带有Fat库的OS X上体系结构x86_64的未定义符号 [英] Undefined symbols for architecture x86_64 on OS X with fat library

问题描述

我自己从源代码构建了libcrypto.a和libssl.a，并为OpenSSL的配置脚本指定了darwin64-x86_64-cc(对于64位)和darwin-i386-cc(对于32位).
用lipo创建胖库，并将它们作为依赖项添加到我的Xcode项目中.

I have build libcrypto.a and libssl.a myself from source, specifying darwin64-x86_64-cc (for 64-bit) and darwin-i386-cc (for 32-bit) to OpenSSL's configure script.
Created the fat libraries with lipo and added them as a dependency in my Xcode project.

但是，我遇到了未定义的符号错误:

However, I'am getting an undefined symbol error:

undefined symbols for architecture x86_64:
  "_OPENSSL_ia32cap_P", referenced from:
      _AES_cbc_encrypt in libcrypto.a(aes-x86_64.o)
ld: symbol(s) not found for architecture x86_64

注意:不过，使用相同的技术在iOS上效果很好.

Note: Using the same technique works fine for iOS, though.

lipo -detailed_info libcrypto.a显示:

Fat header in: libcrypto.a
fat_magic 0xcafebabe
nfat_arch 2
architecture i386
    cputype CPU_TYPE_I386
    cpusubtype CPU_SUBTYPE_I386_ALL
    offset 48
    size 2700624
    align 2^2 (4)
architecture x86_64
    cputype CPU_TYPE_X86_64
    cpusubtype CPU_SUBTYPE_X86_64_ALL
    offset 2700672
    size 3938432
    align 2^2 (4)

推荐答案

在静态库的情况下，这似乎是x64的代码生成器中的错误.

It looks to be a bug in the code generator for x64 in the static library case.

最简单的非补丁openssl更改解决方法是在代码中的某个位置添加对OPENSSL_cleanse的引用，即使未使用它也是如此.这样可以修正链接时间参考.

The easiest, non patch openssl change workaround is to add a reference to OPENSSL_cleanse somewhere in your code, even if it's not used. That will fix up the link-time reference.

实际上是在某些汇编代码中引用了该符号.

What's actually happening is that the symbol is being referenced in some assembly code.

汇编代码只是说_OPENSSL_ia32cap_P是一个外部符号，而没有使交叉链接表明需要链接它.这对libcrypto.dylib有用，因为在生成.dylib时引用已解析.文件;但是，在.a情况下，引用永远不会解析，因为实际上包含符号的唯一代码是x86_64cpuid.o，只有在使用该.o提供的任何例程时，该链接才会被链接.

The assembly code simply says that _OPENSSL_ia32cap_P is an extern symbol, without making the cross-link to state that it needs to be linked in. This works for libcrypto.dylib because the reference is resolved when generating the .dylib file; however the reference is never resolved in the .a case because the only code that actually contains the symbol is x86_64cpuid.o, which only gets linked in if you use any of the routines provided by that .o.

此文件中的符号包含OPENSSL_cleanse，因此，如果您引用此例程，则该链接有效.

Symbols in this file includes OPENSSL_cleanse, so if you reference this routine, the link works.

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