旧库路径在OS X 10.9下不工作

我一直在试图弄清楚为什么g++不能将程序链接到犰狳库。问题很简单:

macbook-pro:arma-xc jmlopez$ g++-4.9 inputs-arma.cpp -larmadillo
ld: library not found for -larmadillo
collect2: error: ld returned 1 exit status

也许我确实指定了库应该在哪里

macbook-pro:arma-xc jmlopez$ ls -l /usr/lib/libarma*
-rwxr-xr-x  1 root  wheel  37928 Aug 18 14:30 /usr/lib/libarmadillo.4.32.2.dylib
lrwxr-xr-x  1 root  wheel     25 Aug 18 14:30 /usr/lib/libarmadillo.4.dylib -> libarmadillo.4.32.2.dylib
lrwxr-xr-x  1 root  wheel     20 Aug 18 14:30 /usr/lib/libarmadillo.dylib -> libarmadillo.4.dylib

让我们再试一次

macbook-pro:arma-xc jmlopez$ g++-4.9 -L/usr/lib inputs-arma.cpp -larmadillo
ld: library not found for -larmadillo
collect2: error: ld returned 1 exit status

好吧，这并没有解决问题。让我们看看发生了什么，为此我们将使用-v选项，它将生成一些长输出。

macbook-pro:arma-xc jmlopez$ g++-4.9 -L/usr/lib inputs-arma.cpp -larmadillo -v
Using built-in specs.
COLLECT_GCC=g++-4.9
COLLECT_LTO_WRAPPER=/usr/local/Cellar/gcc/4.9.1/libexec/gcc/x86_64-apple-darwin13.3.0/4.9.1/lto-wrapper
Target: x86_64-apple-darwin13.3.0
Configured with: ../configure --build=x86_64-apple-darwin13.3.0 --prefix=/usr/local/Cellar/gcc/4.9.1 --enable-languages=c,c++,objc,obj-c++,fortran --program-suffix=-4.9 --with-gmp=/usr/local/opt/gmp --with-mpfr=/usr/local/opt/mpfr --with-mpc=/usr/local/opt/libmpc --with-cloog=/usr/local/opt/cloog --with-isl=/usr/local/opt/isl --with-system-zlib --enable-version-specific-runtime-libs --enable-libstdcxx-time=yes --enable-stage1-checking --enable-checking=release --enable-lto --disable-werror --with-pkgversion='Homebrew gcc 4.9.1' --with-bugurl=https://github.com/Homebrew/homebrew/issues --enable-plugin --disable-nls --enable-multilib --with-native-system-header-dir=/usr/include --with-sysroot=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk
Thread model: posix
gcc version 4.9.1 (Homebrew gcc 4.9.1) 
COLLECT_GCC_OPTIONS='-mmacosx-version-min=10.9.3' '-L/usr/lib' '-v' '-shared-libgcc' '-mtune=core2'
 /usr/local/Cellar/gcc/4.9.1/libexec/gcc/x86_64-apple-darwin13.3.0/4.9.1/cc1plus -quiet -v -D__DYNAMIC__ inputs-arma.cpp -fPIC -quiet -dumpbase inputs-arma.cpp -mmacosx-version-min=10.9.3 -mtune=core2 -auxbase inputs-arma -version -o /var/folders/6x/ss29s2r51z5cv0_g1ffx0c0c0000gn/T//ccApA95Q.s
GNU C++ (Homebrew gcc 4.9.1) version 4.9.1 (x86_64-apple-darwin13.3.0)
    compiled by GNU C version 4.9.1, GMP version 6.0.0, MPFR version 3.1.2-p8, MPC version 1.0.2
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
ignoring nonexistent directory "/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/local/include"
ignoring nonexistent directory "/usr/local/Cellar/gcc/4.9.1/lib/gcc/x86_64-apple-darwin13.3.0/4.9.1/../../../../x86_64-apple-darwin13.3.0/include"
ignoring nonexistent directory "/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/Library/Frameworks"
#include "..." search starts here:
#include <...> search starts here:
 /Users/jmlopez/github/excentury/excentury/extern/include
 /usr/include
 /usr/local/Cellar/gcc/4.9.1/lib/gcc/x86_64-apple-darwin13.3.0/4.9.1/include/c++
 /usr/local/Cellar/gcc/4.9.1/lib/gcc/x86_64-apple-darwin13.3.0/4.9.1/include/c++/x86_64-apple-darwin13.3.0
 /usr/local/Cellar/gcc/4.9.1/lib/gcc/x86_64-apple-darwin13.3.0/4.9.1/include/c++/backward
 /usr/local/Cellar/gcc/4.9.1/lib/gcc/x86_64-apple-darwin13.3.0/4.9.1/include
 /usr/local/Cellar/gcc/4.9.1/lib/gcc/x86_64-apple-darwin13.3.0/4.9.1/include-fixed
 /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/include
 /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/System/Library/Frameworks
End of search list.
GNU C++ (Homebrew gcc 4.9.1) version 4.9.1 (x86_64-apple-darwin13.3.0)
    compiled by GNU C version 4.9.1, GMP version 6.0.0, MPFR version 3.1.2-p8, MPC version 1.0.2
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: 5a051bcf2be886a5c6eb8ba33f338693
COLLECT_GCC_OPTIONS='-mmacosx-version-min=10.9.3' '-L/usr/lib' '-v' '-shared-libgcc' '-mtune=core2'
 as -arch x86_64 -force_cpusubtype_ALL -o /var/folders/6x/ss29s2r51z5cv0_g1ffx0c0c0000gn/T//cchm9rVF.o /var/folders/6x/ss29s2r51z5cv0_g1ffx0c0c0000gn/T//ccApA95Q.s
COMPILER_PATH=/usr/local/Cellar/gcc/4.9.1/libexec/gcc/x86_64-apple-darwin13.3.0/4.9.1/:/usr/local/Cellar/gcc/4.9.1/libexec/gcc/x86_64-apple-darwin13.3.0/4.9.1/:/usr/local/Cellar/gcc/4.9.1/libexec/gcc/x86_64-apple-darwin13.3.0/:/usr/local/Cellar/gcc/4.9.1/lib/gcc/x86_64-apple-darwin13.3.0/4.9.1/:/usr/local/Cellar/gcc/4.9.1/lib/gcc/x86_64-apple-darwin13.3.0/
LIBRARY_PATH=/usr/lib/:/usr/local/Cellar/gcc/4.9.1/lib/gcc/x86_64-apple-darwin13.3.0/4.9.1/:/usr/local/Cellar/gcc/4.9.1/lib/gcc/x86_64-apple-darwin13.3.0/4.9.1/../../../:/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/lib/
COLLECT_GCC_OPTIONS='-mmacosx-version-min=10.9.3' '-L/usr/lib' '-v' '-shared-libgcc' '-mtune=core2'
 /usr/local/Cellar/gcc/4.9.1/libexec/gcc/x86_64-apple-darwin13.3.0/4.9.1/collect2 -dynamic -arch x86_64 -macosx_version_min 10.9.3 -syslibroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk -weak_reference_mismatches non-weak -o a.out -L/usr/lib -L/usr/local/Cellar/gcc/4.9.1/lib/gcc/x86_64-apple-darwin13.3.0/4.9.1 -L/usr/local/Cellar/gcc/4.9.1/lib/gcc/x86_64-apple-darwin13.3.0/4.9.1/../../.. -L/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/lib /var/folders/6x/ss29s2r51z5cv0_g1ffx0c0c0000gn/T//cchm9rVF.o -larmadillo -lstdc++ -no_compact_unwind -lSystem -lgcc_ext.10.5 -lgcc -lSystem -v
collect2 version 4.9.1
/usr/bin/ld -dynamic -arch x86_64 -macosx_version_min 10.9.3 -syslibroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk -weak_reference_mismatches non-weak -o a.out -L/usr/lib -L/usr/local/Cellar/gcc/4.9.1/lib/gcc/x86_64-apple-darwin13.3.0/4.9.1 -L/usr/local/Cellar/gcc/4.9.1/lib/gcc/x86_64-apple-darwin13.3.0/4.9.1/../../.. -L/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/lib /var/folders/6x/ss29s2r51z5cv0_g1ffx0c0c0000gn/T//cchm9rVF.o -larmadillo -lstdc++ -no_compact_unwind -lSystem -lgcc_ext.10.5 -lgcc -lSystem -v
@(#)PROGRAM:ld  PROJECT:ld64-236.4
configured to support archs: armv6 armv7 armv7s arm64 i386 x86_64 armv6m armv7m armv7em
Library search paths:
    /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/lib
    /usr/local/Cellar/gcc/4.9.1/lib/gcc/x86_64-apple-darwin13.3.0/4.9.1
    /usr/local/Cellar/gcc/4.9.1/lib
    /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/lib
    /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/lib
Framework search paths:
    /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/System/Library/Frameworks/
ld: library not found for -larmadillo
collect2: error: ld returned 1 exit status

重要信息在这里:

Library search paths:
    /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/lib
    /usr/local/Cellar/gcc/4.9.1/lib/gcc/x86_64-apple-darwin13.3.0/4.9.1
    /usr/local/Cellar/gcc/4.9.1/lib
    /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/lib
    /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/lib

不知何故，它不是在寻找/usr/lib。我已尝试先指定此目录导出变量LD_LIBRARY_PATH

macbook-pro:arma-xc jmlopez$ export LD_LIBRARY_PATH=/usr/lib
macbook-pro:arma-xc jmlopez$ g++-4.9 -L/usr/lib inputs-arma.cpp -larmadillo
ld: library not found for -larmadillo
collect2: error: ld returned 1 exit status

没有运气。最后，考虑到ld可能被破坏，我这样做:

macbook-pro:arma-xc jmlopez$ ln -s /usr/lib/libarmadillo.dylib /usr/local/Cellar/gcc/4.9.1/lib/libarmadillo.dylib
macbook-pro:arma-xc jmlopez$ g++-4.9 inputs-arma.cpp -larmadillo

现在它工作了。我不确定我的系统是否有问题，但似乎我没有办法为ld指定其他路径来查找我的库。相反，我必须使用以下任何一种:

Library search paths:
    /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/lib
    /usr/local/Cellar/gcc/4.9.1/lib/gcc/x86_64-apple-darwin13.3.0/4.9.1
    /usr/local/Cellar/gcc/4.9.1/lib
    /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/lib
    /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/lib

有办法解决这个问题吗?请注意，我使用的g++从自制，因为我认为一个自带的xcode是坏的。无论如何，运气不好，至少自制g++告诉我库被搜索的路径。

更新:

我决定看看是否可以添加另一个路径:

g++-4.9 -L/Users/jmlopez/ -L/Users/jmlopez/Desktop -L/usr/lib inputs-arma.cpp -larmadillo -v

现在它搜索库的路径列表是:

Library search paths:
    /Users/jmlopez/
    /Users/jmlopez/Desktop
    /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/lib
    /usr/local/Cellar/gcc/4.9.1/lib/gcc/x86_64-apple-darwin13.3.0/4.9.1
    /usr/local/Cellar/gcc/4.9.1/lib
    /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/lib
    /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/lib

/usr/lib在哪里?这个目录有什么特别之处，以至于ld拒绝查看这个目录。它在我的主目录和我的桌面中搜索。我尝试添加/usr/local，它将其添加到目录列表中。我现在开始怀疑目录的权限…什么好主意吗?