| Re: In case someone has trouble including export.h [message #29023] |
Wed, 30 January 2002 05:29  |
Ruediger Kupper
Messages: 7
Registered: February 1999
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Junior Member |
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> Ruediger Kupper wrote:
>
>> Hi!
>>
>> We just ran into a problem with IDL5.5's export.h file, when
>> including it from a c++ source file:
>> I tested g++-2.95 and g++-3.0, and both (most annoyingly)
>> choked on it, due to the following reason:
>>
>> The original export.h shipping with IDL 5.5 featured a prototype
>> declaration with a variable named "template". This choice of name
>> effectively prevents the code from compiling, when included from C++
>> code (even when included 'extern "C" {}').
>
> ...
>
>> The IDL_ARG_PROTO(...) macro is defined near the beginning of the
>> file.
...
>> We could have utilised this by #define-ing
>> IDL_CC_NOT_ANSI, which also seemed to fix the above mentioned problem.
>> But I felt this being much more interfering than simply respelling the
>> name.
James Kuyper wrote:
> ...
>
> The export.h file was apparantly intended to work with C++, as indicated
> by the "#ifdef __cplusplus" lines in it. However, since it contains the
> C++ keyword 'template', used as a variable name, it can't actually be
> compiled in C++.
> Your solution was to compile it by #defining IDL_CC_NOT_ANSI. However,
> that removes the arguments from every function prototype declared using
> the IDL_ARG_PROTO() macro.
>
> In C, that's legal: missing arguments means that the actual number and
> types of the arguments are unspecified. It's up to the programmer to
> make sure that the arguments are of the correct type and number.
>
> However, in C++, if a function declaration contains no arguments, that
> indicates that the function takes no arguments. It's an error to call
> the function with arguments.
Thank you for your expertise in this matter.
As I mentioned, there is a very simple way to solve the
problem, i.e., modifying the export.h file by renaming the
variable called "template" to some arbitrary name (not being
a C++ keyword).
This makes export.h compile fine when included into C++ source.
Concerning the (mis-)use of the IDL_ARG_PROTO() macro, which
I mentioned as a passible alternative, you are of course
perfectly right. This will not work with any compiler
compliant to the C++ standard, and I am sorry, if this
suggestion has led to anyone's confusion.
However, the quick test that a ran, using g++-2.95.4, was
successful and did not yield any compiler errors. This
obviously reflects the fact that g++-2.95.4 was not quite up
to the standard in this issue. Trying to compile it on
g++-3.0.2 led to errors, in the way you suggested it should
happen.
So let me once more apologize, and in summary pin down the
following two conclusions:
o if you want to compile C++ code including IDL5.5's
export.h, you will need to alter the variable name "template"
and
o please use up-to-date compilers.
Regards,
Rüdiger Kupper
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