Native Development

[rcmaniac25]

One of the projects I'm working on involves a static library for a bunch of "boilerplate code", a shared library for specific functionality (uses static lib), and an executable for, well, execution (uses static lib and shared lib).

The static library compiler just fine. But when I try to compile the shared library, which links to the static library, I get the following error:

C:\bbndk-2.1.0-beta1\host\win32\x86\usr\bin\ntoarm-ld: {static lib path}.a({object file}.o): relocation R_ARM_MOVW_ABS_NC against `__stack_chk_guard' can not be used when making a shared object; recompile with -fPIC

 Any knowledge of what has happened?

I know I can simply specify -fPIC and be done with it, but I admittidly don't know if I specify it for the static library or the shared library. I think shared.

Edit: Ok, I now know I need to specify it on the static library.

Regardless, does anyone know what might have caused something like this and is -fPIC the only way to fix it?

[selom]

Hello,

-fpic and -fPIC generate position independent code, a requirement for shared libraries. If you were asking about what the __stack_check_guard is, you can find more information about it at http://wiki.osdev.org/GCC_Stack_Smashing_Protector

Cheers

Selom

[rcmaniac25]

I understand that. What I am interested in knowing is what might have caused me to get the error I specified in my original post, like what kind of code.

I mentioned in an edit in my original post that I found I needed to specify it on the static library. Is specifying -fPIC on the static library the only way to get around this error short of a code rewrite (if it is even caused by some code).

[selom · Accepted solution]

Hello again,

it's not caused by your code. The stack smashing protector is automatically inserted by the compiler to prevent stack overflows, without -fPIC your lib cannot be loaded.

Cheers

Selom

[rcmaniac25]

Ok, so it "just is" and I should always use -fPIC for a static library.

[selom]

Indeed, plus you get buffer overflow protection for free. I highly recommend it for all apps.

However if you're the tinkering type, you can try disabling that option in gcc by removing the -fstack-protector-all compile file in the project properties->c/c++ build->settings->tool settings->QCC Compiler->Output control and unchecking the "Enhanced Security" option.

Cheers

Selom

[rcmaniac25]

Extra security for free? Why disable it?