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* [gcc r13-1588] [PATCH v3] c: Extend the -Wpadded message with actual padding size
@ 2022-07-09 17:07 Jeff Law
0 siblings, 0 replies; only message in thread
From: Jeff Law @ 2022-07-09 17:07 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:7a16d39903ed1bf159f7933a19ccae62155b371b
commit r13-1588-g7a16d39903ed1bf159f7933a19ccae62155b371b
Author: Vit Kabele <vit.kabele@sysgo.com>
Date: Sat Jul 9 13:06:43 2022 -0400
[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.
Diff:
---
gcc/stor-layout.cc | 7 ++++++-
gcc/testsuite/c-c++-common/Wpadded.c | 14 ++++++++++++++
2 files changed, 20 insertions(+), 1 deletion(-)
diff --git a/gcc/stor-layout.cc b/gcc/stor-layout.cc
index 765f22f68b9..88923c4136b 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 00000000000..c5be4686822
--- /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" } */
+
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