get the function's prototype from elf file

[np2k]

Hi all.
I've an ELF file (exec)...i'm interested in getting a the function prototype of the "myfunc"...
can you help me?

[JohnGraham]

You can't retrieve the function prototype from an ELF file, with the possible exception of doing it through disassembly, but that would be tricky and error-prone.

You need a header file, really.

[np2k]

a header file? i have only the elf file....

[Rubberman]

It depends upon whether or not it has been stripped of debugging information. Is it a .o, .a, .so, or is it an executable file?

[np2k]

it's an exec file...i solved the problem....simply: the file is compiled with -g option so i can use a gdb "call" to see the prototype of my function :P

[Rubberman]

it's an exec file...i solved the problem....simply: the file is compiled with -g option so i can use a gdb "call" to see the prototype of my function :P

Actually, an executable is not ELF - it is binary code. However, that would have been my suggestion, to use gdb, if you confirmed that. It's good that you figured that approach out on your own.

[np2k]

Actually, an executable is not ELF - it is binary code.

what? the exec's format is not ELF?

np2k@serena:~/Desktop$ file something.smt 
something.smt: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), dynamically linked
(uses shared libs), for GNU/Linux 2.6.15, stripped

From wiki:

In computing, the Executable and Linkable Format (ELF, formerly called Extensible Linking Format) is a common standard file format for executables, object code, shared libraries, and core dumps

I'm confused

[JohnGraham]

what? the exec's format is not ELF?

Yeah, I'm not quite sure what Rubberman's getting at - the standard file format for executables on a modern Linux system is indeed ELF, which is designed to be used for shared libraries, object files and executables.

[Rubberman]

ELF is an intermediate format that is platform-neutral. The linker will take the ELF modules and convert them to binary machine-executable code. COFF (Common Object File Format) is another, older intermediate format that served the same purposes as ELF. It's possible (perhaps even likely) that the system loader can convert ELF modules dynamically to machine code. Since shared libraries are generally (on Linux at least) ELF modules, this actually makes sense. So, you executable may have been an ELF module. Without looking at it I can't say for sure.

[Rubberman]

Yeah, I'm not quite sure what Rubberman's getting at - the standard file format for executables on a modern Linux system is indeed ELF, which is designed to be used for shared libraries, object files and executables.

Yes, they generally are, but they don't have to be, and in fact if a program is fully linked statically (no shared libraries) I don't think the resulting binary is ELF. Of course, I'm always happy to be disabused of my ignorance...