You do not have to use PIC code in shared objects (as you have discovered you can use the -mimpure-text option to allow that). That said, non-PIC code in shared objects are more heavyweight. With PIC code, the text pages in memory are just direct memory mappings of the text pages on disk. This means … Read more
The answer depends on the platform. On most platforms, if output from readelf –relocs foo.o | egrep ‘(GOT|PLT|JU?MP_SLOT)’ is empty, then either foo.o was not compiled with -fPIC, or foo.o doesn’t contain any code where -fPIC matters.
Briefly, the error means that you can’t use a static library to be linked w/ a dynamic one. The correct way is to have a libavcodec compiled into a .so instead of .a, so the other .so library you are trying to build will link well. The shortest way to do so is to add … Read more
http://tldp.org/HOWTO/Program-Library-HOWTO/shared-libraries.html Use `-fPIC` or `-fpic` to generate position independent code. Whether to use `-fPIC` or `-fpic` to generate position independent code is target-dependent. The `-fPIC` choice always works, but may produce larger code than `-fpic` (mnemonic to remember this is that PIC is in a larger case, so it may produce larger amounts of code). … Read more
PIC stands for Position Independent Code. To quote man gcc: If supported for the target machine, emit position-independent code, suitable for dynamic linking and avoiding any limit on the size of the global offset table. This option makes a difference on AArch64, m68k, PowerPC and SPARC. Use this when building shared objects (*.so) on those … Read more
Position Independent Code means that the generated machine code is not dependent on being located at a specific address in order to work. E.g. jumps would be generated as relative rather than absolute. Pseudo-assembly: PIC: This would work whether the code was at address 100 or 1000 100: COMPARE REG1, REG2 101: JUMP_IF_EQUAL CURRENT+10 … … Read more