DLL Programmer's Guide for TNS/R Systems

Finding Symbol Definitions

DLL Programmer’s Guide for TNS/R Systems—522203-002

4-10

The SearchList for a Globalized Loadfile

below, the programmer of globalized DLL B links it to another globalized library, called

F, that exports the symbol definition of john that B should use. Thus, there appears to

be no ambiguity, and the resolution of john should be simple. But, because B is

globalized, the loader sees it differently.

When loading Program, the loader’s picture is shown in the lower part of Figure 4-5,

which includes DLL B and Lib F as they were linked in the upper part of the figure.

Program requires A, B, and C, and it turns out that john is exported by both A and F.

Recall that imported symbols for every globalized loadfile are resolved using Program’s

globalized searchList, which is Program, UL, A, B, C, H, D, E, F, and G. Because the

loader encounters A’s definition of john before F’s and because B is globalized, the

loader satisfies B’s need with A’s definition, not F’s. If B’s programmer expected

otherwise, there is a surprise in store.

Figure 4-5. Localized and Globalized Symbol Resolution

Program

DLL A

DLL B

DLL C

DLL D

DLL E

Lib G

Lib F

Lib A

Lib B

Lib C

Lib F

Lib D

Lib E

Lib F

Lib G

VST045.vsd

User Library

(DLL)

Lib H

Imports john

Exports john

Program loaded with its required DLLs, including B

DLL B

Lib F

Exports john

DLL B as it was linked.