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Article #16599: third party DLL funcs with no underscore

 Question and Answer Database

FAQ1599C.txt   third party DLL funcs with no underscore
Category   :Linker
Platform    :All
Product    :C++Builder  1.x

Question:

Q: Why does BCB give me underscores on references to
functions in a DLL that don't have underscores? Then 
I get undefined symbols when linking.

Answer:


A: Microsoft handles the cdecl ( __cdecl ) calling convention
differently than Borland does in that they do not prepend 
underscores. There are a couple of possible resolutions like:

(a) turning off "generate underscores" 
(Options | Compiler | Compiler output) will cause the
compiler to cease prepending underscors, but then calls
into the run-time library will have to be modified to 
have an explicit underscore. This can be accomplished 
during pre-processing:
#define sprintf  _sprintf
#define strlen   _strlen

(b) using aliases in the IMPORTS section of the DEF file 
for the executable.

IMPORTS
_SQLDebug = NTWDBLIB.SQLDebug


To get the symbols exactly as they are exported run
IMPDEF on the DLL. Copy and paste these exported
symbols into thr IMPORTS section of your executable's 
DEF file, adding the DLL name and the alias. Then 
link with your DEF file in place of the import library.

For more information on this technique, consult the
chapter on module definition files in Petzold's
Programming Windows 3.1 book.


7/2/98 10:32:32 AM
 

Last Modified: 01-SEP-99