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typedef'd struct ptr as argument (C)

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Started by discman1028 March 04, 2007 07:37 AM

10 comments, last by Alpha_ProgDes 17 years, 1 month ago

discman1028

212

Author

March 04, 2007 07:37 AM

The following declaration of LogMatrix4DContents() gives errors...


typedef struct
{
	// Column-major matrix.
	float32	_11,
			_21,
			_31,
			_41,

			_12,
			_22,
			_32,
			_42,

			_13,
			_23,
			_33,
			_43,

			_14,
			_24,
			_34,
			_44;
} Matrix4f;

void LogMatrix4DContents( Matrix4f* pMat ); // Gives errors...

error C2143: syntax error : missing ')' before '*'
error C2143: syntax error : missing '{' before '*'
error C2059: syntax error : ')'

So I end up having to do this for now:


void LogMatrix4DContents( void* pMat );

...

void LogMatrix4DContents( void* pMat )
{
	Matrix4f* pM = (Matrix4f*)(pMat);

	...
}

Any idea? VS2005Pro, compiling in C. Though, had the same problem in old Turbo C. Note that 'LogVector4DContents()' worked fine, which is exactly analogous.. Maybe I'm forgetting something fundamental about C.

--== discman1028 ==--

Alpha_ProgDes

6,963

March 04, 2007 08:21 AM

I used Dev-C++'s C compiler and this worked:

#include <stdio.h>#include <stdlib.h>typedef float float32;typedef struct{	 // Column-major matrix.	 float32	_11,			_21,			_31,			_41,			_12,			_22,			_32,			_42,			_13,			_23,			_33,			_43,			_14,			_24,			_34,			_44;} Matrix4f;void LogMatrix4DContents( Matrix4f* pMat ); // Gives errors...int main(int argc, char *argv[]){    system("PAUSE");	  return 0;}

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ToohrVyk

1,596

March 04, 2007 08:22 AM

Very strange: gcc has no trouble compiling the following:

typedef float float32;typedef struct{	// Column-major matrix.	float32	_11,			_21,			_31,			_41,			_12,			_22,			_32,			_42,			_13,			_23,			_33,			_43,			_14,			_24,			_34,			_44;} Matrix4f;void LogMatrix4DContents( Matrix4f* pMat );

It would seem as if you had code before the function definition that you didn't post and contains a syntax error, which cascades into the function definition.

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Alpha_ProgDes

6,963

March 04, 2007 08:42 AM

One thing to note: ToohrVyk and I have float32 defined whereas your code doesn't. When I tried your code the first time, I got the same errors you did. After I added the typedef for float32, then the code compiled without issue.

So are you sure that float32 is actually defined in your code somewhere?

Beginner in Game Development? Read here. And read here.

discman1028

212

Author

March 04, 2007 11:07 AM

Yeh, in fact I really gave no context. The typedef is in Matrix.h, the func declaration is in Util.h, and the definition is in Util.c. I used Matrix4f everywhere for a long time, with no problems, until trying this. Probably a Matrix.h or Matrix4f naming conflict I didn't see coming...

My complete Util.h:

#ifndef _UTIL_H_#define _UTIL_H_#include "Types.h" // Defines float32#include "Matrix.h" // Defines Matrix4f#include "Vector.h" // Defines Vector4f#include <math.h>...void InitLog( char8* sFilename );void Log( char8* sString );void LogVector4DContents( Vector4f* pVect );void LogMatrix4DContents( Matrix4f* pMat ); // ERROR!void CloseLog();#endif

--== discman1028 ==--

Alpha_ProgDes

6,963

March 04, 2007 11:13 AM

Does Matrix.h include Types.h?

//Matrix.h#include "Types.h" //I won't lie.                    //I don't know if this goes outside or inside the ifndef/define#ifndef blah#define blah//Matrix code#endif

Also try to see if this bit of your code still works as of right now:
void LogVector4DContents( Vector4f* pVect );

Beginner in Game Development? Read here. And read here.

LessBread

1,415

March 04, 2007 12:09 PM

Try it like this

typedef float float32;typedef struct tagMatrix4f { // NOTE THE ACTUAL NAME OF THE STRUCT IS HERE	 // Column-major matrix.	 float32	_11,			_21,			_31,			_41,			_12,			_22,			_32,			_42,			_13,			_23,			_33,			_43,			_14,			_24,			_34,			_44;} Matrix4f; // HERE IS AN ALIAS

"I thought what I'd do was, I'd pretend I was one of those deaf-mutes." - the Laughing Man

Alpha_ProgDes

6,963

March 04, 2007 12:14 PM

@Lessbread: what's the difference?

Beginner in Game Development? Read here. And read here.

LessBread

1,415

March 04, 2007 12:56 PM

In my experience with C, when typedefing a struct, giving it a tagname as well as an eventual typename just works best. It seems to me that with

typedef struct tag
{
...
} T;

T operates as a stand in for "struct tag". So that when the tag is omitted

typedef struct
{
...
} T;

T operates as a stand in for ... nothing. So there's no using T* as a function argument because the compiler has troubles determining what T* points to.

Maybe someone else will come along quoting the spec and contradict all that - just because "operate" wasn't the correct verb to use but like I wrote, in my experience when typedefing a struct it just works better when it's given a tag.

This might explain it: Tag vs. Type Names

Quote:
But C treats tags differently than it does other identifiers. C compilers hold tags in a symbol table that's conceptually, if not physically, separate from the table that holds all other identifiers. Thus, it's possible for a C program to have both a tag and an another identifier with the same spelling in the same scope.

"I thought what I'd do was, I'd pretend I was one of those deaf-mutes." - the Laughing Man

discman1028

212

Author

March 04, 2007 03:36 PM

Y'know, intuitively I've always felt the same way, that leaving out the tag is bad. Since then, you're typedef'ing to this big thing instead of just to the tag. But I'm pretty sure it just generates a garbage tag anyways.

In any case, adding a tag didn't help. (Neither did changing the function to LogMatrix4DContents( struct mytag* pMat )).

It doesn't matter at this point, but I'll send the project in a bit if anyon'es interested. It's a real mystery.

EDIT: I take that back! LogMatrix4DContents( struct mytag* pMat ) did work! What the hell... why does LogVector4DContents( Vector4f* pVect ) work then?

--== discman1028 ==--

typedef'd struct ptr as argument (C)

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