[SOLVED] How to determine if a .a file is 32 bit or 64 bit?

Tinyspark · 05-24-2012, 01:48 AM

Hi,
I have a file "liberm.a". Is there a command to determine whether this .a file is compatible with 32 bit or 64 bit compiler?

catkin · 05-24-2012, 01:58 AM

Try the file command

Tinyspark · 05-24-2012, 02:16 AM

Hi CatKin,
file command gives me the following output.

[root@dyl02703app004 lib]# file liberm.a
liberm.a: current ar archive

pan64 · 05-24-2012, 02:25 AM

probably it means the liberm.a is compatible with the current system (so if you have a 32bit system this lib is 32bit too).
you can also try ar to unpack archive and execute file on <something>.o

Tinyspark · 05-24-2012, 02:32 AM

Hi pan64,
but when I run a makefile which uses liberm.a, I get an error that it is incompatible.
Please find the error below: (here, -lerm refers to liberm.a)

/usr/bin/ld: skipping incompatible /home/wholesale/children/dev5/lib/liberm.a when searching for -lerm
/usr/bin/ld: cannot find -lerm

pan64 · 05-24-2012, 02:38 AM

so in this case it is incompatible with the files you are actually trying to link - I do not see the command line. So you can try also to write a dummy main and link this lib also you can change arch by: -m32 or -m64.

colucix · 05-24-2012, 02:41 AM

The .a files are only archives. You have to query the object files inside them to retrieve this information:

Code:

objdump -f liberm.a | grep "file format"

and you will retrieve either elf64-x86-64 or elf32-i386.

Tinyspark · 05-24-2012, 02:55 AM

Hi colucix, what exactly do you mean by "file format" ?

pan64 · 05-24-2012, 02:57 AM

Quote:

Originally Posted by Tinyspark

Hi colucix, what exactly do you mean by "file format" ?

that is what you asked. Is this a 32bit or 64bit code?
On some platform file reports it correctly (and there is no objdump), on some other platform you can try objdump or that dummy main.c to test it.

Tinyspark · 05-24-2012, 03:13 AM

Thanks colucix and pan64.
objdump command has given me the required output.

colucix · 05-24-2012, 03:22 AM

Quote:

Originally Posted by Tinyspark

Hi colucix, what exactly do you mean by "file format" ?

It is only a string in the output of objdump, which refers to the architecture of the object files, as pan64 already pointed out. Look at the entire output of objdump (whitout piping to grep) to have a clearer picture of the whole thing.