最近有个共享库libraw的编译，需要将一个额外的第三方库静态库编译进共享库。这个第三方库是gpr库，用来让libraw.so支持gpr格式的图片。
gpr默认编译出来是静态库，但是没有加-fPIC选项，导致不能链接到共享库
/usr/bin/ld: /work/nas/gpr-1.1/staging/lib/libdng_sdk.a(dng_host.cpp.o): relocation R_X86_64_PC32 against symbol `_ZTV8dng_host' can not be used when making a shared object; recompile with -fPIC
但是如果一个符号只是内部用的话，可以不加-fPIC选项
使用 -Lstaging/lib -lgrp_sdk
编译libraw.so没有报错报错，但是在编译使用libraw.so的可执行程序时，报错了。
ld: lib/.libs/libraw.so: undefined reference to `InitImage'
$ readelf -a build/lib/.libs/libraw.so | grep InitImage
00000022f3b8 00c900000402 R_AARCH64_JUMP_SL 0000000000000000 InitImage + 0
201: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND InitImage
6374: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND InitImage
发现这个符号是UND，应该是静态库没有链接到共享库里面。
经过搜索发现了--whole-archive选项，手动运行编译命令，在静态库前后加上：
-Wl,--whole-archive /work/gpr-1.1/lib/libdng_sdk.a /work/gpr-1.1/lib/libgpr_sdk.a -Wl,--no-whole-archive \
运行后
$ readelf -a libraw.so.23.0.0 | grep InitImage
00000024f350 0bb700000402 R_AARCH64_JUMP_SL 00000000001707b0 InitImage + 0
2999: 00000000001707b0 44 FUNC GLOBAL DEFAULT 12 InitImage
6753: 00000000001707b0 44 FUNC GLOBAL DEFAULT 12 InitImage
备注：
静态库，可以-Lpath -lcommon，也可以直接指定路径，/path/libcommon.a
LD手册说的很详细
whole-archive是把静态库的所有object包含进去，通常用来将一个archive链接到shared libary
--whole-archive
For each archive mentioned on the command line after the ‘--whole-archive’
option, include every object file in the archive in the link, rather than searching
the archive for the required object files. This is normally used to turn an archive
file into a shared library, forcing every object to be included in the resulting
shared library. This option may be used more than once.
Two notes when using this option from gcc: First, gcc doesn’t know about this
option, so you have to use ‘-Wl,-whole-archive’. Second, don’t forget to use
‘-Wl,-no-whole-archive’ after your list of archives, because gcc will add its
own list of archives to your link and you may not want this flag to affect those
as well.
参考：
https://stackoverflow.com/questions/17558881/how-to-use-whole-archive-with-libtool