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* [Bug c/54454] New: gcc violates c99 specification w.r.t. flexible arrays @ 2012-09-02 1:36 mikulas at artax dot karlin.mff.cuni.cz 2012-09-02 1:53 ` [Bug c/54454] " mikulas at artax dot karlin.mff.cuni.cz ` (3 more replies) 0 siblings, 4 replies; 5+ messages in thread From: mikulas at artax dot karlin.mff.cuni.cz @ 2012-09-02 1:36 UTC (permalink / raw) To: gcc-bugs http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54454 Bug #: 54454 Summary: gcc violates c99 specification w.r.t. flexible arrays Classification: Unclassified Product: gcc Version: 4.7.1 Status: UNCONFIRMED Severity: minor Priority: P3 Component: c AssignedTo: unassigned@gcc.gnu.org ReportedBy: mikulas@artax.karlin.mff.cuni.cz Host: hppa-linux-gnu Target: hppa-linux-gnu Build: hppa-linux-gnu The c99 specification says (section 6.7.2.1, paragraph 16): "The size of the structure [with flexible array member] shall be equal to the offset of the last element of an otherwise identical structure that replaces the flexible array member with an array of unspecified length". This is not true in gcc. Try to complile and run this program: the size of the structure with the flexible array member is 8. However, offset of the flexible array member is 6. According to the specification, sizeof(struct flexible) should be 6. #include <stdio.h> #include <stddef.h> struct flexible { unsigned a; unsigned short b; unsigned char array[]; }; struct not_flexible { unsigned a; unsigned short b; unsigned char array[1]; }; int main(void) { printf("sizeof(struct flexible) = %d\n", (int)sizeof(struct flexible)); printf("offsetof(struct not_flexible, array)) = %d\n", (int)offsetof(struct not_flexible, array)); printf("offsetof(struct flexible, array)) = %d\n", (int)offsetof(struct flexible, array)); return 0; } ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c/54454] gcc violates c99 specification w.r.t. flexible arrays 2012-09-02 1:36 [Bug c/54454] New: gcc violates c99 specification w.r.t. flexible arrays mikulas at artax dot karlin.mff.cuni.cz @ 2012-09-02 1:53 ` mikulas at artax dot karlin.mff.cuni.cz 2012-09-02 2:06 ` pinskia at gcc dot gnu.org ` (2 subsequent siblings) 3 siblings, 0 replies; 5+ messages in thread From: mikulas at artax dot karlin.mff.cuni.cz @ 2012-09-02 1:53 UTC (permalink / raw) To: gcc-bugs http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54454 --- Comment #1 from mikulas at artax dot karlin.mff.cuni.cz 2012-09-02 01:52:54 UTC --- Another specification violation: section 6.7.2.1 paragraph 20 says that assignment of a structure with flexible array member doesn't copy any of the array elements. In gcc it is buggy because it copies some array elements. Try this: #include <stdio.h> #include <stdlib.h> #include <string.h> struct flexible { unsigned a; unsigned short b; unsigned char array[]; }; int main(void) { struct flexible *f1, *f2; f1 = malloc(sizeof(struct flexible) + 3); f1->array[0] = 0; f1->array[1] = 0; f1->array[2] = 0; f2 = malloc(sizeof(struct flexible) + 3); f2->array[0] = 1; f2->array[1] = 1; f2->array[2] = 1; *f2 = *f1; printf("f2->array[0] == %d (should be 1)\n", f2->array[0]); printf("f2->array[1] == %d (should be 1)\n", f2->array[1]); printf("f2->array[2] == %d (should be 1)\n", f2->array[2]); return 0; } ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c/54454] gcc violates c99 specification w.r.t. flexible arrays 2012-09-02 1:36 [Bug c/54454] New: gcc violates c99 specification w.r.t. flexible arrays mikulas at artax dot karlin.mff.cuni.cz 2012-09-02 1:53 ` [Bug c/54454] " mikulas at artax dot karlin.mff.cuni.cz @ 2012-09-02 2:06 ` pinskia at gcc dot gnu.org 2012-09-02 12:20 ` jsm28 at gcc dot gnu.org 2024-03-14 20:20 ` pinskia at gcc dot gnu.org 3 siblings, 0 replies; 5+ messages in thread From: pinskia at gcc dot gnu.org @ 2012-09-02 2:06 UTC (permalink / raw) To: gcc-bugs http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54454 --- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> 2012-09-02 02:05:47 UTC --- I think this comes down to alignment. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c/54454] gcc violates c99 specification w.r.t. flexible arrays 2012-09-02 1:36 [Bug c/54454] New: gcc violates c99 specification w.r.t. flexible arrays mikulas at artax dot karlin.mff.cuni.cz 2012-09-02 1:53 ` [Bug c/54454] " mikulas at artax dot karlin.mff.cuni.cz 2012-09-02 2:06 ` pinskia at gcc dot gnu.org @ 2012-09-02 12:20 ` jsm28 at gcc dot gnu.org 2024-03-14 20:20 ` pinskia at gcc dot gnu.org 3 siblings, 0 replies; 5+ messages in thread From: jsm28 at gcc dot gnu.org @ 2012-09-02 12:20 UTC (permalink / raw) To: gcc-bugs http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54454 Joseph S. Myers <jsm28 at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |RESOLVED Resolution| |INVALID --- Comment #3 from Joseph S. Myers <jsm28 at gcc dot gnu.org> 2012-09-02 12:20:39 UTC --- All the text you are quoting changed in TC2 following DR 282. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c/54454] gcc violates c99 specification w.r.t. flexible arrays 2012-09-02 1:36 [Bug c/54454] New: gcc violates c99 specification w.r.t. flexible arrays mikulas at artax dot karlin.mff.cuni.cz ` (2 preceding siblings ...) 2012-09-02 12:20 ` jsm28 at gcc dot gnu.org @ 2024-03-14 20:20 ` pinskia at gcc dot gnu.org 3 siblings, 0 replies; 5+ messages in thread From: pinskia at gcc dot gnu.org @ 2024-03-14 20:20 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=54454 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Resolution|INVALID |DUPLICATE --- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> --- Dup. *** This bug has been marked as a duplicate of bug 9058 *** ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2024-03-14 20:20 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2012-09-02 1:36 [Bug c/54454] New: gcc violates c99 specification w.r.t. flexible arrays mikulas at artax dot karlin.mff.cuni.cz 2012-09-02 1:53 ` [Bug c/54454] " mikulas at artax dot karlin.mff.cuni.cz 2012-09-02 2:06 ` pinskia at gcc dot gnu.org 2012-09-02 12:20 ` jsm28 at gcc dot gnu.org 2024-03-14 20:20 ` pinskia at gcc dot gnu.org
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