SQL keyword protection

If the code in the files is passed unprotected to the C preprocessor before it is passed to the preprocessor, certain SQL keywords might be analyzed by the C preprocessor, which causes unintended results. In the following example, the SQL keyword NULL is replaced by the C preprocessor with the value zero, which creates a valid SQL statement, but one which inserts a value into the orders table other than the value that the programmer intended:

EXEC SQL insert into orders (shipcharge) values (NULL);

When a user gives the option to run the C preprocessor before the preprocessor, the utility eprotect runs before the C preprocessor runs on the source file. The eprotect utility adds a prefix to any SQL keyword that occurs in an SQL statement with the prefix SQLKEYWORD_. This prefix is affixed on all SQL keywords inside SQL statements that begin with the EXEC SQL directive and end with a semicolon. When the source file that contains the select statement mentioned earlier is passed to the C preprocessor, the SELECT statement has the following form:

EXEC SQL SQLKEYWORD_insert SQLKEYWORD_into orders (order_num) 
SQLKEYWORD_values (SQLKEYWORD_NULL);