c-common.c (check_user_alignment): Emit error for negative values.

c-family:
2013-04-03  Senthil Kumar Selvaraj  <senthil_kumar.selvaraj@atmel.com>

	* c-common.c (check_user_alignment): Emit error for negative values.

testsuite:
2013-04-03  Senthil Kumar Selvaraj  <senthil_kumar.selvaraj@atmel.com>

	* gcc.dg/c1x-align-3.c: Add test for negative power of 2.

From-SVN: r198417

gcc/c-family/ChangeLog

+2013-04-29  Senthil Kumar Selvaraj  <senthil_kumar.selvaraj@atmel.com>
+
+	* c-common.c (check_user_alignment): Emit error for negative values.
+
 2013-04-24  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	* c-opts.c (set_std_cxx11): Use CLK_CXX1Y and CLK_GNUCXX1Y.

gcc/c-family/c-common.c

@@ -7302,9 +7302,10 @@ check_user_alignment (const_tree align, bool allow_zero)
     }
   else if (allow_zero && integer_zerop (align))
     return -1;
-  else if ((i = tree_log2 (align)) == -1)
+  else if (tree_int_cst_sgn (align) == -1
+           || (i = tree_log2 (align)) == -1)
     {
-      error ("requested alignment is not a power of 2");
+      error ("requested alignment is not a positive power of 2");
       return -1;
     }
   else if (i >= HOST_BITS_PER_INT - BITS_PER_UNIT_LOG)

gcc/testsuite/ChangeLog

+2013-04-29  Senthil Kumar Selvaraj  <senthil_kumar.selvaraj@atmel.com>
+
+	* gcc.dg/c1x-align-3.c: Add test for negative power of 2.
+
 2013-04-29  Tom de Vries  <tom@codesourcery.com>
 
 	* gcc.dg/pr50763.c: Update test.

gcc/testsuite/gcc.dg/c1x-align-3.c

@@ -23,6 +23,7 @@ _Alignas (-(__LONG_LONG_MAX__-1)/4) char i3; /* { dg-error "too large|power of 2
 _Alignas (-(__LONG_LONG_MAX__-1)/8) char i4; /* { dg-error "too large|power of 2" } */
 _Alignas (-(__LONG_LONG_MAX__-1)/16) char i5; /* { dg-error "too large|power of 2" } */
 _Alignas (-1) char j; /* { dg-error "power of 2" } */
+_Alignas (-2) char j; /* { dg-error "positive power of 2" } */
 _Alignas (3) char k; /* { dg-error "power of 2" } */
 
 _Alignas ((void *) 1) char k; /* { dg-error "integer constant" } */