Function Question

[Bryan Parkoff]

Do C/C++ Compiler allow function to contain more than 8 parameters? I
checked MS Visual C++ 6.0 that it can only limit 8 parameters, but
most C/C++ Compiler can limit maximum 256 parameters. Can you please
verify for me?
Usually, I write function that is about 100 lines. I would need
20 parameters which they are all reference to global variable inside
struct. For best optimization, it does not require to create stack
frame because variables are always global inside struct. It is
possible that stack frame is never created because local variables are
never defined.
I like pointer to function into array that it looks like CALL
Table, but I prefer to use switch cases that it looks like JMP Table
because all functions under pointer list can't be inlined or
forceinlined, but only sub-functions can be inlined or forceinlined
inside pointer to function list.
Are you sure that pointer to function list can only limit to 1,023
while switch cases can limit to 300 or 1,023 for best optimization?
I have another problem with #define, #undef, and #ifdef directive
inside functions. I have three duplicated functions with 10 lines.
First function has 8 lines, Second function has 9 lines. Third
function has 10 lines. I prefer to use only one function so #ifdef
name and #endif will be placed on line 9 and line 10.
Most functions can have #define and #undef before it starts to
call function with 10 lines. If #undef is executed, 9th line and/or
10th line will be ignored. I tried to test, but it seems not working.
It accepts to execute 9th line and 10th line while #undef is
executed. I don't know why.
Do I have to accept the fact that I can't use #define and #undef
inside most functions before it calls function with 10 lines? Then, I
am advised to create 3 duplicated functions -- 8 lines, 9 lines, and
10 lines. Most functions will have pointer to function that can
choose to point one of three duplicated functions. The problem is
that I want 3 functions to be forceinlined for best performance
because pointer to function does not allow. If I try, I will get
error message saying, inline or forceinlined must be removed before it
is compiled.
Please advise what I have to do other option.

 

[George]

Please advise? how about "get a job" troll-****....

 

[lallous]

Hello Bryan,

Do C/C++ Compiler allow function to contain more than 8 parameters? I
checked MS Visual C++ 6.0 that it can only limit 8 parameters, but
most C/C++ Compiler can limit maximum 256 parameters. Can you please
verify for me?
Usually, I write function that is about 100 lines. I would need
20 parameters which they are all reference to global variable inside
struct. For best optimization, it does not require to create stack
frame because variables are always global inside struct. It is
possible that stack frame is never created because local variables are
never defined.
I like pointer to function into array that it looks like CALL
Table, but I prefer to use switch cases that it looks like JMP Table
because all functions under pointer list can't be inlined or
forceinlined, but only sub-functions can be inlined or forceinlined
inside pointer to function list.
Are you sure that pointer to function list can only limit to 1,023
while switch cases can limit to 300 or 1,023 for best optimization?

I don't think the standard should be dictating any limit on how much a
function can take as max parameters.

VC++ 6, for sure, allows more than 8 params.

I have another problem with #define, #undef, and #ifdef directive
inside functions. I have three duplicated functions with 10 lines.
First function has 8 lines, Second function has 9 lines. Third
function has 10 lines. I prefer to use only one function so #ifdef
name and #endif will be placed on line 9 and line 10.
Most functions can have #define and #undef before it starts to
call function with 10 lines. If #undef is executed, 9th line and/or
10th line will be ignored. I tried to test, but it seems not working.
It accepts to execute 9th line and 10th line while #undef is
executed. I don't know why.

I don't know if you know that #ifdef/#undef will only allow a certain part
of the code to be compiled while the code that didn't fulfill your condition
won't exist at all. Unlike "if/else" which are runtime checks.

If you still want to write one function, just add an extra parameter to your
function as:
int threeinon(int x, int y, int whatfunction)

then inside this function check for 'whatfunction' value and see if you need
to execute a certain addition code.

you may want to use "structs and unions" to build a struct that can be
passed as a param to "threeinon" so that each version of that function can
have its own set of parameters.

Do I have to accept the fact that I can't use #define and #undef
inside most functions before it calls function with 10 lines? Then, I
am advised to create 3 duplicated functions -- 8 lines, 9 lines, and
10 lines.

How you mean, it...Show some code please.

Most functions will have pointer to function that can
choose to point one of three duplicated functions. The problem is
that I want 3 functions to be forceinlined for best performance
because pointer to function does not allow. If I try, I will get
error message saying, inline or forceinlined must be removed before it
is compiled.
Please advise what I have to do other option.

If you're using VC++ and its features (which might not apply to other
compilers) then it is advised to repost your question to appropriate
newsgroup.

This list targets platform independent C++ issues.

Regards,
Elias

 

[Thomas Matthews]

Do C/C++ Compiler allow function to contain more than 8 parameters? I
checked MS Visual C++ 6.0 that it can only limit 8 parameters, but
most C/C++ Compiler can limit maximum 256 parameters. Can you please
verify for me?
Usually, I write function that is about 100 lines. I would need
20 parameters which they are all reference to global variable inside
struct. For best optimization, it does not require to create stack
frame because variables are always global inside struct. It is
possible that stack frame is never created because local variables are
never defined.

The common practice is to place many parameters for a function into
a structure, then pass the structure. A function that has more than
5 parameters becomes unreadable.

I like pointer to function into array that it looks like CALL
Table, but I prefer to use switch cases that it looks like JMP Table
because all functions under pointer list can't be inlined or
forceinlined, but only sub-functions can be inlined or forceinlined
inside pointer to function list.
Are you sure that pointer to function list can only limit to 1,023
while switch cases can limit to 300 or 1,023 for best optimization?

A table of function pointers is only limited by the memory of your
machine or some compiler limit.

I agree with what other people have stated in your first post: if
you have that many selections, you design needs to be reviewed.

I have another problem with #define, #undef, and #ifdef directive
inside functions. I have three duplicated functions with 10 lines.
First function has 8 lines, Second function has 9 lines. Third
function has 10 lines. I prefer to use only one function so #ifdef
name and #endif will be placed on line 9 and line 10.
Most functions can have #define and #undef before it starts to
call function with 10 lines. If #undef is executed, 9th line and/or
10th line will be ignored. I tried to test, but it seems not working.
It accepts to execute 9th line and 10th line while #undef is
executed. I don't know why.

Sounds ugly. Here are some suggestions:
1. Have a function that contains the common 8 lines.
Have two functions that first call the 8 line function then perform
their next lines.

2. Consider using a Function Object or Functor. Place the 8 lines
into a base class for the Functor. Create descendant functor
classes that contain the additional code.

Do I have to accept the fact that I can't use #define and #undef
inside most functions before it calls function with 10 lines? Then, I
am advised to create 3 duplicated functions -- 8 lines, 9 lines, and
10 lines. Most functions will have pointer to function that can
choose to point one of three duplicated functions. The problem is
that I want 3 functions to be forceinlined for best performance
because pointer to function does not allow. If I try, I will get
error message saying, inline or forceinlined must be removed before it
is compiled.
Please advise what I have to do other option.

Show your code and indicate what you want the code to perform.


--
Thomas Matthews

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