From 0c91f28eb08a571878b9390f17d0bd98765eb559 Mon Sep 17 00:00:00 2001 From: Jakub Jelinek Date: Mon, 25 Jun 2018 19:21:47 +0200 Subject: [PATCH] backport: re PR c/82210 (Having _Alignas in a struct with VLAs causes writing to one array to overwrite another) Backported from mainline 2018-02-13 Jakub Jelinek PR c/82210 * stor-layout.c (place_field): For variable length fields, adjust offset_align afterwards not just based on the field's alignment, but also on the size. * gcc.c-torture/execute/pr82210.c: New test. From-SVN: r262063 --- gcc/ChangeLog | 7 +++++ gcc/stor-layout.c | 25 ++++++++++++++++++ gcc/testsuite/ChangeLog | 5 ++++ gcc/testsuite/gcc.c-torture/execute/pr82210.c | 26 +++++++++++++++++++ 4 files changed, 63 insertions(+) create mode 100644 gcc/testsuite/gcc.c-torture/execute/pr82210.c diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 1c0d9b840732..88eabb9420ba 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,6 +1,13 @@ 2018-06-25 Jakub Jelinek Backported from mainline + 2018-02-13 Jakub Jelinek + + PR c/82210 + * stor-layout.c (place_field): For variable length fields, adjust + offset_align afterwards not just based on the field's alignment, + but also on the size. + 2018-02-10 Jakub Jelinek PR sanitizer/83987 diff --git a/gcc/stor-layout.c b/gcc/stor-layout.c index dd40ca00af8e..2aa93258a185 100644 --- a/gcc/stor-layout.c +++ b/gcc/stor-layout.c @@ -1519,6 +1519,31 @@ place_field (record_layout_info rli, tree field) = size_binop (PLUS_EXPR, rli->offset, DECL_SIZE_UNIT (field)); rli->bitpos = bitsize_zero_node; rli->offset_align = MIN (rli->offset_align, desired_align); + + if (!multiple_of_p (bitsizetype, DECL_SIZE (field), + bitsize_int (rli->offset_align))) + { + tree type = strip_array_types (TREE_TYPE (field)); + /* The above adjusts offset_align just based on the start of the + field. The field might not have a size that is a multiple of + that offset_align though. If the field is an array of fixed + sized elements, assume there can be any multiple of those + sizes. If it is a variable length aggregate or array of + variable length aggregates, assume worst that the end is + just BITS_PER_UNIT aligned. */ + if (TREE_CODE (TYPE_SIZE (type)) == INTEGER_CST) + { + if (TREE_INT_CST_LOW (TYPE_SIZE (type))) + { + unsigned HOST_WIDE_INT sz + = TREE_INT_CST_LOW (TYPE_SIZE (type)); + sz = sz & -sz; + rli->offset_align = MIN (rli->offset_align, sz); + } + } + else + rli->offset_align = MIN (rli->offset_align, BITS_PER_UNIT); + } } else if (targetm.ms_bitfield_layout_p (rli->t)) { diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index 4e92dc30240d..029e88d43fed 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,6 +1,11 @@ 2018-06-25 Jakub Jelinek Backported from mainline + 2018-02-13 Jakub Jelinek + + PR c/82210 + * gcc.c-torture/execute/pr82210.c: New test. + 2018-02-12 Jakub Jelinek PR c++/84341 diff --git a/gcc/testsuite/gcc.c-torture/execute/pr82210.c b/gcc/testsuite/gcc.c-torture/execute/pr82210.c new file mode 100644 index 000000000000..48fb715570ad --- /dev/null +++ b/gcc/testsuite/gcc.c-torture/execute/pr82210.c @@ -0,0 +1,26 @@ +/* PR c/82210 */ + +void +foo (int size) +{ + int i; + struct S { + __attribute__((aligned (16))) struct T { short c; } a[size]; + int b[size]; + } s; + + for (i = 0; i < size; i++) + s.a[i].c = 0x1234; + for (i = 0; i < size; i++) + s.b[i] = 0; + for (i = 0; i < size; i++) + if (s.a[i].c != 0x1234 || s.b[i] != 0) + __builtin_abort (); +} + +int +main () +{ + foo (15); + return 0; +} -- 2.47.2