how to write a wrapper function?

F

franco ziade

I am stuck :(
I am trying to pass the address of a function as an argument to a function
(some OS call to launch a task):

Example:
--------
Declaration of the OS "lunch a Task"
LunchTask(..., * void functionAddress(void), ....)

The function address needs to be passed here, let's say the following

void MyTask::TaskFunction(void);

The compiler refuses it with the error, expecting *void (void) cannot pass
void MyTask::* (void).
I tried to cast but It doesnt accept it :(

I was told i could write a C wrapper function -
Can someone help out on how a wrapper function is used? where is it defined?
how does it pass the C++ function address?

Thanks
 
B

Ben Pfaff

franco ziade said:
void MyTask::TaskFunction(void);

Your question is outside the domain of comp.lang.c, which discusses
only the standard C programming language, including the standard C
library. This is a remarkably narrow topic compared to what many
people expect.

For your convenience, the list below contains topics that are not
on-topic for comp.lang.c, and suggests newsgroups for you to explore
if you have questions about these topics. Please do observe proper
netiquette before posting to any of these newsgroups. In particular,
you should read the group's charter and FAQ, if any (FAQs are
available from www.faqs.org and other sources). If those fail to
answer your question then you should browse through at least two weeks
of recent articles to make sure that your question has not already
been answered.

* OS-specific questions, such as how to clear the screen,
access the network, list the files in a directory, or read
"piped" output from a subprocess. These questions should be
directed to OS-specific newsgroups, such as
comp.os.ms-windows.programmer.misc, comp.unix.programmer, or
comp.os.linux.development.apps.

* Compiler-specific questions, such as installation issues and
locations of header files. Ask about these in
compiler-specific newsgroups, such as gnu.gcc.help or
comp.os.ms-windows.programmer.misc. Questions about writing
compilers are appropriate in comp.compilers.

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assembly and machine code. x86 questions are appropriate in
comp.lang.asm.x86, embedded system processor questions may
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* Making C interoperate with other languages. C has no
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* The C standard, as opposed to standard C. Questions about
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* C++. Please do not post or cross-post questions about C++
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* Test posts. Please test in a newsgroup meant for testing,
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news.groups.questions is a good place to ask about the appropriate
newsgroup for a given topic.
 
E

E. Robert Tisdale

franco said:
I am stuck :(
I am trying to pass the address of a function as an argument to a function
(some OS call to launch a task):

Example:
LunchTask(..., * void functionAddress(void), ....)

The function address needs to be passed here, let's say the following

void MyTask::TaskFunction(void);

MyTask t; // global object
extern "C" {
void taskFunction(void) {
t.TaskFunction();
}
}
The compiler refuses it with the error,
expecting *void (void) cannot pass void MyTask::* (void).
I tried to cast but It doesnt accept it :(

I was told [that] I could write a C wrapper function -
Can someone help out on how a wrapper function is used?
Where is it defined?
How does it pass the C++ function address?
 
M

Michael Mair

franco said:
I am stuck :(
I am trying to pass the address of a function as an argument to a function
(some OS call to launch a task):

Example:

Your OS must be very hospitable.
LunchTask(..., * void functionAddress(void), ....)

A pointer to a function with empty argument list and no returns
looks like that:
void (*functionAddress)(void)
The function address needs to be passed here, let's say the following

void MyTask::TaskFunction(void);

The compiler refuses it with the error, expecting *void (void) cannot pass
void MyTask::* (void).
I tried to cast but It doesnt accept it :(

This is C++. However, try it with function pointers and not some
guess of how they might look. BTW: In C, you do not have to use the
address operator on the function to get its address.

void foo (void);

......
functionAddress = foo;
I was told i could write a C wrapper function -
Can someone help out on how a wrapper function is used? where is it defined?
how does it pass the C++ function address?

Try the above and go on to comp.lang.c++ if it does not work.


Cheers
Michael
 

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