編譯so 文件 gcc -shared -fPIC

-fPIC 是什么意思呢。。。

看GCC手冊

-fpic Generate position-independent code (PIC) suitable for use in a shared library,

if supported for the target machine. Such code accesses all constant addresses

through a global offset table (GOT). The dynamic loader resolves the GOT

entries when the program starts (the dynamic loader is not part of GCC; it

is part of the operating system). If the GOT size for the linked executable

exceeds a machine-specific maximum size, you get an error message from the

linker indicating that ‘-fpic’ does not work; in that case, recompile with ‘-fPIC’

instead. (These maximums are 8k on the SPARC and 32k on the m68k and

RS/6000. The 386 has no such limit.)

Position-independent code requires special support, and therefore works only on

certain machines. For the 386, GCC supports PIC for System V but not for the

Sun 386i. Code generated for the IBM RS/6000 is always position-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 the global offset table.

This option makes a difference on the m68k, PowerPC and SPARC.

Position-independent code requires special support, and therefore works only

on certain machines.

When this flag is set, the macros __pic__ and __PIC__ are defined to 2.

也就是生成與位置無關(guān)的代碼 windows上面是通過加一個重定位表來實現(xiàn)的 。。

linux 和? windows類似 使用了個 GOT 全局偏移描述表來實習(xí)動態(tài)的定位 、、

系統(tǒng)加載的時候 會根據(jù)加載的地址 修正偏移表里的偏移? 這樣就實現(xiàn)了代碼的執(zhí)行與代碼所在的位置位置無關(guān)。。

怎么使用動態(tài)鏈接庫呢 shared object

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