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* [Bug c/49182] New: Fordward declarations of struct not usable in function pointer types.
@ 2011-05-26 23:10 brad.lionberger at intel dot com
2011-05-26 23:12 ` [Bug c/49182] " pinskia at gcc dot gnu.org
` (5 more replies)
0 siblings, 6 replies; 7+ messages in thread
From: brad.lionberger at intel dot com @ 2011-05-26 23:10 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49182
Summary: Fordward declarations of struct not usable in function
pointer types.
Product: gcc
Version: 4.5.2
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: brad.lionberger@intel.com
A forward declaration of a struct to be used in a function pointer type
definition confuses the compiler. The following code does not compile using
gcc but will with two other compilers.
// Forward declaration
typedef struct _a a;
// Pointer to function with struct as parameter
typedef int (*FxnPointer)(a* WontComplie);
// Actual declaration of struct with function pointer type declared above.
typedef struct _a
{
int foo;
int bar;
FxnPointer PtrToFxn;
} a;
int main(void)
{
a test_struct;
return 0;
}
Errors returned are as follows:
FxnPtrEx.c:13:3: error: redefinition of typedef ‘a’
FxnPtrEx.c:2:19: note: previous declaration of ‘a’ was here
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c/49182] Fordward declarations of struct not usable in function pointer types.
2011-05-26 23:10 [Bug c/49182] New: Fordward declarations of struct not usable in function pointer types brad.lionberger at intel dot com
@ 2011-05-26 23:12 ` pinskia at gcc dot gnu.org
2011-05-26 23:23 ` pinskia at gcc dot gnu.org
` (4 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: pinskia at gcc dot gnu.org @ 2011-05-26 23:12 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49182
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution| |INVALID
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> 2011-05-26 23:10:11 UTC ---
This is invalid C but valid C++. GCC is correct as typedef for the same type
is invalid for C.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c/49182] Fordward declarations of struct not usable in function pointer types.
2011-05-26 23:10 [Bug c/49182] New: Fordward declarations of struct not usable in function pointer types brad.lionberger at intel dot com
2011-05-26 23:12 ` [Bug c/49182] " pinskia at gcc dot gnu.org
@ 2011-05-26 23:23 ` pinskia at gcc dot gnu.org
2011-05-26 23:36 ` brad.lionberger at intel dot com
` (3 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: pinskia at gcc dot gnu.org @ 2011-05-26 23:23 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49182
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> 2011-05-26 23:12:03 UTC ---
I forgot to mention GCC compiles it correctly with the C++ front-end.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c/49182] Fordward declarations of struct not usable in function pointer types.
2011-05-26 23:10 [Bug c/49182] New: Fordward declarations of struct not usable in function pointer types brad.lionberger at intel dot com
2011-05-26 23:12 ` [Bug c/49182] " pinskia at gcc dot gnu.org
2011-05-26 23:23 ` pinskia at gcc dot gnu.org
@ 2011-05-26 23:36 ` brad.lionberger at intel dot com
2011-05-26 23:45 ` pinskia at gcc dot gnu.org
` (2 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: brad.lionberger at intel dot com @ 2011-05-26 23:36 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49182
--- Comment #3 from Brad <brad.lionberger at intel dot com> 2011-05-26 23:23:17 UTC ---
(In reply to comment #2)
> I forgot to mention GCC compiles it correctly with the C++ front-end.
Removing the typedefs will still cause compilation to error out not knowing
what a is. For example:
// Forward declaration
struct a;
// Pointer to function with struct as parameter
typedef int (*FxnPointer)(a* WontComplie);
// Actual declaration of struct with function pointer type declared above.
struct _a
{
int foo;
int bar;
FxnPointer PtrToFxn;
} a;
int main(void)
{
return 0;
}
Resutls are :
FxnPtrEx.c:5:28: error: expected ‘)’ before ‘*’ token
FxnPtrEx.c:12:2: error: expected specifier-qualifier-list before ‘FxnPointer’
It seems to not take the forward declaration of the struct as a member of the
parameter list of the FxnPointer type, unless I am missing something here.
What I am trying to do is create a function pointer that takes in as a
parameter a pointer to a structure, but in that structure is a function pointer
of that type. I am confused as to why the forward declaration is not working
here.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c/49182] Fordward declarations of struct not usable in function pointer types.
2011-05-26 23:10 [Bug c/49182] New: Fordward declarations of struct not usable in function pointer types brad.lionberger at intel dot com
` (2 preceding siblings ...)
2011-05-26 23:36 ` brad.lionberger at intel dot com
@ 2011-05-26 23:45 ` pinskia at gcc dot gnu.org
2011-05-26 23:48 ` redi at gcc dot gnu.org
2011-05-27 1:24 ` brad.lionberger at intel dot com
5 siblings, 0 replies; 7+ messages in thread
From: pinskia at gcc dot gnu.org @ 2011-05-26 23:45 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49182
--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> 2011-05-26 23:36:43 UTC ---
This works:
// Forward declaration
typedef struct _a a;
// Pointer to function with struct as parameter
typedef int (*FxnPointer)(a* WontComplie);
// Actual declaration of struct with function pointer type declared above.
struct _a
{
int foo;
int bar;
FxnPointer PtrToFxn;
};
int main(void)
{
a test_struct;
return 0;
}
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c/49182] Fordward declarations of struct not usable in function pointer types.
2011-05-26 23:10 [Bug c/49182] New: Fordward declarations of struct not usable in function pointer types brad.lionberger at intel dot com
` (3 preceding siblings ...)
2011-05-26 23:45 ` pinskia at gcc dot gnu.org
@ 2011-05-26 23:48 ` redi at gcc dot gnu.org
2011-05-27 1:24 ` brad.lionberger at intel dot com
5 siblings, 0 replies; 7+ messages in thread
From: redi at gcc dot gnu.org @ 2011-05-26 23:48 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49182
--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-05-26 23:44:43 UTC ---
(In reply to comment #3)
> (In reply to comment #2)
> > I forgot to mention GCC compiles it correctly with the C++ front-end.
>
> Removing the typedefs will still cause compilation to error out not knowing
> what a is. For example:
>
> // Forward declaration
> struct a;
You've declared the type "struct a"
> // Pointer to function with struct as parameter
> typedef int (*FxnPointer)(a* WontComplie);
You've tried to use "a" which is undeclared
> // Actual declaration of struct with function pointer type declared above.
> struct _a
> {
> int foo;
> int bar;
> FxnPointer PtrToFxn;
> } a;
Now you've declared a variable called "a" with type "struct _a"
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c/49182] Fordward declarations of struct not usable in function pointer types.
2011-05-26 23:10 [Bug c/49182] New: Fordward declarations of struct not usable in function pointer types brad.lionberger at intel dot com
` (4 preceding siblings ...)
2011-05-26 23:48 ` redi at gcc dot gnu.org
@ 2011-05-27 1:24 ` brad.lionberger at intel dot com
5 siblings, 0 replies; 7+ messages in thread
From: brad.lionberger at intel dot com @ 2011-05-27 1:24 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49182
--- Comment #6 from Brad <brad.lionberger at intel dot com> 2011-05-26 23:48:27 UTC ---
(In reply to comment #5)
> (In reply to comment #3)
> > (In reply to comment #2)
> > > I forgot to mention GCC compiles it correctly with the C++ front-end.
> >
> > Removing the typedefs will still cause compilation to error out not knowing
> > what a is. For example:
> >
> > // Forward declaration
> > struct a;
> You've declared the type "struct a"
> > // Pointer to function with struct as parameter
> > typedef int (*FxnPointer)(a* WontComplie);
> You've tried to use "a" which is undeclared
> > // Actual declaration of struct with function pointer type declared above.
> > struct _a
> > {
> > int foo;
> > int bar;
> > FxnPointer PtrToFxn;
> > } a;
> Now you've declared a variable called "a" with type "struct _a"
Ah, I see now! Thank you very much.
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2011-05-26 23:48 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
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2011-05-26 23:10 [Bug c/49182] New: Fordward declarations of struct not usable in function pointer types brad.lionberger at intel dot com
2011-05-26 23:12 ` [Bug c/49182] " pinskia at gcc dot gnu.org
2011-05-26 23:23 ` pinskia at gcc dot gnu.org
2011-05-26 23:36 ` brad.lionberger at intel dot com
2011-05-26 23:45 ` pinskia at gcc dot gnu.org
2011-05-26 23:48 ` redi at gcc dot gnu.org
2011-05-27 1:24 ` brad.lionberger at intel dot com
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