Re: How can I detect the compiler version used to generate a .a or .so library

[Dirk Hoffmann]

On Tue, 14 Feb 2006, Gelu Ionescu wrote:

> How can I detect the compiler version used to generate a .a or .so library?

Hi Gelu,

As far as I know, the GNU compilers don't interlace a compiler stamp or 
similar into the output code. Precisely speaking, a library is 
generated by a linker, not a compiler; you can in principle build a 
library from object files which have in turn been compiled with 
different compiler versions. 

If you compile the sources yourself, you may include something like
        static char _gcc_vers[] = __VERSION__;
in your sourcefiles (or otherwise hope the author did), which you can 
extract by "strings mylib.so" for example (along with many unwanted 
"junk", so have a good eye or filter).

However, since gcc/g++ v3.X (and the corresponding linker!), the ABI permits
per some insight into the genesis of compiled code by default, as long as
symbols are not stripped from the binaries. Try:

 nm -C mylib.so | grep @@GLIB | sed 's/^.*@@//' | sort -u

The output (if above conditions are fulfilled) will look like this:

 GLIBC_2.0
 GLIBC_2.1
 GLIBC_2.1.3
 GLIBC_2.2
 GLIBC_2.3
 GLIBCPP_3.2
 GLIBCPP_3.2.2

(Change the grep argument, if only g++ output wanted, but be aware that the
acronym changed later for GLIBCXX, as "CPP" was already in use as a tag for
the preprocessor.)

The output means the following: The most recent (in terms of compiler used)
function calls in mylib.so go to a function/binary/library, which has been
compiled with gcc v2.3 or g++ v3.2.2 respectively. This gives you a _lower_
limit on the version of the compiler which was used to generate the code
which calls the function. In most cases, this should however be what you
want to know. ("Is my library compatible or more recent than the compiler I
want to use to put my program together?") Details on the ABI are available
at: http://gcc.gnu.org/onlinedocs/libstdc++/abi.html



PS: This reasoning can be bowled down, if you can not assume "linear"  
compiler installation/evolution on your platform, i.e. that some one linked
a newer library with an older compiler, which may entail a lot of other
problems then anyway.