I am compiling a C program with the SPARC RTEMS C compiler.
Using the Xlinker -M option, I am able to get a large memory map with a lot of things I don't recognize.
I have also tried using the RCC nm utility, which returns a slightly more readable symbol table. I assume that the location given by this utility for, say, printf, is the location where printf is in memory and that every program that calls printf will reach that location during execution. Is this a valid assumption?
Is there any way to get a list of locations for all the library/system functions? Also, when the linking is done, does it link just the functions that the executable calls, or is it all functions in the library? It seems to me to be the latter, given the number of things I found in the symbol table and memory map. Can I make it link only the required functions?
Thanks for your help.
Most often, when using a dynamic library, the nm utility will not be able to give you the exact answer. Binaries these days use what is known as relocatable addresses. These addresses change when they are mapped to the process' address space.
Using the Xlinker -M option, I am able to get a large memory map with a lot of things I don't recognize.
The linker map will usually have all symbols -- yours, the standard libraries, runtime hooks etc.
Is there any way to get a list of locations for all the library/system functions?
The headers are a good place to look.
Also, when the linking is done, does it link just the functions that the executable calls, or is it all functions in the library?
Linking does not necessarily mean that all symbols will be resolved (i.e. given an address). It depends on the type of binary you are creating.
Some compilers like gcc however, does allow you whether to create a non-relocatable binary or not. (For gcc you may check out exp files, dlltool etc.) Check with the appropriate documentation.