence.so -c compress_sequence.c

MySQL plugin directory is given by:

    SHOW VARIABLES LIKE '%plugin%';

the answer is:

    +---------------+------------------------+
    | Variable_name | Value                  |
    +---------------+------------------------+
    | plugin_dir    | /usr/lib/mysql/plugin/ |
    +---------------+------------------------+

So I put the libcompress_sequence.so in the plugin folder of MySQL:

    sudo cp libcompress_sequence.so /usr/lib/mysql/plugin/

I start MySQL in command line as root:

    mysql -u root -p

I chose a database then I execute this MySQL command:

    CREATE FUNCTION COMPRESS_PROTEIN_SEQUENCE RETURNS STRING SONAME 'libcompress_sequence.so';

and MySQL shows this error:

    ERROR 1126 (HY000): Can't open shared library 'libcompress_sequence.so' (errno: 0 /usr/lib/mysql/plugin/libcompress_sequence.so: only ET_DYN and ET_EXEC can be loaded)

What is ET_DYN? What is ET_EXEC?
What is happening?
How to solve the problem?

                        
Asked by Julien Ferté (71 rep)
Oct 27, 2016, 02:37 PM
Last activity: Oct 28, 2016, 09:53 AM
MySQL can't import a custom library for udf

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