re PR c/67882 (surprising offsetof result on an invalid array member without diagnostic)

PR c++-common/67882

	* c-family/c-common.h (fold_offsetof_1): Add argument.
	* c-family/c-common.c (fold_offsetof_1): Diagnose more invalid
	offsetof expressions that reference elements past the end of
	an array.

        * c-c++-common/builtin-offsetof-2.c: New test.

From-SVN: r229717

gcc/c-family/ChangeLog

+2015-11-03  Bernd Schmidt <bschmidt@redhat.com>
+
+	PR c++-common/67882
+	* c-family/c-common.h (fold_offsetof_1): Add argument.
+	* c-family/c-common.c (fold_offsetof_1): Diagnose more invalid
+	offsetof expressions that reference elements past the end of
+	an array.
+
 2015-11-03  Thomas Schwinge  <thomas@codesourcery.com>
 	    Chung-Lin Tang  <cltang@codesourcery.com>
 

gcc/c-family/c-common.c

@@ -10631,11 +10631,11 @@ c_common_to_target_charset (HOST_WIDE_INT c)
    traditional rendering of offsetof as a macro.  Return the folded result.  */
 
 tree
-fold_offsetof_1 (tree expr)
+fold_offsetof_1 (tree expr, enum tree_code ctx)
 {
   tree base, off, t;
-
-  switch (TREE_CODE (expr))
+  tree_code code = TREE_CODE (expr);
+  switch (code)
     {
     case ERROR_MARK:
       return expr;
@@ -10659,7 +10659,7 @@ fold_offsetof_1 (tree expr)
       return TREE_OPERAND (expr, 0);
 
     case COMPONENT_REF:
-      base = fold_offsetof_1 (TREE_OPERAND (expr, 0));
+      base = fold_offsetof_1 (TREE_OPERAND (expr, 0), code);
       if (base == error_mark_node)
 	return base;
 
@@ -10676,7 +10676,7 @@ fold_offsetof_1 (tree expr)
       break;
 
     case ARRAY_REF:
-      base = fold_offsetof_1 (TREE_OPERAND (expr, 0));
+      base = fold_offsetof_1 (TREE_OPERAND (expr, 0), code);
       if (base == error_mark_node)
 	return base;
 
@@ -10691,8 +10691,9 @@ fold_offsetof_1 (tree expr)
 	      && !tree_int_cst_equal (upbound,
 				      TYPE_MAX_VALUE (TREE_TYPE (upbound))))
 	    {
-	      upbound = size_binop (PLUS_EXPR, upbound,
-				    build_int_cst (TREE_TYPE (upbound), 1));
+	      if (ctx != ARRAY_REF && ctx != COMPONENT_REF)
+	        upbound = size_binop (PLUS_EXPR, upbound,
+				      build_int_cst (TREE_TYPE (upbound), 1));
 	      if (tree_int_cst_lt (upbound, t))
 		{
 		  tree v;

gcc/c-family/c-common.h

@@ -1029,7 +1029,7 @@ extern bool c_dump_tree (void *, tree);
 
 extern void verify_sequence_points (tree);
 
-extern tree fold_offsetof_1 (tree);
+extern tree fold_offsetof_1 (tree, tree_code ctx = ERROR_MARK);
 extern tree fold_offsetof (tree);
 
 /* Places where an lvalue, or modifiable lvalue, may be required.

gcc/testsuite/ChangeLog

+2015-11-03  Martin Sebor  <msebor@redhat.com>
+
+	PR c++-common/67882
+	* c-c++-common/builtin-offsetof-2.c: New test.
+
 2015-11-03  Dominique d'Humieres <dominiq@lps.ens.fr>
 
 	PR fortran/67982

gcc/testsuite/c-c++-common/builtin-offsetof-2.c

+// { dg-options "-Warray-bounds" }
+// { dg-do compile }
+
+// Test case exercising pr c/67882 - surprising offsetof result
+//   on an invalid array member without diagnostic.
+
+typedef struct A1 {
+  char a1[1];
+  char c;
+} A1;
+
+typedef struct A1_x_2 {
+  char a1[1];
+  char a[][2];
+} A1_x_2;
+
+typedef struct A1_1_x {
+  char a1_1[1][1];
+  char a[];
+} A1_1_x;
+
+typedef struct Ax_2_3 {
+  int i;
+  char a_x_2_3[][2][3];
+} Ax_2_3;
+
+typedef struct A1_1 {
+  char a1_1[1][1];
+  char c;
+} A1_1;
+
+typedef struct B {
+  A1_1 a2_3[2][3];
+  char a1_1[3][5];
+  char a[];
+} B;
+
+// Structures with members that contain flexible array members are
+// an extension accepted by GCC.
+typedef struct C {
+  A1_1_x a5_7 [5][7];
+  int a;
+} C;
+
+// Structs with a "fake" flexible array member (a GCC extension).
+typedef struct FA0 {
+  int i;
+  char a0 [0];
+} FA0;
+
+typedef struct FA1 {
+  int i;
+  char a1 [1];
+} FA1;
+
+typedef struct FA3 {
+  int i;
+  char a3 [3];
+} FA3;
+
+// A "fake" multidimensional flexible array member.
+typedef struct FA5_7 {
+  int i;
+  char a5_7 [5][7];
+} FA5_7;
+
+static void test (void)
+{
+  // Verify that offsetof references to array elements past the end of
+  // the array member are diagnosed.  As an extension, permit references
+  // to the element just past-the-end of the array.
+
+  int a[] = {
+    __builtin_offsetof (A1, a1),                 // valid
+    __builtin_offsetof (A1, a1 [0]),             // valid
+
+    // The following expression is valid because it forms the equivalent
+    // of an address pointing just past the last element of the array.
+    __builtin_offsetof (A1, a1 [1]),             // valid
+
+    __builtin_offsetof (A1, a1 [2]),             // { dg-warning "index" }
+
+    __builtin_offsetof (A1_x_2, a1),             // valid
+    __builtin_offsetof (A1_x_2, a1 [0]),         // valid
+    __builtin_offsetof (A1_x_2, a1 [1]),         // valid
+    __builtin_offsetof (A1_x_2, a1 [2]),         // { dg-warning "index" }
+
+    __builtin_offsetof (A1_x_2, a),              // valid
+    __builtin_offsetof (A1_x_2, a [0]),          // valid
+    __builtin_offsetof (A1_x_2, a [1]),          // valid
+    __builtin_offsetof (A1_x_2, a [99]),         // valid
+
+    __builtin_offsetof (A1_x_2, a),              // valid
+    __builtin_offsetof (A1_x_2, a [0][0]),       // valid
+    __builtin_offsetof (A1_x_2, a [0][1]),       // valid
+
+    // The following expression is valid because it forms the equivalent
+    // of an address pointing just past the last element of the first
+    // array.
+    __builtin_offsetof (A1_x_2, a [0][2]),       // valid
+
+    // Unlike the case above, this is invalid since it refers to an element
+    // past one one just-past-the-end in A[][2].
+    __builtin_offsetof (A1_x_2, a [0][3]),       // { dg-warning "index" }
+
+    __builtin_offsetof (A1_x_2, a [1][0]),       // valid
+    __builtin_offsetof (A1_x_2, a [1][1]),       // valid
+    __builtin_offsetof (A1_x_2, a [1][2]),       // valid
+    __builtin_offsetof (A1_x_2, a [99][0]),      // valid
+    __builtin_offsetof (A1_x_2, a [99][1]),      // valid
+    __builtin_offsetof (A1_x_2, a [99][2]),      // valid
+
+    __builtin_offsetof (A1_1_x, a),              // valid
+    __builtin_offsetof (A1_1_x, a [0]),          // valid
+    __builtin_offsetof (A1_1_x, a [1]),          // valid
+    __builtin_offsetof (A1_1_x, a [99]),         // valid
+
+    __builtin_offsetof (A1_1_x, a1_1 [0][0]),    // valid
+    __builtin_offsetof (A1_1_x, a1_1 [0][1]),    // valid
+    __builtin_offsetof (A1_1_x, a1_1 [0][2]),    // { dg-warning "index" }
+    __builtin_offsetof (A1_1_x, a1_1 [1][0]),    // { dg-warning "index" }
+    __builtin_offsetof (A1_1_x, a1_1 [1][1]),    // { dg-warning "index" }
+
+    __builtin_offsetof (Ax_2_3, a_x_2_3 [0][1][3]),  // valid
+    __builtin_offsetof (Ax_2_3, a_x_2_3 [0][1][4]),  // { dg-warning "index" }
+    __builtin_offsetof (Ax_2_3, a_x_2_3 [0][2]),     // valid
+    __builtin_offsetof (Ax_2_3, a_x_2_3 [0][2][0]),  // { dg-warning "index" }
+
+    __builtin_offsetof (B, a2_3 [0][0].c),           // valid
+    __builtin_offsetof (B, a2_3 [0][0].a1_1 [0][0]), // valid
+    __builtin_offsetof (B, a2_3 [1][3]),             // valid
+    __builtin_offsetof (B, a2_3 [1][4]),             // { dg-warning "index" }
+    __builtin_offsetof (B, a2_3 [0][0].a1_1 [0][1]), // valid
+    __builtin_offsetof (B, a2_3 [0][0].a1_1 [0][2]), // { dg-warning "index" }
+
+    __builtin_offsetof (B, a2_3 [0][0].a1_1 [1][0]), // { dg-warning "index" }
+    __builtin_offsetof (B, a2_3 [0][0].a1_1 [1][1]), // { dg-warning "index" }
+
+    __builtin_offsetof (B, a2_3 [1][2].a1_1 [0][0]), // valid
+
+    // Forming an offset to the just-past-end element is valid.
+    __builtin_offsetof (B, a2_3 [1][2].a1_1 [0][1]), // valid
+    __builtin_offsetof (B, a2_3 [1][2].a1_1 [1][0]), // { dg-warning "index" }
+    __builtin_offsetof (B, a2_3 [1][2].a1_1 [1][1]), // { dg-warning "index" }
+
+    // Forming an offset to the just-past-end element is valid.
+    __builtin_offsetof (B, a2_3 [1][3]),             // valid
+    // ...but these are diagnosed because they dereference a just-past-the-end
+    // element.
+    __builtin_offsetof (B, a2_3 [1][3].a1_1 [0][0]), // { dg-warning "index" }
+    __builtin_offsetof (B, a2_3 [1][3].a1_1 [0][0]), // { dg-warning "index" }
+    __builtin_offsetof (B, a2_3 [1][3].a1_1 [0][1]), // { dg-warning "index" }
+    __builtin_offsetof (B, a2_3 [1][3].a1_1 [1][0]), // { dg-warning "index" }
+    __builtin_offsetof (B, a2_3 [1][3].a1_1 [1][1]), // { dg-warning "index" }
+
+    // Analogous to the case above, these are both diagnosed because they
+    // dereference just-past-the-end elements of the a2_3 array.
+    __builtin_offsetof (B, a2_3 [1][3].c),       // { dg-warning "index" }
+    __builtin_offsetof (B, a2_3 [1][3].c),       // { dg-warning "index" }
+
+    // The following are all invalid because of the reference to a2_3[2].
+    __builtin_offsetof (B, a2_3 [2][0].a1_1 [0][0]), // { dg-warning "index" }
+    __builtin_offsetof (B, a2_3 [2][0].a1_1 [0][1]), // { dg-warning "index" }
+    __builtin_offsetof (B, a2_3 [2][0].a1_1 [1][0]), // { dg-warning "index" }
+    __builtin_offsetof (B, a2_3 [2][0].a1_1 [1][1]), // { dg-warning "index" }
+    __builtin_offsetof (B, a2_3 [2][0].c),           // { dg-warning "index" }
+
+    __builtin_offsetof (C, a5_7 [4][6]),
+    __builtin_offsetof (C, a5_7 [4][6].a),
+    __builtin_offsetof (C, a5_7 [4][6].a [0]),
+    __builtin_offsetof (C, a5_7 [4][6].a [99]),
+
+    __builtin_offsetof (C, a5_7 [4][7]),             // valid
+    // Diagnose the following even though the object whose offset is
+    // computed is a flexible array member.
+    __builtin_offsetof (C, a5_7 [4][7].a),           // { dg-warning "index" }
+    __builtin_offsetof (C, a5_7 [4][7].a [0]),       // { dg-warning "index" }
+    __builtin_offsetof (C, a5_7 [4][7].a [99]),      // { dg-warning "index" }
+
+    // Verify that no diagnostic is issued for offsetof expressions
+    // involving structs where the array has a rank of 1 and is the last
+    // member (e.g., those are treated as flexible array members).
+    __builtin_offsetof (FA0, a0 [0]),
+    __builtin_offsetof (FA0, a0 [1]),
+    __builtin_offsetof (FA0, a0 [99]),
+
+    __builtin_offsetof (FA1, a1 [0]),
+    __builtin_offsetof (FA1, a1 [1]),
+    __builtin_offsetof (FA1, a1 [99]),
+
+    __builtin_offsetof (FA3, a3 [0]),
+    __builtin_offsetof (FA3, a3 [3]),
+    __builtin_offsetof (FA3, a3 [99]),
+
+    __builtin_offsetof (FA5_7, a5_7 [0][0]),
+
+    // Unlike one-dimensional arrays, verify that out-of-bounds references
+    // to "fake" flexible arrays with rank of 2 and greater are diagnosed.
+
+    // The following are valid because they compute the offset of just past
+    // the end of each of the a5_7[0] and a5_7[1] arrays.
+    __builtin_offsetof (FA5_7, a5_7 [0][7]),         // valid
+    __builtin_offsetof (FA5_7, a5_7 [1][7]),         // valid
+
+    // The following two are accepted as an extesion (because a5_7 is
+    // treated as a flexible array member).
+    __builtin_offsetof (FA5_7, a5_7 [5][0]),         // extension
+    __builtin_offsetof (FA5_7, a5_7 [5][7]),         // extension
+
+    // The following are invalid since in both cases they denote an element
+    // that's beyond just-past-the-end of the array.
+    __builtin_offsetof (FA5_7, a5_7 [0][8]),        // { dg-warning "index" }
+    __builtin_offsetof (FA5_7, a5_7 [6][8])         // { dg-warning "index" }
+  };
+
+  (void)&a;
+}