From the COBOL Cafe: https://www.ibm.com/developerworks/community/forums/html/topic?id=e055e63f-4e61-4502-b04c-db9b3d89d213
Allan Kielstra, from Markham, on a question of whether COBOL V5+ uses the FASTLINK calling convention. 'This is a bit confusing. Even I was confused while I was implementing it. :-) There are a number of variants of the basic "OS Linkage." That's the linkage that uses R1 as a pointer to a block of incoming arguments (or outgoing parameters.) One of those variants is called "C private," and it is the one that is used by C. To tell that you are C private, you start by "pretending" that you are fastlink. All the magic is here in the PPA1: 0003F8 90 =AL1(144) Flags That's the program flags at offset hex 18 in the PPA1. The value 1 in the top bit says "fastlink stack frame layout." But that is "waved off" by the value 001 in the next three bits. That means "C private" convention. So we always generate a 9x for that field of the PPA1. (In fact a 90.) That note about returning a doubleword binary item is something that did change between V4 and V5. The C private calling convention requires that such items be returned in storage whose address is passed as a hidden first argument. The V4 compiler didn't implement that quite right but it did everything else correctly for C private. The V5/V6 compiler also implements C private and it adheres to the specification correctly even in this case. So the bottom line is: we use C private and not fastlink for COBOL.' ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
