| Message ID | 20141010104615.GG10376@tucnak.redhat.com |
|---|---|
| State | New |
| Headers | show |
On Fri, 10 Oct 2014, Jakub Jelinek wrote: > Hi! > > As the testcase shows, _Alignof can sometimes return smaller number > than the minimum alignment. That is because when laying out structures, > fields with types with TYPE_USER_ALIGN set have also DECL_USER_ALIGN > set and therefore neither BIGGEST_FIELD_ALIGNMENT nor ADJUST_FIELD_ALIGN > is applied to them, but min_align_of_type was applying that unconditionally. > > Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for > trunk/4.9? > > 2014-10-10 Jakub Jelinek <jakub@redhat.com> > > PR c/63495 > * stor-layout.c (min_align_of_type): Don't decrease alignment > through BIGGEST_FIELD_ALIGNMENT or ADJUST_FIELD_ALIGN if > TYPE_USER_ALIGN is set. > > * gcc.target/i386/pr63495.c: New test. OK.
--- gcc/stor-layout.c.jj 2014-09-01 09:43:56.000000000 +0200 +++ gcc/stor-layout.c 2014-10-09 09:56:49.760893630 +0200 @@ -2400,17 +2400,19 @@ min_align_of_type (tree type) { unsigned int align = TYPE_ALIGN (type); align = MIN (align, BIGGEST_ALIGNMENT); + if (!TYPE_USER_ALIGN (type)) + { #ifdef BIGGEST_FIELD_ALIGNMENT - align = MIN (align, BIGGEST_FIELD_ALIGNMENT); + align = MIN (align, BIGGEST_FIELD_ALIGNMENT); #endif - unsigned int field_align = align; + unsigned int field_align = align; #ifdef ADJUST_FIELD_ALIGN - tree field = build_decl (UNKNOWN_LOCATION, FIELD_DECL, NULL_TREE, - type); - field_align = ADJUST_FIELD_ALIGN (field, field_align); - ggc_free (field); + tree field = build_decl (UNKNOWN_LOCATION, FIELD_DECL, NULL_TREE, type); + field_align = ADJUST_FIELD_ALIGN (field, field_align); + ggc_free (field); #endif - align = MIN (align, field_align); + align = MIN (align, field_align); + } return align / BITS_PER_UNIT; } --- gcc/testsuite/gcc.target/i386/pr63495.c.jj 2014-10-09 09:59:46.036634365 +0200 +++ gcc/testsuite/gcc.target/i386/pr63495.c 2014-10-09 10:01:09.231096165 +0200 @@ -0,0 +1,6 @@ +/* PR c/63495 */ +/* { dg-do compile { target { i?86-*-linux* x86_64-*-linux* } } } */ +/* { dg-options "-std=gnu11" } */ + +struct __attribute__ ((aligned (8))) S { char c; }; +_Static_assert (_Alignof (struct S) >= 8, "wrong alignment");