Tcl Source Code

The attached patch replaces the (confusing, and
incorrect) preprocessor gyrations:

   #ifdef BUILD_sample
   #undef TCL_STORAGE_CLASS
   #define TCL_STORAGE_CLASS DLLEXPORT
   #endif

with the usual Windows idiom, defining a distinct
SAMPLE_STORAGE_CLASS macro instead of hijacking Tcl's
EXTERN macro.

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See also 2025889.

We do need to separate the BUILD_$pkg variants in case one TEA extension depends on another (includes it's .h), which also means we'd need the $pkg_STORAGE_CLASS.  The problem I have with this proposal is that it requires changes on several lines, rather than the single BUILD_$pkg in a .h file that is currently needed.  Can someone convince me this is a better approach?

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The usual convention on Windows is to define a preprocessor
symbol like "XXXAPI", and use declarations like "extern
XXXAPI XXX_Foo(void);", where XXXAPI expands to 
"__declspec(dllexport)" in source modules that are part of
the library and "__declspec(dllimport)" in source modules
that use the library.

This is basically how <tcl.h> defines the EXTERN macro
(which probably should have been called "TCLAPI" instead of
"EXTERN", but that's an historical accident.)

The preprocessor gyrations that Tk and the sampleextension
go through aren't necessarily incorrect, but they are
confusing, error-prone, and unnecessarily complicated.  The
#ifdef / #undef / #define / #include / #undef / #define
cycle is basically hijacking Tcl's storage class macro
"EXTERN" and temporarily repurposing it to mean "My
package's public symbols" instead of "Tcl's public symbols".
 The conventional idiom would be for each extension to
define its own storage class macro instead; that's what the
patch does.

Also, for simple extensions that are only dynamically loaded
and don't export a public, non-stubbed API to dependent
extensions, you don't even need to do that: just declare the
_Init() routine as DLLEXPORT and it will do the right thing
on all platforms.

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What is incorrect about the current incantations?

File Added - 84863: sampleextension-monkey-business.patch