https://gcc.gnu.org/onlinedocs/gcc/Code-Gen-Options.html
-fpic- Generate position-independent code (PIC) suitable for use in a sharedlibrary, if supported for the target
machine. Such code accesses allconstant addresses through a global offset table (GOT). The dynamicloader resolves the GOT entries when the program starts (the dynamicloader is not part of GCC; it is part of the operating system). Ifthe GOT size for the linked
executable exceeds a machine-specificmaximum size, you get an error message from the linker indicating that-fpic does not work; in that case, recompile with
-fPICinstead. (These maximums are 8k on the SPARC, 28k on AArch64 and 32kon the m68k and RS/6000. The x86 has no such limit.)
Position-independent code requires special support, and therefore worksonly on certain machines. For the x86, GCC supports PIC for System Vbut not for the Sun 386i. Code generated for the IBM RS/6000 is alwaysposition-independent.
When this flag is set, the macros
__pic__and__PIC__are defined to 1. -fPIC- If supported for the target machine, emit position-independent code,suitable for dynamic linking and avoiding any limit on the size of theglobal offset table. This option makes a difference on AArch64, m68k,PowerPC
and SPARC.
Position-independent code requires special support, and therefore worksonly on certain machines.
When this flag is set, the macros
__pic__and__PIC__are defined to 2. -fpie-fPIE- These options are similar to
-fpic and -fPIC, butgenerated position independent code can be only linked into executables. Usually these options are used when
-pie GCC option isused during linking.
-fpie and -fPIE both define the macros
__pie__and__PIE__. The macros have the value 1for -fpie and 2 for -fPIE.