[Ken Streeter]

Originally Posted by interfect

Does anyone have an implementation of malloc? We really need some way to dynamically allocate memory, as we're running up against the 256 byte global per file limit.

There are a few different alternatives for getting around the 256 byte global per file limit.

If you need additional storage for variables, one option is to use the "#pragma" directive to explicitly put data into different memory "sections". Earlier this season, there was a previous Chief Delphi thread which discussed this approach. Another posting describing this technique can be found in this thread from 2006. Whether you use the "idata" or "udata" declarations depends upon whether or not the variables you are using are "initialized data" or "uninitialized data."

For more information on the use of the "#pragma" directive, you'll need to look at the MPLAB C18 Users manual. I don't know where to find the manual for version 2.4 of the compiler, but the MPLAB website does have the manual for the newer 3.0 version.

In the above manual, see pages 20-26 for information on using the #pragma directive to be able to use more than one memory section for a given file.

If the storage you need is for "constant" data (for example, a large lookup table that is initialized to certain values, but then never changed) you can declare the "variables" (the ones that are constants that never change) with the "rom" qualifier so that these "variables" are actually stored in program memory. In that way, you can store much larger lookup tables, as long as the code never changes them dynamically. (The lookup tables would need to be changed by recompiling in that case.)

Hopefully one of these approaches will work for you!