[Bug c++/71912] [6/7 regression] flexible array in struct in union rejected
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71912 --- Comment #7 from Martin Sebor --- Author: msebor Date: Thu Oct 13 22:26:36 2016 New Revision: 241143 URL: https://gcc.gnu.org/viewcvs?rev=241143=gcc=rev Log: PR c++/71912 - [6/7 regression] flexible array in struct in union rejected gcc/cp/ChangeLog: PR c++/71912 * class.c (struct flexmems_t): Add members. (find_flexarrays): Add arguments. Correct handling of anonymous structs. (diagnose_flexarrays): Adjust to issue warnings in addition to errors. (check_flexarrays): Add argument. (diagnose_invalid_flexarray): New functions. gcc/testsuite/ChangeLog: PR c++/71912 * g++.dg/ext/flexary4.C: Adjust. * g++.dg/ext/flexary5.C: Same. * g++.dg/ext/flexary9.C: Same. * g++.dg/ext/flexary19.C: New test. * g++.dg/ext/flexary18.C: New test. * g++.dg/torture/pr64312.C: Add a dg-error directive to an ill-formed regression test. * g++.dg/compat/struct-layout-1_generate.c (subfield): Add argument. Avoid generating a flexible array member in an array. Added: trunk/gcc/testsuite/g++.dg/ext/flexary18.C trunk/gcc/testsuite/g++.dg/ext/flexary19.C Modified: trunk/gcc/cp/ChangeLog trunk/gcc/cp/class.c trunk/gcc/testsuite/ChangeLog trunk/gcc/testsuite/g++.dg/compat/struct-layout-1_generate.c trunk/gcc/testsuite/g++.dg/ext/flexary4.C trunk/gcc/testsuite/g++.dg/ext/flexary5.C trunk/gcc/testsuite/g++.dg/ext/flexary9.C trunk/gcc/testsuite/g++.dg/torture/pr64312.C
[Bug c++/71912] [6/7 regression] flexible array in struct in union rejected
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71912 Andrew Pinski changed: What|Removed |Added Target Milestone|--- |6.3
[Bug c++/71912] [6/7 regression] flexible array in struct in union rejected
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71912 --- Comment #6 from Martin Sebor --- Patch posted for review: https://gcc.gnu.org/ml/gcc-patches/2016-07/msg01505.html
[Bug c++/71912] [6/7 regression] flexible array in struct in union rejected
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71912 Martin Sebor changed: What|Removed |Added Blocks||69698 Severity|normal |minor --- Comment #5 from Martin Sebor --- (In reply to Martin Sebor from comment #4) > Even though GCC with -Wpedantic silently accepts the equivalent definition > of struct xyyzy, it issues a diagnostic for baz supporting the > interpretation above: > > warning: invalid use of structure with flexible array member > > Since the struct definitions are equivalent, it seems that either they both > should be diagnosed or neither should be. Let me correct the above. GCC does give a pedantic warning in both cases confirming that the test case is, strictly speaking, invalid. (I must have missed it somehow.) Clang too diagnoses it with -Wflexible-array-extensions: warning: 'u' may not be nested in a struct due to flexible array I'm lowering the Severity to Minor but I will fix the C++ error for compatibility with GCC. Referenced Bugs: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69698 [Bug 69698] [meta-bug] flexible array members
[Bug c++/71912] [6/7 regression] flexible array in struct in union rejected
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71912 Martin Sebor changed: What|Removed |Added Status|UNCONFIRMED |ASSIGNED Last reconfirmed||2016-07-18 Known to work||5.4.0 Assignee|unassigned at gcc dot gnu.org |msebor at gcc dot gnu.org Summary|flexible array in union |[6/7 regression] flexible ||array in struct in union ||rejected Ever confirmed|0 |1 Known to fail||6.1.0, 7.0 --- Comment #4 from Martin Sebor --- I confirm the code in the test case is meant to be accepted by G++ for compatibility with GCC but is rejected due to a bug in the find_flexarrays function in class.c. That said, it's not completely clear that the code is valid according to the C definition of a flexible array member: As a special case, the last element of a structure with more than one named member may have an incomplete array type; this is called a /flexible array member/. Although C doesn't define the term element, I think it means the last declared subobject of an object. In the test case, neither of the two flexible array members is the last element of struct xyyzy (the last element is the subobject u). Within the member u of struct xyyzy, the flexible array member f.s is not the last element of the structure xyyzy (b.t is the last element). Even though GCC with -Wpedantic silently accepts the equivalent definition of struct xyyzy, it issues a diagnostic for baz supporting the interpretation above: warning: invalid use of structure with flexible array member Since the struct definitions are equivalent, it seems that either they both should be diagnosed or neither should be.
