How can I link libc.a into a shared library in arm-linux use arm-none-linux-gnueabi-gcc

5
votes

In a project, my colleague create a static library, e.g liba.a, which linked with app.

In liba.a he overwrites the libc malloc() to his owner version.

I create a shared library libs.so which also linked with app.

The problem is when my libs.so linked with app, the malloc() used in my libs.so will be the one in liba.a, not the one in standard libc.so, this causes problems.

Then, I want static link the libc.a to my libs.so, I used -static -shared -fPIC flags for gcc.

But I always get arm-2012.03/bin/../lib/gcc/arm-none-linux-gnueabi/4.6.3/../../../../arm-none-linux-gnueabi/bin/ld: arm-2012.03/bin/../arm-none-linux-gnueabi/libc/usr/lib/libc.a(dl-tsd.o)(.text+0x14): R_ARM_TLS_LE32 relocation not permitted in shared object.

Does anyone have idea about it?

Thanks forward.

1
linuxlinkerarmshared-librarieslibc
I think -static -share should not be mixed.... - Jeyaram
The following text is copyed from ld.pdf from codesurgery: "-static Do not link against shared libraries. This is only meaningful on platforms for which shared libraries are supported. This option can be used with ‘-shared’. Doing so means that a shared library is being created but that all of the library’s external references must be resolved by pulling in entries from static libraries." - David Chyi
@DavidChyi: That only says -static and -shared can be mixed, but not that it's a good idea. Compilers in general have many options that are not a good idea to use for normal applications. They are important for special cases like compiling kernel, bootloader, microcontroller code and such. - Jan Hudec

1 Answers

2
votes

You can't, because code that goes in shared library must be compiled with -fPIC and code in static libraries isn't. If you managed to do it, the resulting executable would end up linked with libc multiple times, which would be really fragile anyway and probably crash sooner or later, so you shouldn't do it anyway. Therefore:

Don't. Dynamic libraries have to link against system libraries dynamically and any executable that links against any dynamic libraries also has to link system libraries dynamically.

I would also like to remind you, that linking GNU libc against non-GPL application statically is illegal, since LGPL only excepts dynamically linked code. This is on purpose to allow bugfixing the library without recompiling the executable for which source may not be available. It's rather common in Linux to upgrade shared libraries with bugfixed version without recompiling dependent executables; libc developers know how to do that.