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Is there anyway to "skip" an optimization level on Keil C51 ver 5.20? I continually get linker warnings about recursive calls. I have read app note 129 (many projects ago, and now do what it suggests as second nature). If I drop the optimizations down to "Dead Code Elimination" (the one below "Data Overlay"), all my linker warnings go away. As I have more RAM than I'll ever need in this project, I'd like to just skip overlay entirely, and avoid its problems. Unfortunately, code space is limited, and I cannot do without the other optimizations. I know I can do optimizations on a file by file basis (and have), but I'd like to avoid this if possible, and it still leaves that one file unoptimized. BTW: What exactly does the "enable variable overlay" under the linker menu do anyway... I cannot tell any difference from the map file. -nelson
The compiler optimizations have nothing to do with the warnings generated by the linker. If you want to disable variable overlaying, use the NOOVERLAY linker directive. Jon
The compiler optimizations have nothing to do with the warnings generated by the linker. then why does the warning go away when optimizations are turned nearly off. To me that means that something the compiler is doing affects how the linker is interpritting the object file. If you want to disable variable overlaying, use the NOOVERLAY linker directive This is the same as NOOL, which is what the linker box "enable variable overlay" adds when I leave it unchecked. The map file is identical (I diffed the 2 just now) with this option checked and unchecked. Purhaps I don't understand variable overlays? I was under the impression that if overlay is enabled, then my xdata space would use less space (and I know that I have multiple functions that CANNOT be executed at the same time and don't use static variables)
opt level xdata end 6 0x57B linker warning 5 0x57B linker warning 4 0x57B linker warning 3 0x587 linker warning 2 0x587 linker warning 1 0x7C8 no linker warning
What memory model are you using? That determines where the compiler puts variables - including locals - by default. If you're using a model which defaults to other than XDATA, then overlaying or not may well not affect your XDATA space.
"The compiler optimizations have nothing to do with the warnings generated by the linker." This is not entirely true; different Compiler optimisations will produce different objects, with the result that certain Linker warnings may or may not be raised; eg, the following is on p260 of the "Assembler and Utilities User's Guide 07.2000:" "C code that is translated with the Cx51 compiler directive OPTIMIZE (1) does not use the relocation type OVERLAYABLE. Therefore the local data segments of this code portions (sic) cannot be overlaid." As the original post was due to problems with overlays, the choice of optimisation level could affect the generation (or not) of overlay-related Linker warnings!