Re: DllMain implementation

From:

"Ben Voigt [C++ MVP]" <rbv@nospam.nospam>

Newsgroups:

microsoft.public.vc.language

Date:

Tue, 12 Feb 2008 13:11:55 -0600

Message-ID:

<OVcw7rabIHA.1132@TK2MSFTNGP06.phx.gbl>

George wrote:

Hi Ben,

I know some compilers have the concept of a "weak" symbol, where the
duplicate definition warning is skipped.

Does the above rule you mentioned applies to my question? If yes, any
more descriptions how it applies please?

Visual C++ is not one of the compilers which designate symbols as weak or
strong, so this probably doesn't interest you. In other compilers, the
"weak" symbol marking is used to allow a library to provide a default
implementation of a symbol which the user can override by providing his own.

regards,
George

"Ben Voigt [C++ MVP]" wrote:

George wrote:

Thanks Will,

So you think the sequence of input object file matters? i.e. user
defined DllMain is always provided before default one?

Any if user provides one, there is no duplicated define symbol
errors?

I know some compilers have the concept of a "weak" symbol, where the
duplicate definition warning is skipped.

regards,
George

"William DePalo [MVP VC++]" wrote:

"George" <George@discussions.microsoft.com> wrote in message
news:5CA28152-9BE7-45A4-8F67-20DA96A6A307@microsoft.com...

CRT is implemented a way that if developer provides DllMain, it
will use the
provided one, or else the default DllMain is used.

I am wondering how to implement similar selective linking
approach? i.e. if
there are more than one implementations of a method of the same
signature, I
can control which one has the higher priority to link, and if the
highest priority one does not exist, the second priority one will
be used (and compiler will have no duplicated method
warning/error).

Here is what I'm sure of: The CRT has a source file named
Dllmain.c. The comments say it is used when no other version is
provided.

Here is what I'm not sure of: I think that it is a simple matter
specifying Dllmain.obj on the linker command line but _after_ all
of the other object modules and libraries. If the reference is
resolved early, the CRT's Dllmain won't be linked. If not, it will

Regards,
Will