Since dld allows modules to be added to or removed from an executing process dynamically, some global symbols may not be defined. As a result, an invocation of a function might reference an undefined symbol. We say that a function is executable if and only if all its external references have been fully resolved and all functions that it might call are executable.
dld_function_executable_p helps solve this
problem by tracing the cross references between modules and returns
non-zero only if the named function is executable.
Note that the implementation of dld_function_executable_p is not
complete according to the (recursive) definition of executability.
External references through pointers are not traced. That is,
dld_function_executable_p will still return non-zero if the named
function uses a pointer to indirectly call another function which has
already been unlinked. Furthermore, if one external reference of a
object module is unresolved, all functions defined in this module are
considered unexecutable. Therefore, dld_function_executable_p is
usually too conservative.
However, it is advisable to use dld_function_executable_p to
check if a function is executable before its invocation. In such a
dynamic environment where object modules are being added and removed, a
function that is executable at one point in time might not be executable
at another. Under most circumstances, dld_function_executable_p
is accurate. Also, the implementation of this function has been
optimized and it is relatively cheap to use.
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