2017-09-15 Bernd Edlinger <bernd.edlinger@hotmail.de>

        * common.opt (Wcast-align=strict): New warning option.
        * doc/invoke.texi: Document -Wcast-align=strict.

c:
2017-09-15  Bernd Edlinger  <bernd.edlinger@hotmail.de>

        * c-typeck.c (build_c_cast): Implement -Wcast-align=strict.

cp:
2017-09-15  Bernd Edlinger  <bernd.edlinger@hotmail.de>

        * typeck.c (build_reinterpret_cast_1,
        build_const_cast_1): Implement -Wcast-align=strict.

testsuite:
2017-09-15  Bernd Edlinger  <bernd.edlinger@hotmail.de>

        * c-c++-common/Wcast-align.c: New test.


git-svn-id: https://gcc.gnu.org/svn/gcc/trunk@252832 138bc75d-0d04-0410-961f-82ee72b054a4

9 files changed, 69 insertions, 7 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index b3d3407f171..050aef81445 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2017-09-15  Bernd Edlinger  <bernd.edlinger@hotmail.de>
+
+	* common.opt (Wcast-align=strict): New warning option.
+	* doc/invoke.texi: Document -Wcast-align=strict. 
+
 2017-09-15  Pierre-Marie de Rodat  <derodat@adacore.com>
 
 	* cgraph.h (cgraph_thunk_info): Add comments.
diff --git a/gcc/c/ChangeLog b/gcc/c/ChangeLog
index 957daeb4fe9..e8e0fb087d3 100644
--- a/gcc/c/ChangeLog
+++ b/gcc/c/ChangeLog
@@ -1,3 +1,7 @@
+2017-09-15  Bernd Edlinger  <bernd.edlinger@hotmail.de>
+
+	* c-typeck.c (build_c_cast): Implement -Wcast-align=strict.
+
 2017-09-13  Marek Polacek  <polacek@redhat.com>
 
 	PR c/82167
diff --git a/gcc/c/c-typeck.c b/gcc/c/c-typeck.c
index f45fd3cfbbf..1956d45e251 100644
--- a/gcc/c/c-typeck.c
+++ b/gcc/c/c-typeck.c
@@ -5578,7 +5578,7 @@ build_c_cast (location_t loc, tree type, tree expr)
 	}
 
       /* Warn about possible alignment problems.  */
-      if (STRICT_ALIGNMENT
+      if ((STRICT_ALIGNMENT || warn_cast_align == 2)
 	  && TREE_CODE (type) == POINTER_TYPE
 	  && TREE_CODE (otype) == POINTER_TYPE
 	  && TREE_CODE (TREE_TYPE (otype)) != VOID_TYPE
@@ -5587,7 +5587,8 @@ build_c_cast (location_t loc, tree type, tree expr)
 	     restriction is unknown.  */
 	  && !(RECORD_OR_UNION_TYPE_P (TREE_TYPE (otype))
 	       && TYPE_MODE (TREE_TYPE (otype)) == VOIDmode)
-	  && TYPE_ALIGN (TREE_TYPE (type)) > TYPE_ALIGN (TREE_TYPE (otype)))
+	  && min_align_of_type (TREE_TYPE (type))
+	     > min_align_of_type (TREE_TYPE (otype)))
 	warning_at (loc, OPT_Wcast_align,
 		    "cast increases required alignment of target type");
 
diff --git a/gcc/common.opt b/gcc/common.opt
index 1581ca885e5..fa6dd845d54 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -566,6 +566,10 @@ Wcast-align
 Common Var(warn_cast_align) Warning
 Warn about pointer casts which increase alignment.
 
+Wcast-align=strict
+Common Var(warn_cast_align,2) Warning
+Warn about pointer casts which increase alignment.
+
 Wcpp
 Common Var(warn_cpp) Init(1) Warning
 Warn when a #warning directive is encountered.
diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 0a3b80f4518..c0132251edc 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,8 @@
+2017-09-15  Bernd Edlinger  <bernd.edlinger@hotmail.de>
+
+	* typeck.c (build_reinterpret_cast_1,
+	build_const_cast_1): Implement -Wcast-align=strict.
+
 2017-09-15  Jakub Jelinek  <jakub@redhat.com>
 
 	* decl.c (redeclaration_error_message): Use cxx17 instead of cxx1z,
diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c
index aa5d1288a5a..028d56ff18c 100644
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@@ -7265,15 +7265,16 @@ build_reinterpret_cast_1 (tree type, tree expr, bool c_cast_p,
 					       complain))
 	return error_mark_node;
       /* Warn about possible alignment problems.  */
-      if (STRICT_ALIGNMENT && warn_cast_align
-          && (complain & tf_warning)
+      if ((STRICT_ALIGNMENT || warn_cast_align == 2)
+	  && (complain & tf_warning)
 	  && !VOID_TYPE_P (type)
 	  && TREE_CODE (TREE_TYPE (intype)) != FUNCTION_TYPE
 	  && COMPLETE_TYPE_P (TREE_TYPE (type))
 	  && COMPLETE_TYPE_P (TREE_TYPE (intype))
-	  && TYPE_ALIGN (TREE_TYPE (type)) > TYPE_ALIGN (TREE_TYPE (intype)))
+	  && min_align_of_type (TREE_TYPE (type))
+	     > min_align_of_type (TREE_TYPE (intype)))
 	warning (OPT_Wcast_align, "cast from %qH to %qI "
-                 "increases required alignment of target type", intype, type);
+		 "increases required alignment of target type", intype, type);
 
       /* We need to strip nops here, because the front end likes to
 	 create (int *)&a for array-to-pointer decay, instead of &a[0].  */
@@ -7447,6 +7448,14 @@ build_const_cast_1 (tree dst_type, tree expr, tsubst_flags_t complain,
 		 the user is making a potentially unsafe cast.  */
 	      check_for_casting_away_constness (src_type, dst_type,
 						CAST_EXPR, complain);
+	      /* ??? comp_ptr_ttypes_const ignores TYPE_ALIGN.  */
+	      if ((STRICT_ALIGNMENT || warn_cast_align == 2)
+		  && (complain & tf_warning)
+		  && min_align_of_type (TREE_TYPE (dst_type))
+		     > min_align_of_type (TREE_TYPE (src_type)))
+		warning (OPT_Wcast_align, "cast from %qH to %qI "
+			 "increases required alignment of target type",
+			 src_type, dst_type);
 	    }
 	  if (reference_type)
 	    {
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index a727d952fd2..60650c83917 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -266,7 +266,8 @@ Objective-C and Objective-C++ Dialects}.
 -Wno-attributes  -Wbool-compare  -Wbool-operation @gol
 -Wno-builtin-declaration-mismatch @gol
 -Wno-builtin-macro-redefined  -Wc90-c99-compat  -Wc99-c11-compat @gol
--Wc++-compat  -Wc++11-compat  -Wc++14-compat  -Wcast-align  -Wcast-qual  @gol
+-Wc++-compat  -Wc++11-compat  -Wc++14-compat  @gol
+-Wcast-align  -Wcast-align=strict  -Wcast-qual  @gol
 -Wchar-subscripts  -Wchkp  -Wcatch-value  -Wcatch-value=@var{n} @gol
 -Wclobbered  -Wcomment  -Wconditionally-supported @gol
 -Wconversion  -Wcoverage-mismatch  -Wno-cpp  -Wdangling-else  -Wdate-time @gol
@@ -5931,6 +5932,12 @@ target is increased.  For example, warn if a @code{char *} is cast to
 an @code{int *} on machines where integers can only be accessed at
 two- or four-byte boundaries.
 
+@item -Wcast-align=strict
+@opindex Wcast-align=strict
+Warn whenever a pointer is cast such that the required alignment of the
+target is increased.  For example, warn if a @code{char *} is cast to
+an @code{int *} regardless of the target machine.
+
 @item -Wwrite-strings
 @opindex Wwrite-strings
 @opindex Wno-write-strings
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 303f700c451..0091855e2c9 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2017-09-15  Bernd Edlinger  <bernd.edlinger@hotmail.de>
+
+	* c-c++-common/Wcast-align.c: New test.
+
 2017-09-15  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* g++.dg/sso-1.C: New test.
diff --git a/gcc/testsuite/c-c++-common/Wcast-align.c b/gcc/testsuite/c-c++-common/Wcast-align.c
new file mode 100644
index 00000000000..fac1795476c
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/Wcast-align.c
@@ -0,0 +1,23 @@
+/* { dg-do compile } */
+/* { dg-options "-Wcast-align=strict" } */
+
+typedef char __attribute__ ((__aligned__(__BIGGEST_ALIGNMENT__))) c;
+typedef struct __attribute__ ((__aligned__(__BIGGEST_ALIGNMENT__)))
+{
+  char x;
+} d;
+
+char *x;
+c *y;
+d *z;
+struct s { long long x; } *p;
+struct t { double x; } *q;
+
+void
+foo (void)
+{
+  y = (c *) x;  /* { dg-warning "alignment" } */
+  z = (d *) x;  /* { dg-warning "alignment" } */
+  (long long *) p;  /* { dg-bogus "alignment" } */
+  (double *) q;     /* { dg-bogus "alignment" } */
+}