object file linking

[FlashBurn]

I link my source files with the option -i so that I can link "modules" in my loader to a kernel executable.

My problem is now that I have variables which I define as a global variable (outside from any function) and this variables use the section "COMMON" and I don´t know how to handle such variables. I would like to have that all symbols (functions and objects) are defined in relative to a section. The same problem applies to variables I define global and want to use in another source file, but in scope of the same module.

I hope you get the point.

sample code:

Code: Select all

uint32t foo;

void bar() {
 ...
}

If you compile this code and link it with "-i" and then do an "objdump -x file" the section to which "foo" applies is *COM* and this is my problem, better would be if it would be apply to .data or .bss!

[pcmattman]

Add -fno-common to your compile line.

[FlashBurn]

Thanks that solved my problem!

Is there a place where I can look for what this common section stuff is good?

[Solar]

The ld manual is spattered with references to COMMON, but doesn't give a detailed explanation.

There are two postings I found that, on first quick glance, seem to be very insightful:

How do linkers work and How a linker works (continued). I didn't check whether there are more parts to this.

[MasterLee]

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uint32t foo;

It could be better to add extern before the definition:

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extern uint32t foo;

[Solar]

Code: Select all

uint32t foo;

It could be better to add extern before the definition:

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extern uint32t foo;

Then it wouldn't be a definition anymore, would it?

[MasterLee]

Yes, but he could then define the symbols in the assembler files of the kernel

[FlashBurn]

As I´ve written, the option -fno-common solved the problem.