could not read symbols: Archive has no index; run ranlib to add one

i tried making library with

ar -r -c -s libtestlib.a *.o

as given in this tutorial http://matrixprogramming.com/Tools/CompileLink.html

But on linking with library following error comes

g++ -o uni2asc uni2asc.o -L../Modules -ltestlib

../Modules/libtestlib.a: could not read symbols: Archive has no index; run ranlib to add one
collect2: ld returned 1 exit status

i tried with ranlib also but still the error comes.. im working with ubuntu9.10 Please suggest me some solution for this

Solution 1:

Your archive command looks fine, can you try the following. 1) Get the object files in the archive/static library

ar -t libtestlib.a

2) For each object file (say foo.o) from step 1

file foo.o 

This will tell you the format of the object file. If the object file was compiled for a different platform, this would cause a failure to build the index for the archive. To correct this you would need to recompile these files.
3) For each object file from step 1, do

nm foo.o

This will list the symbols exported from the file.

Solution 2:

I was using MinGW to compile a windows app when I got the error, so I found the built-in MinGW commands:

i686-w64-mingw32-ar

And

x86_64-w64-mingw32-ar

Try using those instead of ar if you encounter the problem in MinGW. They both fixed the question's problem for me.

Solution 3:

libtool also has an useful option: -export-symbols-regexp.