How do I list the symbols in a so file

Question

How do I list the symbols being exported from a  so file   If possible  I d also like to know their source  e g  if they are pulled in from a static library    I m using gcc 4 0 2  if that makes a difference

User · Accepted Answer

The standard tool for listing symbols is nm, you can use it simply like this:

nm -gD yourLib.so

If you want to see symbols of a C++ library, add the "-C" option which demangle the symbols (it's far more readable demangled).

nm -gDC yourLib.so

If your .so file is in elf format, you have two options:

Either objdump (-C is also useful for demangling C++):

$ objdump -TC libz.so

libz.so:     file format elf64-x86-64

DYNAMIC SYMBOL TABLE:
0000000000002010 l    d  .init  0000000000000000              .init
0000000000000000      DF *UND*  0000000000000000  GLIBC_2.2.5 free
0000000000000000      DF *UND*  0000000000000000  GLIBC_2.2.5 __errno_location
0000000000000000  w   D  *UND*  0000000000000000              _ITM_deregisterTMCloneTable

Or use readelf:

$ readelf -Ws libz.so
Symbol table '.dynsym' contains 112 entries:
   Num:    Value          Size Type    Bind   Vis      Ndx Name
     0: 0000000000000000     0 NOTYPE  LOCAL  DEFAULT  UND
     1: 0000000000002010     0 SECTION LOCAL  DEFAULT   10
     2: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND free@GLIBC_2.2.5 (14)
     3: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND __errno_location@GLIBC_2.2.5 (14)
     4: 0000000000000000     0 NOTYPE  WEAK   DEFAULT  UND _ITM_deregisterTMCloneTable

User · Answer

Try adding -l to the nm flags in order to get the source of each symbol   If the library is compiled with debugging info  gcc -g  this should be the source file and line number   As Konrad said  the object file   static library is probably unknown at this point

User · Answer

nm -g  list the extern variable  which is not necessary exported symbol  Any non-static file scope variable in C  are all extern variable   nm -D  will list the symbol in the dynamic table  which you can find it s address by dlsym   nm --version   GNU nm 2 17 50 0 6-12 el5 20061020

User · Answer

I kept wondering why -fvisibility hidden and  pragma GCC visibility did not seem to have any influence  as all the symbols were always visible with nm - until I found this post that pointed me to readelf and objdump  which made me realize that there seem to actually be two symbol tables    The one you can list with nm The one you can list with readelf and objdump   I think the former contains debugging symbols that can be stripped with strip or the -s switch that you can give to the linker or the install command  And even if nm does not list anything anymore  your exported symbols are still exported because they are in the ELF  dynamic symbol table   which is the latter

User · Answer

If your  so file is in elf format  you can use readelf program to extract symbol information from the binary   This command will give you the symbol table   readelf -Ws  usr lib libexample so   You only should extract those that are defined in this  so file  not in the libraries referenced by it   Seventh column should contain a number in this case   You can extract it by using a simple regex   readelf -Ws  usr lib libstdc   so 6   grep        space         space         6     space        digit         or  as proposed by Caspin    readelf -Ws  usr lib libstdc   so 6   awk   print  8

User · Answer

objdump -TC  usr lib libexample so

User · Answer

If you just want to know if there are symbols present you can use  objdump -h  path to object   or to list the debug info  objdump -g  path to object

User · Answer

You can use the nm -g tool from the binutils toolchain  However  their source is not always readily available  and I m not actually even sure that this information can always be retrieved  Perhaps objcopy reveals further information    EDIT  The tool s name is of course nm  The flag -g is used to show only exported symbols

User · Answer

For shared libraries libNAME so the -D switch was necessary to see symbols in my Linux  nm -D libNAME so   and for static library as reported by others  nm -g libNAME a

User · Answer

For C    so files  the ultimate nm command is nm --demangle --dynamic --defined-only --extern-only  lt my so gt     nm --demangle --dynamic --defined-only --extern-only  usr lib64 libqpid-proton-cpp so   grep work   grep add 0000000000049500 T proton  work queue  add proton  internal  v03  work  0000000000049580 T proton  work queue  add proton  void function0 amp   000000000002e7b0 W proton  work queue  impl  add void proton  internal  v03  work  000000000002b1f0 T proton  container  impl  add work queue   000000000002dc50 T proton  container  impl  container work queue  add proton  internal  v03  work  000000000002db60 T proton  container  impl  connection work queue  add proton  internal  v03  work    source  https   stackoverflow com a 43257338

User · Answer

For Android  so files  the NDK toolchain comes with the required tools mentioned in the other answers  readelf  objdump and nm

[c++] How do I list the symbols in a .so file

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