[PATCH v2] Print padding size when aligning struct member

[Vít Kabele]

Hello,

I changed the tested pattern to match even on targets with different
alignment.

BR,
VK

-- >8 --

Announce the size of introduced padding when compiling
with -Wpadded.

gcc/ChangeLog:

        * stor-layout.cc (place_field): Change warning message format

gcc/testsuite/ChangeLog:

        * c-c++-common/Wpadded.c: Add new testcase
        * gcc.dg/Wpadded.c: Update the expected warning message

Signed-off-by: Vít Kabele <vit.kab...@sysgo.com>
---
 gcc/stor-layout.cc                   | 2 +-
 gcc/testsuite/c-c++-common/Wpadded.c | 1 +
 gcc/testsuite/gcc.dg/Wpadded.c       | 2 +-
 3 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/gcc/stor-layout.cc b/gcc/stor-layout.cc
index 45bf2d18639..1d2bd61eeae 100644
--- a/gcc/stor-layout.cc
+++ b/gcc/stor-layout.cc
@@ -1346,7 +1346,7 @@ place_field (record_layout_info rli, tree field)
       if (!targetm.ms_bitfield_layout_p (rli->t)
          && DECL_SOURCE_LOCATION (field) != BUILTINS_LOCATION
          && !TYPE_ARTIFICIAL (rli->t))
-       warning (OPT_Wpadded, "padding struct to align %q+D", field);
+       warning (OPT_Wpadded, "padding struct with %d bytes to align %q+D", 
(desired_align - known_align)/8, field);
 
       /* If the alignment is still within offset_align, just align
         the bit position.  */
diff --git a/gcc/testsuite/c-c++-common/Wpadded.c 
b/gcc/testsuite/c-c++-common/Wpadded.c
index c5be4686822..0818ea03690 100644
--- a/gcc/testsuite/c-c++-common/Wpadded.c
+++ b/gcc/testsuite/c-c++-common/Wpadded.c
@@ -11,4 +11,5 @@
  * 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" } */
+struct R { char c; __UINT32_TYPE__ i; } __attribute__((aligned(4))); /* { 
dg-warning "padding struct with" } */
 
diff --git a/gcc/testsuite/gcc.dg/Wpadded.c b/gcc/testsuite/gcc.dg/Wpadded.c
index 70fcd79a6d4..218b37d1abc 100644
--- a/gcc/testsuite/gcc.dg/Wpadded.c
+++ b/gcc/testsuite/gcc.dg/Wpadded.c
@@ -10,5 +10,5 @@
 
 struct foo {
   char bar;
-  long baz; /* { dg-warning "padding struct to align" ""  { target { ! 
default_packed } } } */
+  long baz; /* { dg-warning "padding struct with" ""  { target { ! 
default_packed } } } */
 } futz;
-- 
2.30.2