Creating a Weak Version Definition

Internal changes to an object that do not require the introduction of a new interface definition can be defined by creating a weak version definition. Examples of such changes are bug fixes or performance improvements.

Such a version definition is empty, in that it has no global interface symbols associated with it.

For example, suppose the data file data.c, used in the previous examples, is updated to provide more detailed string definitions:

$ cat data.c
const char * _foo1 = "string used by function foo1()\n";
const char * _foo2 = "string used by function foo2()\n";

A weak version definition can be introduced to identify this change:

$ cat mapfile
SUNW_1.1 {                   # Release X
        global:
                foo1;
        local:
                *;
};

SUNW_1.2 {                   # Release X+1
        global:
                foo2;
} SUNW_1.1;

SUNW_1.2.1 { } SUNW_1.2;     # Release X+2

$ cc -o libfoo.so.1 -M mapfile -G foo.o data.o
$ pvs -dv libfoo.so.1
        libfoo.so.1;
        SUNW_1.1;
        SUNW_1.2:                {SUNW_1.1};
        SUNW_1.2.1 [WEAK]:       {SUNW_1.2};

The empty version definition is signified by the weak label. These weak version definitions enable applications to verify the existence of a particular implementation by binding to the version definition associated with that functionality. The section "Binding to a Version Definition" illustrates how these definitions can be used in more detail.