re PR c++/43555 (wrong address calculation of multidimensional variable-length array element)

PR c++/43555
	* decl.c (grokdeclarator) [cdk_pointer et al]: Force evaluation of
	anonymous VLA size.

From-SVN: r159942

gcc/cp/ChangeLog

@@ -1,3 +1,9 @@
+2010-05-27  Jason Merrill  <jason@redhat.com>
+
+	PR c++/43555
+	* decl.c (grokdeclarator) [cdk_pointer et al]: Force evaluation of
+	anonymous VLA size.
+
 2010-05-19  Jason Merrill  <jason@redhat.com>
 
 	PR c++/44193

gcc/cp/decl.c

@@ -8502,6 +8502,34 @@ grokdeclarator (const cp_declarator *declarator,
 		   declarator->kind == cdk_reference ? "reference" : "pointer",
 		   type);
 
+	  /* When the pointed-to type involves components of variable size,
+	     care must be taken to ensure that the size evaluation code is
+	     emitted early enough to dominate all the possible later uses
+	     and late enough for the variables on which it depends to have
+	     been assigned.
+
+	     This is expected to happen automatically when the pointed-to
+	     type has a name/declaration of it's own, but special attention
+	     is required if the type is anonymous.
+
+	     We handle the NORMAL and FIELD contexts here by inserting a
+	     dummy statement that just evaluates the size at a safe point
+	     and ensures it is not deferred until e.g. within a deeper
+	     conditional context (c++/43555).
+
+	     We expect nothing to be needed here for PARM or TYPENAME.
+	     Evaluating the size at this point for TYPENAME would
+	     actually be incorrect, as we might be in the middle of an
+	     expression with side effects on the pointed-to type size
+	     "arguments" prior to the pointer declaration point and the
+	     size evaluation could end up prior to the side effects.  */
+
+	  if (!TYPE_NAME (type)
+	      && (decl_context == NORMAL || decl_context == FIELD)
+	      && at_function_scope_p ()
+	      && variably_modified_type_p (type, NULL_TREE))
+	    finish_expr_stmt (TYPE_SIZE (type));
+
 	  if (declarator->kind == cdk_reference)
 	    {
 	      /* In C++0x, the type we are creating a reference to might be

gcc/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2010-05-27  Jason Merrill  <jason@redhat.com>
+
+	PR c++/43555
+	* g++.dg/ext/vla9.C: New.
+
 2010-05-23  H.J. Lu  <hongjiu.lu@intel.com>
 
 	Backport from mainline

gcc/testsuite/g++.dg/ext/vla9.C

@@ -0,0 +1,38 @@
+// PR c++/43555
+// { dg-options "" }
+// { dg-do run }
+
+extern "C" void * malloc (__SIZE_TYPE__);
+extern "C" int printf (const char *, ...);
+extern "C" void abort(void);
+
+int nx,ny;
+
+void f(double *x1d,int choice)
+{
+  double (*x2d)[nx][ny]=(double(*)[nx][ny])x1d;
+  unsigned long delta;
+//  (*x2d)[0][0]=123; // <- this line affects the result
+  if (choice!=0)
+  {
+    delta=&(*x2d)[1][0]-x1d;
+  }
+  else
+  {
+    delta=&(*x2d)[1][0]-x1d;
+  }
+  printf("Choice: %d, Delta: %ld\n",choice,delta);
+  if (delta != ny)
+    abort ();
+}
+
+int main()
+{
+  double *data;
+  nx=100;
+  ny=100;
+  data=(double*)malloc(nx*ny*sizeof(double));
+  f(data,0);
+  f(data,1);
+  return 0;
+}