Compiling and linking C code without any additional data in output file

Question

I am asking for help by professionals because of lack of my knowledge in using GCC and ld.I'm writing OS for educational purposes, and i have a problem with compiling and linking C code. To be honest, the is no any problem, but I'm confused by the unncessary data in output files generated by the GCC and LD like

GCC: (Ubuntu/Linaro 4.6.3-1ubuntu5) 4.6.3 symtab..strtab..shstrtab..text..eh_frame..data..comment
.ELF..|

and etc. I really need to know which parameters use both with gcc and ld to reduce this unuseful (for my OS) data

Parameters I used before: -c -nostdlib -nostdinc -fno-builtin -fno-stack-protector -fstrength-reduce -finline-functions I also use linker script to organise segments.

I tried objcopy to reduce such blocks as .comment and .note from output, for me it was the best solution

objcopy -R .note -R .comment -S -O binary kernel.o kernel.bin

muppetlabs.com/~breadbox/software/tiny/teensy.html

pmg
– pmg

2012-07-16 15:56:28 +00:00
Commented Jul 16, 2012 at 15:56 — pmg
– pmg, Commented Jul 16, 2012 at 15:56

Viktor Latypov · Accepted Answer · 2012-07-16 16:29:25Z

4

Split you compilation and linking stages. Use the "-s" option for GCC to reduce .o files. (the link in pmg's comment is of particular interest, though not related to linker scripts)

The linker's script for a simple kernel is described here (tutorial for building the kernel using LD).

Use the

ld -T <yourscript> <objectfilelist> -o kernel.bin

command to get the desired binary.

edited Jul 16, 2012 at 16:29

answered Jul 16, 2012 at 16:11

Viktor Latypov

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hrust · Accepted Answer · 2015-10-25 13:19:30Z

1

Problem can be solved with the linker script. Using /DISCARD/ block. Ld manual says that this block excludes everything listed in it from final output.

So I've inserted this block after the .text, .data and .bss blocks

/DISCARD/ : 
{
    *(.comment)
    *(.eh_frame)
    *(.note.GNU-stack)
}

As well as this line in the very beginning of my linker script to make output a plane binary file.

OUTPUT_FORMAT("binary")

Therefore, I do not need to use objcopy anymore.

answered Oct 25, 2015 at 13:19

hrust

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