External C function and duplicate symbol
Hi guys, I've few functions that I'm keeping on an external .h file.
If the header is included in more than a class I get duplicate symbol
error. I tried using #ifndef which I use on my C++ classes but didn't
bring any luck. I had a look to the various headers in the framework
and I saw they use the following sintax:
#define VEC_ZERO_2(a) \
{ \
(a)[0] = (a)[1] = 0.0; \
}
Isn't there a way to achieve the same but having parameters and returns typed?
Thanks, chr
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Re: External C function and duplicate symbol
What about using #pragma once at the top of the header file? The other
solution is to move the functions to a C file and move just the
function definitions to header files. I prefer the second for
readability. I usually have a utils.c and a utils.h. I'm not a big fan
of function implementations in header files.
Scott
On Oct 3, 2008, at 4:19 AM, Christian Giordano wrote:
Hi guys, I've few functions that I'm keeping on an external .h file.
If the header is included in more than a class I get duplicate symbol
error. I tried using #ifndef which I use on my C++ classes but didn't
bring any luck. I had a look to the various headers in the framework
and I saw they use the following sintax:
#define VEC_ZERO_2(a) \
{ \
(a)[0] = (a)[1] = 0.0;\
}
Isn't there a way to achieve the same but having parameters and
returns typed?
Thanks, chr
___
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Re: External C function and duplicate symbol
It seems that what you want is an inline C function. I don't think
this is part of the C language standard but gcc seems to have its own
method of doing this. Just do a find on 'inline' in the Frameworks to
see how it's done. Look at CGBase.h for instance.
On Oct 3, 2008, at 8:32 AM, Scott Andrew wrote:
What about using #pragma once at the top of the header file? The
other solution is to move the functions to a C file and move just
the function definitions to header files. I prefer the second for
readability. I usually have a utils.c and a utils.h. I'm not a big
fan of function implementations in header files.
Scott
On Oct 3, 2008, at 4:19 AM, Christian Giordano wrote:
Hi guys, I've few functions that I'm keeping on an external .h file.
If the header is included in more than a class I get duplicate symbol
error. I tried using #ifndef which I use on my C++ classes but didn't
bring any luck. I had a look to the various headers in the framework
and I saw they use the following sintax:
#define VEC_ZERO_2(a) \
{ \
(a)[0] = (a)[1] = 0.0; \
}
Isn't there a way to achieve the same but having parameters and
returns typed?
___
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Re: External C function and duplicate symbol
Hi Christian
If you really want a function to appear in multiple object files
you could declare them static, like in:
static void vec_zero2(int *vect)
{
vec[0] = vec[1] = 0;
}
This is sometimes useful if you want to inline small functions
and not use preprocessor macros like this:
static inline char *code_long(char *dst, u_int32_t in)
{
dst[0] = (in 24) 0xff; // '' for readability only
dst[1] = (in 16) 0xff;
dst[2] = (in 8) 0xff;
dst[3] = (in 0) 0xff; // '' for readability only
return dst;
}
This works also mixing C and Obj-C:
static void callSomething(id myObject, int x, y)
{
[myObject withX:x andY:y];
[myObject setTitle:[NSString stringWithFormat:@Position: %d,%d, x,
y]];
}
Of course this will increase your code size if you are not considering
the size of your static functions. 'otool' or the assembler listing
within
XCode is useful to look at the generated code.
Everything else should be declared 'extern' and implemented in one
source file only. That's only my opinion, of course.
Regards,
Patrick
On 03.10.2008, at 13:19, Christian Giordano wrote:
Hi guys, I've few functions that I'm keeping on an external .h file.
If the header is included in more than a class I get duplicate symbol
error. I tried using #ifndef which I use on my C++ classes but didn't
bring any luck. I had a look to the various headers in the framework
and I saw they use the following sintax:
#define VEC_ZERO_2(a) \
{ \
(a)[0] = (a)[1] = 0.0;\
}
Isn't there a way to achieve the same but having parameters and
returns typed?
Thanks, chr
___
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