External Procedure Returns Bad String

Question

Hello,
I have an strange issue. I have an external procedure that returns an string but when i call it Oracle gets an string of zero's ascii chars. The length it`s ok but the content not.... The wrapper function is
PROCEDURE getString(returnValue OUT VARCHAR2) AS
LANGUAGE C
LIBRARY "UFDs"
NAME "getString"
WITH CONTEXT
PARAMETERS (
context,
returnValue STRING,
returnValue INDICATOR short,
returnValue LENGTH int
And the C code is
DLLIMPORT void getString(OCIExtProcContext* context,
char* returnValue,
short* returnValue_ind,
int* returnValue_len )
returnValue = (char*)OCIExtProcAllocCallMemory(context, 13);
//returnValue[0] = '\0';
strcpy(returnValue,"hello from c");
/* I have test this to gen a file an the string is OK
char buffer[500];
strcpy(buffer,"echo ");
strcat(buffer,returnValue);
strcat(buffer," >c:\\sal.txt");
system(buffer);
*returnValue_len = strlen(returnValue);
*returnValue_ind = (short)OCI_IND_NOTNULL;
return;
When i call this from oracle i get an string of size 12 but the string has invalid chars (zero ascii chars). Could it be a problem with charset conversion? Anybody has an example or idea?.
Regards

Answer 1

Can you please post your query / stored procedure you are using? Very possible reason includes one among your substring (within the concat) is null and making the final output to be null. Size, esp 800 shouldn't matter.