From 7a16d39903ed1bf159f7933a19ccae62155b371b Mon Sep 17 00:00:00 2001 From: Vit Kabele Date: Sat, 9 Jul 2022 13:06:43 -0400 Subject: [PATCH] [PATCH v3] c: Extend the -Wpadded message with actual padding size gcc/ChangeLog: * stor-layout.cc (finalize_record_size): Extend warning message. gcc/testsuite/ChangeLog: * c-c++-common/Wpadded.c: New test. --- gcc/stor-layout.cc | 7 ++++++- gcc/testsuite/c-c++-common/Wpadded.c | 14 ++++++++++++++ 2 files changed, 20 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/c-c++-common/Wpadded.c diff --git a/gcc/stor-layout.cc b/gcc/stor-layout.cc index 765f22f68b9f..88923c4136bf 100644 --- a/gcc/stor-layout.cc +++ b/gcc/stor-layout.cc @@ -1781,7 +1781,12 @@ finalize_record_size (record_layout_info rli) && simple_cst_equal (unpadded_size, TYPE_SIZE (rli->t)) == 0 && input_location != BUILTINS_LOCATION && !TYPE_ARTIFICIAL (rli->t)) - warning (OPT_Wpadded, "padding struct size to alignment boundary"); + { + tree pad_size + = size_binop (MINUS_EXPR, TYPE_SIZE_UNIT (rli->t), unpadded_size_unit); + warning (OPT_Wpadded, + "padding struct size to alignment boundary with %E bytes", pad_size); + } if (warn_packed && TREE_CODE (rli->t) == RECORD_TYPE && TYPE_PACKED (rli->t) && ! rli->packed_maybe_necessary diff --git a/gcc/testsuite/c-c++-common/Wpadded.c b/gcc/testsuite/c-c++-common/Wpadded.c new file mode 100644 index 000000000000..c5be46868224 --- /dev/null +++ b/gcc/testsuite/c-c++-common/Wpadded.c @@ -0,0 +1,14 @@ +/* { dg-do compile } */ +/* { dg-options "-Wpadded" } */ + +/* + * The struct is on single line, because C++ compiler emits the -Wpadded + * warning at the first line of the struct definition, while the C compiler at + * the last line. This way the test passes on both. + * + * Attribute aligned is needed for the test to pass on targets where + * the default behaviour is to pack the struct and also on targets that align + * 4 byte fields to 2 byte boundary. + */ +struct S { __UINT32_TYPE__ i; char c; } __attribute__((aligned(4))); /* { dg-warning "padding struct size to alignment boundary with 3 bytes" } */ + -- 2.47.2