Object files (or object code) are machine code files generated by a compiler from source code. The difference with an executable is that the object file isn’t linked, so references to functions, symbols, etc aren’t defined yet (their memory addresses is basically left blank). When you compile a C file with GCC: gcc -Wall -o … Read more
A .LIB file is a collection of .OBJ files concatenated together with an index. There should be no difference in how the linker treats either.
Compiling to object files first is called separate compilation. There are many advantages and a few drawbacks. Advantages: easy to transform object files (.o) to libraries and link to them later many people can work on different source files at the same time faster compiling (you don’t compile the same files again and again when … Read more
This is a simple problem. You just forgot the semi colon at the end of your header file. The compiler errors you get for missing the semi colon at the end of a class definition are very hard to relate to the actual problem – just get in the habit of checking that when you … Read more
Let’s say you have the following C source file, call it name.c #include <stdio.h> #include <stdlib.h> void print_name(const char * name) { printf(“My name is %s\n”, name); } When you compile it, with cc name.c you generate name.o. The .o contains the compiled code and data for all functions and variables defined in name.c, as … Read more
On gcc, use ar -t. -t option of the gnu archiver (ar) writes a table of contents of archive to the standard output. Only the files specified by the file operands shall be included in the written list. If no file operands are specified, all files in archive shall be included in the order of … Read more
Passing -relocatable or -r to ld will create an object that is suitable as input of ld. $ ld -relocatable a.o b.o -o c.o $ gcc c.o other.o -o executable $ ./executable The generated file is of the same type as the original .o files. $ file a.o a.o: ELF 32-bit LSB relocatable, Intel 80386, … Read more
Instead of nm, you can use the powerful objdump. See the man page for details. Try objdump -t myfile or objdump -T myfile. With the -C flag you can also demangle C++ names, like nm does.
An object file is the real output from the compilation phase. It’s mostly machine code, but has info that allows a linker to see what symbols are in it as well as symbols it requires in order to work. (For reference, “symbols” are basically names of global objects, functions, etc.) A linker takes all these … Read more