I am in VS2003, building C++ .dll libraries.

I want to create a single .dll that combines its own code with code from
other dlls. For example, I want to build B.dll, where B has its own source
code, and also refers to routines in A.dll. I have another app C.exe that
will link to B.dll (and/or A.dll).

Clearly there is a dependency: B depends on A.

I can build and link A.dll  just fine on its own. But when I try to build
B.dll, I get problems.

The first problem was that when I tried to build B.dll on its own, the
routines in A that B wants were not there, so I got a slew of LNK2001 and
LNK2019 (unresolved external symbol) errors, for all the routines in A that
are referred to in B.

My attempt to fix this was to set A.dll as input to the linker in B, in
Additional Dependencies. However, when I do this, it fails with LNK1136
(invalid or corrupt file), presumably because I am linking in a .dll, not a
.lib

There is no A.lib, and I don't know where else the linker for B can find the
routines in A that it needs.

What can I do to fix this?

Thanks