Q42475: BASIC Uses ALIAS to DECLARE C Routines with Underscore in Name

Article: Q42475
Product(s): See article
Version(s): 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | B_BasicCom | mspl13_basic
Last Modified: 30-MAY-1990

To call a Microsoft C routine from QuickBASIC, the C routine must
first be declared using a DECLARE statement. If the C routine name
contains an embedded underscore, which is improper syntax in
QuickBASIC, you must use the ALIAS clause to give it a valid BASIC
name.

This information applies to Microsoft QuickBASIC versions 4.00, 4.00b,
and 4.50, Microsoft BASIC Compiler versions 6.00 and 6.00b, and
Microsoft BASIC Professional Development System (PDS) version 7.00.
The references to DECLARE, ALIAS, and CDECL can be found on Pages 142
to 146 of the "Microsoft QuickBASIC 4.0: BASIC Language Reference"
manual.

C functions added to a library or Quick library have an underscore
added to the front of the function name (that is, "foo_bar" will
become "_foo_bar" in a library). When you DECLARE a C routine in a
BASIC program, you must use the CDECL clause, which automatically
adjusts for the underscore at the front of the routine name.

However, if you want to use the ALIAS clause to DECLARE a C function
that has an embedded underscore (for example, "foo_bar"), the CDECL
clause will not add the underscore automatically to the front of the
ALIAS name.

The following is an example:

REM *** BASIC program to call foo_bar ***
DECLARE SUB foobar CDECL ALIAS "_foo_bar"
CALL foobar
END

/* C function with embedded underscore */
void foo_bar()
{
  putch('A');
}

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