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If a randomized structure has an initializer with a dedicated
initializer in it, the field initialzed by that dedicated initializer
may end up at the end of the RecordDecl. This however may skip the
random layout initization check.
struct t {
int a, b, c, d, e;
} x = { .a = 2, 4, 5, 6 };
Let's say that "a" is lands as the last field after randomization. The
call to CheckDesignatedInitializer sets the iterator to the end of the
initializer list. During the next iteration of the initializer list
check, it detects that and fails to issue the error about initializing
a randomized struct with non-designated initializer. Instead, it issues
an error about "excess elements in struct initializer", which is
confusing under these circumstances.
Reviewed By: aaron.ballman
Differential Revision: https://reviews.llvm.org/D124694
78 lines
2.6 KiB
C
78 lines
2.6 KiB
C
// RUN: %clang_cc1 -triple=x86_64-unknown-linux -frandomize-layout-seed=1234567890abcded \
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// RUN: -verify -fsyntax-only -Werror %s
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// NOTE: The current seed (1234567890abcded) is specifically chosen because it
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// uncovered a bug in diagnostics. With it the randomization of "t9" places the
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// "a" element at the end of the record. When that happens, the clang complains
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// about excessive initializers, which is confusing, because there aren't
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// excessive initializers. It should instead complain about using a
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// non-designated initializer on a raqndomized struct.
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// Initializing a randomized structure requires a designated initializer,
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// otherwise the element ordering will be off. The only exceptions to this rule
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// are:
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//
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// - A structure with only one element, and
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// - A structure initialized with "{0}".
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//
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// These are well-defined situations where the field ordering doesn't affect
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// the result.
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typedef void (*func_ptr)();
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void foo(void);
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void bar(void);
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void baz(void);
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void gaz(void);
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struct test {
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func_ptr a;
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func_ptr b;
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func_ptr c;
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func_ptr d;
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func_ptr e;
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func_ptr f;
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func_ptr g;
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} __attribute__((randomize_layout));
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struct test t1 = {}; // This should be fine per WG14 N2900 (in C23) + our extension handling of it in earlier modes
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struct test t2 = { 0 }; // This should also be fine per C99 6.7.8p19
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struct test t3 = { .f = baz, .b = bar, .g = gaz, .a = foo }; // Okay
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struct test t4 = { .a = foo, bar, baz }; // expected-error {{a randomized struct can only be initialized with a designated initializer}}
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struct other_test {
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func_ptr a;
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func_ptr b[3];
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func_ptr c;
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} __attribute__((randomize_layout));
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struct other_test t5 = { .a = foo, .b[0] = foo }; // Okay
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struct other_test t6 = { .a = foo, .b[0] = foo, bar, baz }; // Okay
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struct other_test t7 = { .a = foo, .b = { foo, bar, baz } }; // Okay
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struct other_test t8 = { baz, bar, gaz, foo }; // expected-error {{a randomized struct can only be initialized with a designated initializer}}
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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}}
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struct empty_test {
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} __attribute__((randomize_layout));
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struct empty_test t10 = {}; // Okay
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struct degen_test {
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func_ptr a;
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} __attribute__((randomize_layout));
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struct degen_test t11 = { foo }; // Okay
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struct static_assert_test {
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int f;
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_Static_assert(sizeof(int) == 4, "oh no!");
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} __attribute__((randomize_layout));
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struct static_assert_test t12 = { 42 }; // Okay
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struct enum_decl_test {
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enum e { BORK = 42, FORK = 9 } f;
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} __attribute__((randomize_layout));
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struct enum_decl_test t13 = { BORK }; // Okay
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