An optional output file from a linker program, also called a list file. This file can give you some very useful information about the nature of the compiled program.

Most linkers break the map file up into 3 parts:

  1. A listing, in no particular order that I can determine, of the load address of every piece of memory linked into the program, be it data or function address. This is usually used in conjunction with part 2.
  2. A listing, by ascending load address, of data location, along with the data type (code, read/write, or read-only) and the object file that it was linked out of. Parts 1 and 2 are useful in determining where the heck your code halted when you get a weird error message about stopping at instruction 0x23a219, or when you are using a debugger that won't overlay your original source on top of the assembly instructions.
  3. A breakdown, by object, of the code size and memory requirements associated with that object. This is broken down into code size, inline code, inline string data, constant data, initialized data, zero-init data, and debug data. At the end of the list, you will get a helpful subtotal of this data that is related to objects that you built and other libraries that you linked to, and a grand total for each of these columns.
I usually find the last column to be the most useful in analysis of code size and efficiency, when I need to figure out where to start my optimizations after getting everything up and running from the first pass.

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