pec@necntc.nec.com (Paul Cohen) (02/21/90)
I need some help with creating a far code segment under Microsoft C in the Compact memory model. I have a program which has just slightly too large a code size to fit in one segment. It has one function which is executed only once so putting it into another segment seems a way to avoid changing to the Large memory model (which slows down execution noticeably). My question is how to do this. Simply declaring the function "far" doesn't do the trick. I have several hypotheses about what more might be needed, but would prefer to avoid the trial and error approach. My hypotheses are: 1. The far function should be in a separate source file from any near functions. 2. All functions called by the far function should be themselves declared as far functions. Can someone comment on these hypotheses or suggest any other magic that might be needed?
gunther@jhunix.HCF.JHU.EDU (Gunther Wil Anderson) (02/24/90)
In article <28396@necntc.nec.com> pec@necntc.nec.com (Paul Cohen) writes: >I have a program which has just slightly too large a code size to fit in >one segment. It has one function which is executed only once so putting >it into another segment seems a way to avoid changing to the Large >memory model (which slows down execution noticeably). Use overlaying. Read it up in your compiler manual or dos manual, compile the offending routine in a separate file, and specify it as not part of the permanent code. You may need to place something alse in that state so there is some space for the two to swap between them. Gunther W. Anderson gunther@jhunix.hcf.jhu.edu
pec@necntc.nec.com (Paul Cohen) (03/02/90)
In article <4327@jhunix.HCF.JHU.EDU> eisen@jhunix.UUCP (Gunther Wil Anderson) writes: >>In article <28396@necntc.nec.com> pec@necntc.nec.com (Paul Cohen) writes: >>I have a program which has just slightly too large a code size to fit in >>one segment. It has one function which is executed only once so putting >>it into another segment seems a way to avoid changing to the Large >>memory model (which slows down execution noticeably). >Use overlaying. Read it up in your compiler manual or dos manual, >compile the offending routine in a separate file, and specify it as >not part of the permanent code. You may need to place something alse >in that state so there is some space for the two to swap between them. Thanks for the suggestion, but I prefer not to use overlays because of the extra file and extra overhead involved. I also received some mail from Microsoft, giving some incorrect advice on the matter. Since it appears that I am not the only one who did not know how to do this, let me explain what I have discovered since my original posting. As I suspected, it is possible to put one function into a far segment and stay with the SMALL/COMPACT model for the rest of the program. It is not even difficult to do. I put the one "far" function into its own separate source file. In linking, this particular module HAD TO BE LISTED AS THE LAST .obj file file. Otherwise LINK would put it into the same segment as the rest of the program and then complain that there was not enough space. Listing a particular .obj file last required some trickery because of a pecular shortcomming in Microsoft's MAKE utility. Because this MAKE utility permits only fairly short lines it was not possible for me to list all of the object files separately on the LINK command line, but instead had to use the "*.obj" syntax. In order to control which file appeared last, I put it into a separate directory so that I could specify it separately, after the *.obj specification.