7955bde64e
This is about the best I could do for testing that `signed char` does not have any padding bits.
32 lines
1.2 KiB
C
32 lines
1.2 KiB
C
// RUN: %clang_cc1 -verify -std=c89 %s
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// RUN: %clang_cc1 -verify -std=c99 %s
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// RUN: %clang_cc1 -verify -std=c11 %s
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// RUN: %clang_cc1 -verify -std=c17 %s
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// RUN: %clang_cc1 -verify -std=c23 %s
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// expected-no-diagnostics
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/* WG14 N1310: Yes
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* Requiring signed char to have no padding bits
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*/
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/* This is shockingly hard to test, but we're trying our best by checking that
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* setting each bit of an unsigned char, then bit-casting it to signed char,
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* results in a value we expect to see. If we have padding bits, then it's
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* possible (but not mandatory) for the value to not be as we expect, so a
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* failing assertion means the implementation is broken but a passing test does
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* not *prove* there aren't padding bits.
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*/
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_Static_assert(__CHAR_BIT__ == 8, "");
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_Static_assert(sizeof(signed char) == 1, "");
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#define TEST(Bit, Expected) __builtin_bit_cast(signed char, (unsigned char)(1 << Bit)) == Expected
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_Static_assert(TEST(0, 1), "");
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_Static_assert(TEST(1, 2), "");
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_Static_assert(TEST(2, 4), "");
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_Static_assert(TEST(3, 8), "");
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_Static_assert(TEST(4, 16), "");
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_Static_assert(TEST(5, 32), "");
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_Static_assert(TEST(6, 64), "");
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_Static_assert(TEST(7, (signed char)128), "");
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