LD

命令行选项

@2019-02-20 新版功能: 创建

gcc 使用 -Wl, 前缀，例如 -Wl,--as-needed。

• --as-needed

  允许链接器忽略不需要的库。其他两个参数：

  • --no-undefined
  • --no-allow-shlib-undefined

  参考 Unresolved symbols in shared libraries 和 Project:Quality Assurance/As-needed。

环境变量

• LD_DEBUG

  @2011-03-09 新版功能: 创建

  If LD_DEBUG is set, the linker will dump many useful debug information. See help below:

  $ LD_DEBUG=help id
  Valid options for the LD_DEBUG environment variable are:
  
    libs        display library search paths
    reloc       display relocation processing
    files       display progress for input file
    symbols     display symbol table processing
    bindings    display information about symbol binding
    versions    display version dependencies
    scopes      display scope information
    all         all previous options combined
    statistics  display relocation statistics
    unused      determined unused DSOs
    help        display this help message and exit
  
  To direct the debugging output into a file instead of standard output
  a filename can be specified using the LD_DEBUG_OUTPUT environment variable.
  

  See following example for a common error cannot open shared object file: No such file or directory:

  $ vim
  vim: error while loading shared libraries: libgcc_s.so.1: cannot open shared object file: No such file or directory
  $ LD_DEBUG=libs vim
       23579:     find library=libSM.so.6 [0]; searching
       ...
       23579:     find library=libgcc_s.so.1 [0]; searching
       23579:      search cache=/etc/ld.so.cache
       23579:       trying file=/usr/lib/gcc/x86_64-pc-linux-gnu/7.3.0/libgcc_s.so.1
       23579:      search path=/lib64/tls/x86_64/x86_64:/lib64/tls/x86_64:/lib64/tls/x86_64:/lib64/tls:/lib64/x86_64/x86_64:/lib64/x86_64:/lib64/x86_64:/lib64:/usr/lib64/tls/x86_64/x86_64:/usr/lib64/tls/x86_64:/usr/lib64/tls/x86_64:/usr/lib64/tls:/usr/lib64/x86_64/x86_64:/usr/lib64/x86_64:/usr/lib64/x86_64:/usr/lib64            (system search path)
       23579:       trying file=/lib64/tls/x86_64/x86_64/libgcc_s.so.1
       23579:       trying file=/lib64/tls/x86_64/libgcc_s.so.1
       23579:       trying file=/lib64/tls/x86_64/libgcc_s.so.1
       23579:       trying file=/lib64/tls/libgcc_s.so.1
       23579:       trying file=/lib64/x86_64/x86_64/libgcc_s.so.1
       23579:       trying file=/lib64/x86_64/libgcc_s.so.1
       23579:       trying file=/lib64/x86_64/libgcc_s.so.1
       23579:       trying file=/lib64/libgcc_s.so.1
       23579:       trying file=/usr/lib64/tls/x86_64/x86_64/libgcc_s.so.1
       23579:       trying file=/usr/lib64/tls/x86_64/libgcc_s.so.1
       23579:       trying file=/usr/lib64/tls/x86_64/libgcc_s.so.1
       23579:       trying file=/usr/lib64/tls/libgcc_s.so.1
       23579:       trying file=/usr/lib64/x86_64/x86_64/libgcc_s.so.1
       23579:       trying file=/usr/lib64/x86_64/libgcc_s.so.1
       23579:       trying file=/usr/lib64/x86_64/libgcc_s.so.1
       23579:       trying file=/usr/lib64/libgcc_s.so.1
       23579:
  vim: error while loading shared libraries: libgcc_s.so.1: cannot open shared object file: No such file or directory