clang/test/Sema/init-randomized-struct.c

   1 // RUN: %clang_cc1 -triple=x86_64-unknown-linux -frandomize-layout-seed=1234567890abcded \
   2 // RUN:  -verify -fsyntax-only -Werror %s
   3
   4 // NOTE: The current seed (1234567890abcded) is specifically chosen because it
   5 // uncovered a bug in diagnostics. With it the randomization of "t9" places the
   6 // "a" element at the end of the record. When that happens, the clang complains
   7 // about excessive initializers, which is confusing, because there aren't
   8 // excessive initializers. It should instead complain about using a
   9 // non-designated initializer on a raqndomized struct.
  10
  11 // Initializing a randomized structure requires a designated initializer,
  12 // otherwise the element ordering will be off. The only exceptions to this rule
  13 // are:
  14 //
  15 //    - A structure with only one element, and
  16 //    - A structure initialized with "{0}".
  17 //
  18 // These are well-defined situations where the field ordering doesn't affect
  19 // the result.
  20
  21 typedef void (*func_ptr)();
  22
  23 void foo(void);
  24 void bar(void);
  25 void baz(void);
  26 void gaz(void);
  27
  28 struct test {
  29   func_ptr a;
  30   func_ptr b;
  31   func_ptr c;
  32   func_ptr d;
  33   func_ptr e;
  34   func_ptr f;
  35   func_ptr g;
  36 } __attribute__((randomize_layout));
  37
  38 struct test t1 = {}; // This should be fine per WG14 N2900 (in C23) + our extension handling of it in earlier modes
  39 struct test t2 = { 0 }; // This should also be fine per C99 6.7.8p19
  40 struct test t3 = { .f = baz, .b = bar, .g = gaz, .a = foo }; // Okay
  41 struct test t4 = { .a = foo, bar, baz }; // expected-error {{a randomized struct can only be initialized with a designated initializer}}
  42
  43 struct other_test {
  44   func_ptr a;
  45   func_ptr b[3];
  46   func_ptr c;
  47 } __attribute__((randomize_layout));
  48
  49 struct other_test t5 = { .a = foo, .b[0] = foo }; // Okay
  50 struct other_test t6 = { .a = foo, .b[0] = foo, bar, baz }; // Okay
  51 struct other_test t7 = { .a = foo, .b = { foo, bar, baz } }; // Okay
  52 struct other_test t8 = { baz, bar, gaz, foo }; // expected-error {{a randomized struct can only be initialized with a designated initializer}}
  53 struct other_test t9 = { .a = foo, .b[0] = foo, bar, baz, gaz }; // expected-error {{a randomized struct can only be initialized with a designated initializer}}
  54
  55 struct empty_test {
  56 } __attribute__((randomize_layout));
  57
  58 struct empty_test t10 = {}; // Okay
  59
  60 struct degen_test {
  61   func_ptr a;
  62 } __attribute__((randomize_layout));
  63
  64 struct degen_test t11 = { foo }; // Okay
  65
  66 struct static_assert_test {
  67   int f;
  68   _Static_assert(sizeof(int) == 4, "oh no!");
  69 } __attribute__((randomize_layout));
  70
  71 struct static_assert_test t12 = { 42 }; // Okay
  72
  73 struct enum_decl_test {
  74   enum e { BORK = 42, FORK = 9 } f;
  75 } __attribute__((randomize_layout));
  76
  77 struct enum_decl_test t13 = { BORK }; // Okay