Add warn_if_not_aligned attribute

Add warn_if_not_aligned attribute as well as  command line options:
-Wif-not-aligned and -Wpacked-not-aligned.

__attribute__((warn_if_not_aligned(N))) causes compiler to issue a
warning if the field in a struct or union is not aligned to N:

typedef unsigned long long __u64
  __attribute__((aligned(4),warn_if_not_aligned(8)));

struct foo
{
  int i1;
  int i2;
  __u64 x;
};

__u64 is aligned to 4 bytes.  But inside struct foo, __u64 should be
aligned at 8 bytes.  It is used to define struct foo in such a way that
struct foo has the same layout and x has the same alignment when __u64
is aligned at either 4 or 8 bytes.

Since struct foo is normally aligned to 4 bytes, a warning will be issued:

warning: alignment 4 of 'struct foo' is less than 8

Align struct foo to 8 bytes:

struct foo
{
  int i1;
  int i2;
  __u64 x;
} __attribute__((aligned(8)));

silences the warning.  It also warns the field with misaligned offset:

struct foo
{
  int i1;
  int i2;
  int i3;
  __u64 x;
} __attribute__((aligned(8)));

warning: 'x' offset 12 in 'struct foo' isn't aligned to 8

This warning is controlled by -Wif-not-aligned and is enabled by default.

When -Wpacked-not-aligned is used, the same warning is also issued for
the field with explicitly specified alignment in a packed struct or union:

struct __attribute__ ((aligned (8))) S8 { char a[8]; };
struct __attribute__ ((packed)) S {
  struct S8 s8;
};

warning: alignment 1 of 'struct S' is less than 8

This warning is disabled by default and enabled by -Wall.

gcc/

	PR c/53037
	* print-tree.c (print_node): Support DECL_WARN_IF_NOT_ALIGN
	and TYPE_WARN_IF_NOT_ALIGN.
	* stor-layout.c (do_type_align): Merge DECL_WARN_IF_NOT_ALIGN.
	(handle_warn_if_not_align): New.
	(place_union_field): Call handle_warn_if_not_align.
	(place_field): Call handle_warn_if_not_align.  Copy
	TYPE_WARN_IF_NOT_ALIGN.
	(finish_builtin_struct): Copy TYPE_WARN_IF_NOT_ALIGN.
	(layout_type): Likewise.
	* tree-core.h (tree_type_common): Add warn_if_not_align.  Set
	spare to 18.
	(tree_decl_common): Add warn_if_not_align.
	* tree.c (build_range_type_1): Copy TYPE_WARN_IF_NOT_ALIGN.
	* tree.h (TYPE_WARN_IF_NOT_ALIGN): New.
	(SET_TYPE_WARN_IF_NOT_ALIGN): Likewise.
	(DECL_WARN_IF_NOT_ALIGN): Likewise.
	(SET_DECL_WARN_IF_NOT_ALIGN): Likewise.
	* doc/extend.texi: Document warn_if_not_aligned attribute.
	* doc/invoke.texi: Document -Wif-not-aligned and
	-Wpacked-not-aligned.

gcc/c-family/

	PR c/53037
	* c-attribs.c (handle_warn_if_not_aligned_attribute): New.
	(c_common_attribute_table): Add warn_if_not_aligned.
	(handle_aligned_attribute): Renamed to ...
	(common_handle_aligned_attribute): Remove argument, name, and add
	argument, warn_if_not_aligned.  Handle warn_if_not_aligned.
	(handle_aligned_attribute): New.
	* c.opt: Add -Wif-not-aligned and -Wpacked-not-aligned.

gcc/c/

	PR c/53037
	* c-decl.c (merge_decls): Also merge DECL_WARN_IF_NOT_ALIGN.
	(check_bitfield_type_and_width): Don't allow bit-field with
	warn_if_not_aligned type.

gcc/cp/

	PR c/53037
	* decl.c (duplicate_decls): Also merge DECL_WARN_IF_NOT_ALIGN.
	* decl2.c (grokbitfield): Don't allow bit-field with
	warn_if_not_aligned type.

gcc/testsuite/

	PR c/53037
	* c-c++-common/pr53037-5.c: New test.
	* g++.dg/pr53037-1.C: Likewise.
	* g++.dg/pr53037-2.C: Likewise.
	* g++.dg/pr53037-3.C: Likewise.
	* g++.dg/pr53037-4.C: Likewise.
	* gcc.dg/pr53037-1.c: Likewise.
	* gcc.dg/pr53037-2.c: Likewise.
	* gcc.dg/pr53037-3.c: Likewise.
	* gcc.dg/pr53037-4.c: Likewise.

From-SVN: r251180

10 files changed, 452 insertions, 0 deletions

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 9020770..bcf2495 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,16 @@
+2017-08-18  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR c/53037
+	* c-c++-common/pr53037-5.c: New test.
+	* g++.dg/pr53037-1.C: Likewise.
+	* g++.dg/pr53037-2.C: Likewise.
+	* g++.dg/pr53037-3.C: Likewise.
+	* g++.dg/pr53037-4.C: Likewise.
+	* gcc.dg/pr53037-1.c: Likewise.
+	* gcc.dg/pr53037-2.c: Likewise.
+	* gcc.dg/pr53037-3.c: Likewise.
+	* gcc.dg/pr53037-4.c: Likewise.
+
 2017-08-17  Peter Bergner  <bergner@vnet.ibm.com>
 
 	* gcc.target/powerpc/p8vector-int128-1.c: Remove use of -mvsx-timode.
diff --git a/gcc/testsuite/c-c++-common/pr53037-5.c b/gcc/testsuite/c-c++-common/pr53037-5.c
new file mode 100644
index 0000000..97d54b1
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/pr53037-5.c
@@ -0,0 +1,81 @@
+/* PR c/53037.  */
+/* { dg-do compile } */
+/* { dg-options "-O0 -Wno-if-not-aligned" } */
+
+typedef unsigned long long __u64
+  __attribute__((aligned(4),warn_if_not_aligned(8)));
+
+struct foo1
+{
+  int i1;
+  int i2;
+  int i3;
+  __u64 x;
+};
+
+struct foo2
+{
+  int i1;
+  int i2;
+  int i3;
+  __u64 x;
+} __attribute__((aligned(8)));
+
+struct foo3
+{
+  int i1;
+  int i3;
+  __u64 x;
+};
+
+struct foo4
+{
+  int i1;
+  int i2;
+  __u64 x;
+} __attribute__((aligned(8)));
+
+struct foo5
+{
+  int i1;
+  int x __attribute__((warn_if_not_aligned(16)));
+};
+
+struct foo6
+{
+  int i1;
+  int x __attribute__((warn_if_not_aligned(16))); 
+} __attribute__((aligned(16)));
+
+struct foo7
+{
+  int i1;
+  int i2;
+  int i3;
+  int i4;
+  int x __attribute__((warn_if_not_aligned(16)));
+} __attribute__((aligned(16)));
+
+union bar1
+{
+  int i1;
+  __u64 x;
+};
+
+union bar2
+{
+  int i1;
+  __u64 x;
+} __attribute__((aligned(8)));
+
+union bar3
+{
+  int i1;
+  int x __attribute__((warn_if_not_aligned(16))); 
+};
+
+union bar4
+{
+  int i1;
+  int x __attribute__((warn_if_not_aligned(16)));
+} __attribute__((aligned(16)));
diff --git a/gcc/testsuite/g++.dg/pr53037-1.C b/gcc/testsuite/g++.dg/pr53037-1.C
new file mode 100644
index 0000000..a3d8f99
--- /dev/null
+++ b/gcc/testsuite/g++.dg/pr53037-1.C
@@ -0,0 +1,81 @@
+/* PR c/53037.  */
+/* { dg-do compile } */
+/* { dg-options "-O0" } */
+
+typedef unsigned long long __u64
+  __attribute__((aligned(4),warn_if_not_aligned(8)));
+
+struct foo1 /* { dg-warning "alignment 4 of 'foo1' is less than 8" } */
+{
+  int i1;
+  int i2;
+  int i3;
+  __u64 x; /* { dg-warning "'foo1::x' offset 12 in 'foo1' isn't aligned to 8" } */
+};
+
+struct foo2
+{
+  int i1;
+  int i2;
+  int i3;
+  __u64 x; /* { dg-warning "'foo2::x' offset 12 in 'foo2' isn't aligned to 8" } */
+} __attribute__((aligned(8)));
+
+struct foo3 /* { dg-warning "alignment 4 of 'foo3' is less than 8" } */
+{
+  int i1;
+  int i3;
+  __u64 x;
+};
+
+struct foo4
+{
+  int i1;
+  int i2;
+  __u64 x;
+} __attribute__((aligned(8)));
+
+struct foo5 /* { dg-warning "alignment 4 of 'foo5' is less than 16" } */
+{
+  int i1;
+  int x __attribute__((warn_if_not_aligned(16))); /* { dg-warning "'foo5::x' offset 4 in 'foo5' isn't aligned to 16" } */
+};
+
+struct foo6
+{
+  int i1;
+  int x __attribute__((warn_if_not_aligned(16))); /* { dg-warning "'foo6::x' offset 4 in 'foo6' isn't aligned to 16" } */
+} __attribute__((aligned(16)));
+
+struct foo7
+{
+  int i1;
+  int i2;
+  int i3;
+  int i4;
+  int x __attribute__((warn_if_not_aligned(16)));
+} __attribute__((aligned(16)));
+
+union bar1 /* { dg-warning "alignment 4 of 'bar1' is less than 8" } */
+{
+  int i1;
+  __u64 x;
+};
+
+union bar2
+{
+  int i1;
+  __u64 x;
+} __attribute__((aligned(8)));
+
+union bar3 /* { dg-warning "alignment 4 of 'bar3' is less than 16" } */
+{
+  int i1;
+  int x __attribute__((warn_if_not_aligned(16))); 
+};
+
+union bar4
+{
+  int i1;
+  int x __attribute__((warn_if_not_aligned(16)));
+} __attribute__((aligned(16)));
diff --git a/gcc/testsuite/g++.dg/pr53037-2.C b/gcc/testsuite/g++.dg/pr53037-2.C
new file mode 100644
index 0000000..e617f90
--- /dev/null
+++ b/gcc/testsuite/g++.dg/pr53037-2.C
@@ -0,0 +1,37 @@
+/* PR c/53037.  */
+/* { dg-do compile } */
+/* { dg-options "-O0 -Wpacked-not-aligned" } */
+
+struct __attribute__ ((aligned (8))) S8 { char a[8]; };
+struct __attribute__ ((packed)) S1 { /* { dg-warning "alignment 1 of 'S1' is less than 8" } */
+  struct S8 s8;
+};
+
+struct __attribute__ ((packed, aligned (8))) S2 {
+  struct S8 s8;
+};
+
+struct __attribute__ ((packed, aligned (8))) S3 {
+  int i1;
+  struct S8 s8; /* { dg-warning "'S3::s8' offset 4 in 'S3' isn't aligned to 8" } */
+};
+
+struct __attribute__ ((packed, aligned (8))) S4 {
+  int i1;
+  int i2;
+  struct S8 s8;
+};
+
+struct __attribute__ ((packed)) S5 {
+   long long ll;
+};
+
+union __attribute__ ((packed)) U1 { /* { dg-warning "alignment 1 of 'U1' is less than 8" } */
+  int i1;
+  struct S8 s8;
+};
+
+union __attribute__ ((packed, aligned (8))) U2 {
+  int i1;
+  struct S8 s8;
+};
diff --git a/gcc/testsuite/g++.dg/pr53037-3.C b/gcc/testsuite/g++.dg/pr53037-3.C
new file mode 100644
index 0000000..1ed6354
--- /dev/null
+++ b/gcc/testsuite/g++.dg/pr53037-3.C
@@ -0,0 +1,37 @@
+/* PR c/53037.  */
+/* { dg-do compile } */
+/* { dg-options "-O0 -Wall" } */
+
+struct __attribute__ ((aligned (8))) S8 { char a[8]; };
+struct __attribute__ ((packed)) S1 { /* { dg-warning "alignment 1 of 'S1' is less than 8" } */
+  struct S8 s8;
+};
+
+struct __attribute__ ((packed, aligned (8))) S2 {
+  struct S8 s8;
+};
+
+struct __attribute__ ((packed, aligned (8))) S3 {
+  int i1;
+  struct S8 s8; /* { dg-warning "'S3::s8' offset 4 in 'S3' isn't aligned to 8" } */
+};
+
+struct __attribute__ ((packed, aligned (8))) S4 {
+  int i1;
+  int i2;
+  struct S8 s8;
+};
+
+struct __attribute__ ((packed)) S5 {
+   long long ll;
+};
+
+union __attribute__ ((packed)) U1 { /* { dg-warning "alignment 1 of 'U1' is less than 8" } */
+  int i1;
+  struct S8 s8;
+};
+
+union __attribute__ ((packed, aligned (8))) U2 {
+  int i1;
+  struct S8 s8;
+};
diff --git a/gcc/testsuite/g++.dg/pr53037-4.C b/gcc/testsuite/g++.dg/pr53037-4.C
new file mode 100644
index 0000000..553dd9a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/pr53037-4.C
@@ -0,0 +1,24 @@
+/* PR c/53037.  */
+/* { dg-do compile } */
+/* { dg-options "-O0" } */
+
+int foo1 __attribute__((warn_if_not_aligned(8))); /* { dg-error "'warn_if_not_aligned' may not be specified for 'foo1'" } */
+
+__attribute__((warn_if_not_aligned(8)))
+void
+foo2 (void) /* { dg-error "'warn_if_not_aligned' may not be specified for 'void foo2\\(\\)'" } */
+{
+}
+
+struct foo3
+{
+  int i : 2 __attribute__((warn_if_not_aligned(8))); /* { dg-error "'warn_if_not_aligned' may not be specified for 'i'" } */
+};
+
+typedef unsigned int __u32
+  __attribute__((aligned(4),warn_if_not_aligned(8)));
+
+struct foo4
+{
+  __u32 i : 2; /* { dg-error "cannot declare bit-field 'i' with 'warn_if_not_aligned' type" } */
+};
diff --git a/gcc/testsuite/gcc.dg/pr53037-1.c b/gcc/testsuite/gcc.dg/pr53037-1.c
new file mode 100644
index 0000000..93af0a5
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr53037-1.c
@@ -0,0 +1,81 @@
+/* PR c/53037.  */
+/* { dg-do compile } */
+/* { dg-options "-O0" } */
+
+typedef unsigned long long __u64
+  __attribute__((aligned(4),warn_if_not_aligned(8)));
+
+struct foo1
+{
+  int i1;
+  int i2;
+  int i3;
+  __u64 x; /* { dg-warning "'x' offset 12 in 'struct foo1' isn't aligned to 8" } */
+}; /* { dg-warning "alignment 4 of 'struct foo1' is less than 8" } */
+
+struct foo2
+{
+  int i1;
+  int i2;
+  int i3;
+  __u64 x; /* { dg-warning "'x' offset 12 in 'struct foo2' isn't aligned to 8" } */
+} __attribute__((aligned(8)));
+
+struct foo3
+{
+  int i1;
+  int i3;
+  __u64 x;
+}; /* { dg-warning "alignment 4 of 'struct foo3' is less than 8" } */
+
+struct foo4
+{
+  int i1;
+  int i2;
+  __u64 x;
+} __attribute__((aligned(8)));
+
+struct foo5
+{
+  int i1;
+  int x __attribute__((warn_if_not_aligned(16))); /* { dg-warning "'x' offset 4 in 'struct foo5' isn't aligned to 16" } */
+}; /* { dg-warning "alignment 4 of 'struct foo5' is less than 16" } */
+
+struct foo6
+{
+  int i1;
+  int x __attribute__((warn_if_not_aligned(16))); /* { dg-warning "'x' offset 4 in 'struct foo6' isn't aligned to 16" } */
+} __attribute__((aligned(16)));
+
+struct foo7
+{
+  int i1;
+  int i2;
+  int i3;
+  int i4;
+  int x __attribute__((warn_if_not_aligned(16)));
+} __attribute__((aligned(16)));
+
+union bar1
+{
+  int i1;
+  __u64 x;
+}; /* { dg-warning "alignment 4 of 'union bar1' is less than 8" } */
+
+union bar2
+{
+  int i1;
+  __u64 x;
+} __attribute__((aligned(8)));
+
+union bar3
+{
+  int i1;
+  int x __attribute__((warn_if_not_aligned(16))); 
+}; /* { dg-warning "alignment 4 of 'union bar3' is less than 16" } */
+
+union bar4
+{
+  int i1;
+  int x __attribute__((warn_if_not_aligned(16)));
+} __attribute__((aligned(16)));
diff --git a/gcc/testsuite/gcc.dg/pr53037-2.c b/gcc/testsuite/gcc.dg/pr53037-2.c
new file mode 100644
index 0000000..f9934a6
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr53037-2.c
@@ -0,0 +1,37 @@
+/* PR c/53037.  */
+/* { dg-do compile } */
+/* { dg-options "-O0 -Wpacked-not-aligned" } */
+
+struct __attribute__ ((aligned (8))) S8 { char a[8]; };
+struct __attribute__ ((packed)) S1 {
+  struct S8 s8;
+}; /* { dg-warning "alignment 1 of 'struct S1' is less than 8" } */
+
+struct __attribute__ ((packed, aligned (8))) S2 {
+  struct S8 s8;
+};
+
+struct __attribute__ ((packed, aligned (8))) S3 {
+  int i1;
+  struct S8 s8; /* { dg-warning "'s8' offset 4 in 'struct S3' isn't aligned to 8" } */
+};
+
+struct __attribute__ ((packed, aligned (8))) S4 {
+  int i1;
+  int i2;
+  struct S8 s8;
+};
+
+struct __attribute__ ((packed)) S5 {
+   long long ll;
+};
+
+union __attribute__ ((packed)) U1 {
+  int i1;
+  struct S8 s8;
+}; /* { dg-warning "alignment 1 of 'union U1' is less than 8" } */
+
+union __attribute__ ((packed, aligned (8))) U2 {
+  int i1;
+  struct S8 s8;
+};
diff --git a/gcc/testsuite/gcc.dg/pr53037-3.c b/gcc/testsuite/gcc.dg/pr53037-3.c
new file mode 100644
index 0000000..fc69ae8
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr53037-3.c
@@ -0,0 +1,37 @@
+/* PR c/53037.  */
+/* { dg-do compile } */
+/* { dg-options "-O0 -Wall" } */
+
+struct __attribute__ ((aligned (8))) S8 { char a[8]; };
+struct __attribute__ ((packed)) S1 {
+  struct S8 s8;
+}; /* { dg-warning "alignment 1 of 'struct S1' is less than 8" } */
+
+struct __attribute__ ((packed, aligned (8))) S2 {
+  struct S8 s8;
+};
+
+struct __attribute__ ((packed, aligned (8))) S3 {
+  int i1;
+  struct S8 s8; /* { dg-warning "'s8' offset 4 in 'struct S3' isn't aligned to 8" } */
+};
+
+struct __attribute__ ((packed, aligned (8))) S4 {
+  int i1;
+  int i2;
+  struct S8 s8;
+};
+
+struct __attribute__ ((packed)) S5 {
+   long long ll;
+};
+
+union __attribute__ ((packed)) U1 {
+  int i1;
+  struct S8 s8;
+}; /* { dg-warning "alignment 1 of 'union U1' is less than 8" } */
+
+union __attribute__ ((packed, aligned (8))) U2 {
+  int i1;
+  struct S8 s8;
+};
diff --git a/gcc/testsuite/gcc.dg/pr53037-4.c b/gcc/testsuite/gcc.dg/pr53037-4.c
new file mode 100644
index 0000000..feb3afa
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr53037-4.c
@@ -0,0 +1,24 @@
+/* PR c/53037.  */
+/* { dg-do compile } */
+/* { dg-options "-O0" } */
+
+int foo1 __attribute__((warn_if_not_aligned(8))); /* { dg-error "'warn_if_not_aligned' may not be specified for 'foo1'" } */
+
+__attribute__((warn_if_not_aligned(8)))
+void
+foo2 (void) /* { dg-error "'warn_if_not_aligned' may not be specified for 'foo2'" } */
+{
+}
+
+struct foo3
+{
+  int i : 2 __attribute__((warn_if_not_aligned(8))); /* { dg-error "'warn_if_not_aligned' may not be specified for 'i'" } */
+};
+
+typedef unsigned int __u32
+  __attribute__((aligned(4),warn_if_not_aligned(8)));
+
+struct foo4
+{
+  __u32 i : 2; /* { dg-error "cannot declare bit-field 'i' with 'warn_if_not_aligned' type" } */
+};