Re: [netcdfgroup] abi version for netcdf-4.1.2

• To: netcdfgroup@xxxxxxxxxxxxxxxx
• Subject: Re: [netcdfgroup] abi version for netcdf-4.1.2
• From: Andrey Ponomarenko <aponomarenko@xxxxxxxxx>
• Date: Wed, 06 Apr 2011 13:03:10 +0400

On 04/05/2011 09:48 PM, Orion Poplawski wrote:
> My thoughts:
>
> - According to
> http://linuxtesting.org/upstream-tracker/versions/netcdf.html, the
> main ABI problems with going from 4.1.1 -> 4.1.2 was:
>
> ncEnumType.h
> namespace netCDF
> [−] NcEnumType::ncEnumType (5)
>     Change    Effect
> 1    Value of field nc_INT64 has been changed from 8 to 10.   
> Applications may execute another branch of library code.
> 2    Value of field nc_UBYTE has been changed from 5 to 7.   
> Applications may execute another branch of library code.
> 3    Value of field nc_UINT has been changed from 7 to 9.   
> Applications may execute another branch of library code.
> 4    Value of field nc_UINT64 has been changed from 9 to 11.   
> Applications may execute another branch of library code.
> 5    Value of field nc_USHORT has been changed from 6 to 8.   
> Applications may execute another branch of library code.
> [+] affected symbols (1)
> NcGroup::addEnumType ( std::string const& name, NcEnumType::ncEnumType
> basetype ) const:
> 2nd parameter 'basetype' has type 'NcEnumType::ncEnumType'.
>
> Kind of scary when constants change values.
>
> - Adding a new function does not require bumping the soname version
> because that is still backwards compatible.
>
> - Distribution and system maintainers must pay special attention to
> ABI compatibility.  A significant version bump is a good indicator
> that this may happen and to look out for it.  Conversely, "patch"
> level version changes are not expected to have ABI changes.
>

The change of ncEnumType reported by the tool is the false positive.
This is my fault. The issue is that after the clear installation of
netcdf-4.1.1 (./configure --enable-cxx-4, make, make install) there is
no definition for NC_UBYTE, NC_USHORT, NC_UINT and some other constants
in the header files:

4.1.1/include> grep -nR NC_UBYTE .
./ncEnumType.h:24:      nc_UBYTE    = NC_UBYTE, //!< unsigned 1 byte int
./ncType.h:32:      nc_UBYTE    = NC_UBYTE,     //!< unsigned 1 byte int

But the source package of netcdf contains definitions for these constants:

#define    NC_UBYTE     7    /* unsigned 1 byte int */
#define    NC_USHORT     8    /* unsigned 2-byte int */
#define    NC_UINT     9    /* unsigned 4-byte int */
#define    NC_INT64     10    /* signed 8-byte int */
#define    NC_UINT64     11    /* unsigned 8-byte int */
#define    NC_STRING     12    /* string */
#define    NC_VLEN     13    /* used internally for vlen types */
#define    NC_OPAQUE     14    /* used internally for opaque types */
#define    NC_ENUM     15    /* used internally for enum types */
#define    NC_COMPOUND     16    /* used internally for compound types */

I've added these constants to the netcdf.h and rerun the tests [1]. The
CXX4 interface seems to be compatible between 4.1.1 and 4.1.2 and there
is no version bump for this reason:

4.1.1/lib> readelf -Wa libnetcdf_c++4.so.1.0.0|grep SONAME:
 0x0000000e (SONAME)                     Library soname:
[libnetcdf_c++4.so.1]

4.1.2/lib> readelf -Wa libnetcdf_c++4.so.1.0.1|grep SONAME:
 0x0000000e (SONAME)                     Library soname:
[libnetcdf_c++4.so.1]

But there are two changed constants in C interface: NC_WRITE (from 0x1
to 0x0001) and NC_NOCLOBBER (from 0x4 to 0x0004) used by ncopen and
nccreate functions. So, the soname has been bumped:

4.1.1/lib> readelf -Wa libnetcdf.so.4.0.0|grep SONAME
 0x0000000e (SONAME)                     Library soname: [libnetcdf.so.4]

4.1.2/lib> readelf -Wa libnetcdf.so.7.0.1|grep SONAME
 0x0000000e (SONAME)                     Library soname: [libnetcdf.so.7]


[1] Test results for libnetcdf
<http://linuxtesting.org/upstream-tracker/versions/netcdf.html>

-- 
Andrey Ponomarenko
Department for Operating Systems at ISPRAS
 web:    http://www.LinuxTesting.org
 mail:   aponomarenko@xxxxxxxxx

• References:
  • [netcdfgroup] abi version for netcdf-4.1.2
    • From: marco atzeri
  • Re: [netcdfgroup] abi version for netcdf-4.1.2
    • From: Ed Hartnett
  • Re: [netcdfgroup] abi version for netcdf-4.1.2
    • From: Orion Poplawski