Strict function signature checking

IBM^® Informix^® 4GL (I4GL) is not very strict regarding function signature. With I4GL, you can, for example, define a function in module A that returns three values, and call that function in module B with a returning clause specifying two variables:

Module A:

FUNCTION func()
   RETURN "abc", "def", "ghi"
END FUNCTION

Module B (main):

MAIN
   DEFINE v1, v2 VARCHAR(100)
   CALL func() RETURNING v1, v2
END MAIN

The c4gl compiler (7.32) compiles and links these modules without error, but at execution time you get the following runtime error:

Program stopped at  "main.4gl", line number 3. 
FORMS statement error number -1320. 
A function has not returned the correct number of values 
expected by the calling function.

With Genero Business Development Language (BDL), the mistake will be detected at link time:

$ fgllink -o prog.42x main.42m module_a.42m
ERROR(-6200): Module 'main': The function module_a.func(0,3) will be 
called as func(0,2).

Similarly, I4GL does not detect an invalid number of parameters passed to a function defined in a different module:

Module A:

FUNCTION func( p )
   DEFINE p INTEGER
   DISPLAY p 
END FUNCTION

Module B (main):

MAIN
   CALL func(1,2)
END MAIN

The c4gl compiler (7.32) compiles and links these modules without error, but at execution time, you get the following runtime error:

Program stopped at  "main.4gl", line number 2. 
FORMS statement error number -1318. 
A parameter count mismatch has occurred between the calling 
function and the called function.

When using Genero BDL, the error will be detected at link time:

$ fgllink -o prog.42x main.42m module_a.42m
ERROR(-6200): Module 'main': The function module_a.func(1,0) will be 
called as func(2,0).

Note, however, that Genero BDL does not check function signatures when several RETURN instructions are found by the compiler. This is necessary in order to be compatible with I4GL. The next code example compiles and runs with both I4GL and BDL:

MAIN
   DEFINE v1, v2 VARCHAR(100)
   CALL func(1) RETURNING v1
   DISPLAY v1
   CALL func(2) RETURNING v1, v2
   DISPLAY v1, v2
END MAIN

FUNCTION func( n )
   DEFINE n INTEGER
   IF n == 1 THEN
      RETURN "abc"
   ELSE
      RETURN "abc", "def"
   END IF
END FUNCTION

However, this type of programming is not recommended.