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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) -- links below jump to the message on this page -- 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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