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Q49008: /NOI Switch May Cause L2022 and L2029 in PM Programs

Article: Q49008
Product(s): See article
Version(s): 5.10   | 5.10
Operating System(s): MS-DOS | OS/2
Keyword(s): ENDUSER | | mspl13_basic
Last Modified: 27-OCT-1989

I am compiling and linking a Presentation Manager (PM) program from
Charles Petzold's "Programming the OS/2 Presentation Manager" and I
get the following link errors:

   LINK : error L2022: ClientWndProc (alias ClientWndProc) : export
          undefined

        : error L2029 : 'ClientWndProc' : unresolved external

I get the same errors when compiling WELCOME1.C from the companion
disk to "Programming the OS/2 Presentation Manager."

The /NOI switch instructs the linker to preserve case. If you are
using the /NOI switch, the linker will generate these errors because
EXPENTRY (the export entry point) is defined in OS2DEF.H as follows:

   #define EXPENTRY far pascal

The "pascal" keyword instructs the compiler to use the left-to-right
calling sequence for the functions that it modifies. The keyword also
causes the conversion of the function's name to uppercase letters.

All window procedures are defined as EXPENTRY. Thus, the name of your
window procedure is converted to uppercase letters. In your .DEF, you
export your window procedures as follows:

   EXPORTS         ClientWndProc

Because of the /NOI switch, the linker does not view ClientWndProc and
CLIENTWNDPROC as being equal. Consequently, you get the first error
message "export undefined."

The second error message is generated because ClientWndProc (mixed
uppercase and lowercase letters) is not recognized as being defined,
so the linker considers it an "unresolved external."

Removing the /NOI switch from your link line corrects both errors.

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