How to get GNAT version during build process

[Jerry]

How would one discover the version of GNAT used in a build? I'm
inquiring for someone using cmake. They have cobbled something
together but I get the feeling it is too brittle and requires manual
updating from time to time. Here is the patch that someone submitted:


diff -up plplot-5.9.9/cmake/modules/ada.cmake.gnat plplot-5.9.9/cmake/
modules/ada.cmake
--- plplot-5.9.9/cmake/modules/ada.cmake.gnat 2011-10-12
18:43:01.000000000 -0600
+++ plplot-5.9.9/cmake/modules/ada.cmake 2012-01-04 08:58:11.501470982
-0700
@@ -43,7 +43,7 @@ if(ENABLE_ada)
endif(ENABLE_ada)

if(ENABLE_ada)
- find_library(GNAT_LIB NAMES gnat gnat-4.5 gnat-4.4 gnat-4.3
gnat-4.2 gnat-4.1)
+ find_library(GNAT_LIB NAMES gnat gnat-4.7 gnat-4.6 gnat-4.5
gnat-4.4 gnat-4.3 gnat-4.2 gnat-4.1)
if(NOT GNAT_LIB)
message(STATUS "WARNING: "
"gnat library not found. Disabling ada bindings")


I stumbled across
GNAT.Compiler_Version (g-comver.ads)
in the GNAT library but when I ran this

with Ada.Text_IO; use Ada.Text_IO;
with GNAT.Compiler_Version;
procedure ada_version is
package CVer is new GNAT.Compiler_Version;
use Cver;
begin
Put_Line(Version);
end ada_version;

all I got was this

GPL 2010 (20100603)

whereas g-comver.ads promises a result in this format

v.vvx (yyyyddmm)"

where v.vv would be something like 3.16.

Jerry

[Simon Wright]

You would have thought that cmake's find_library() would have found
libgnat; here, GNAT GPL 2011 gives (in
lib/gcc/x86_64-apple-darwin10.2.0/4.5.3/adalib)

$ ls -l libgnat*
-rwxr-xr-x@ 1 simon simon 3886280 19 Apr 2011 libgnat-2011.dylib
-rw-r--r--@ 1 simon simon 5321016 19 Apr 2011 libgnat.a
lrwxr-xr-x@ 1 simon simon 18 19 Apr 2011 libgnat.dylib -> libgnat-2011.dylib

Perhaps it doesn't like symlinks.

The comment in g-comver.ads is wrong even with 4.6.0: it just returns
"4.6.0".

I suppose we could continue the fragility by adding gnat-2010 gnat-2011
etc to the proposed patch!