Print padding size when aligning struct member
Commit Message
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.kabele@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(-)
Comments
On Feb 07 2023, Vít Kabele wrote:
> diff --git a/gcc/testsuite/gcc.dg/Wpadded.c b/gcc/testsuite/gcc.dg/Wpadded.c
> index 70fcd79a6d4..357e7f61e4a 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 7 bytes to align" "" { target { ! default_packed } } } */
The actual amount of padding is target dependent.
On Tue, Feb 07, 2023 at 02:08:35PM +0100, Andreas Schwab wrote:
> On Feb 07 2023, Vít Kabele wrote:
>
> > diff --git a/gcc/testsuite/gcc.dg/Wpadded.c b/gcc/testsuite/gcc.dg/Wpadded.c
> > index 70fcd79a6d4..357e7f61e4a 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 7 bytes to align" "" { target { ! default_packed } } } */
>
> The actual amount of padding is target dependent.
Ah sorry, would removing everything after `with...` be ok?
Like this:
> + long baz; /* { dg-warning "padding struct with" "" { target { ! default_packed } } } */
@@ -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. */
@@ -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 3 bytes to align 'i'" } */
@@ -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 7 bytes to align" "" { target { ! default_packed } } } */
} futz;