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WG14 adopted N2775 (http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2775.pdf) at our Feb 2022 meeting. This paper adds a literal suffix for bit-precise types that automatically sizes the bit-precise type to be the smallest possible legal _BitInt type that can represent the literal value. The suffix chosen is wb (for a signed bit-precise type) which can be combined with the u suffix (for an unsigned bit-precise type). The preprocessor continues to operate as-if all integer types were intmax_t/uintmax_t, including bit-precise integer types. It is a constraint violation if the bit-precise literal is too large to fit within that type in the context of the preprocessor (when still using a pp-number preprocessing token), but it is not a constraint violation in other circumstances. This allows you to make bit-precise integer literals that are wider than what the preprocessor currently supports in order to initialize variables, etc.
48 lines
2.7 KiB
C
48 lines
2.7 KiB
C
// RUN: %clang_cc1 -std=c2x -ast-dump -Wno-unused %s | FileCheck --strict-whitespace %s
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// CHECK: FunctionDecl 0x{{[^ ]*}} <{{.*}}:[[@LINE+1]]:1, line:{{[0-9]*}}:1> line:[[@LINE+1]]:6 func 'void (void)'
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void func(void) {
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// Ensure that we calculate the correct type from the literal suffix.
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// Note: 0wb should create an _BitInt(2) because a signed bit-precise
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// integer requires one bit for the sign and one bit for the value,
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// at a minimum.
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// CHECK: TypedefDecl 0x{{[^ ]*}} <col:3, col:27> col:27 zero_wb 'typeof (0wb)':'_BitInt(2)'
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typedef __typeof__(0wb) zero_wb;
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// CHECK: TypedefDecl 0x{{[^ ]*}} <col:3, col:28> col:28 neg_zero_wb 'typeof (-0wb)':'_BitInt(2)'
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typedef __typeof__(-0wb) neg_zero_wb;
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// CHECK: TypedefDecl 0x{{[^ ]*}} <col:3, col:27> col:27 one_wb 'typeof (1wb)':'_BitInt(2)'
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typedef __typeof__(1wb) one_wb;
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// CHECK: TypedefDecl 0x{{[^ ]*}} <col:3, col:28> col:28 neg_one_wb 'typeof (-1wb)':'_BitInt(2)'
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typedef __typeof__(-1wb) neg_one_wb;
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// CHECK: TypedefDecl 0x{{[^ ]*}} <col:3, col:28> col:28 zero_uwb 'typeof (0uwb)':'unsigned _BitInt(1)'
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typedef __typeof__(0uwb) zero_uwb;
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// CHECK: TypedefDecl 0x{{[^ ]*}} <col:3, col:29> col:29 neg_zero_uwb 'typeof (-0uwb)':'unsigned _BitInt(1)'
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typedef __typeof__(-0uwb) neg_zero_uwb;
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// CHECK: TypedefDecl 0x{{[^ ]*}} <col:3, col:28> col:28 one_uwb 'typeof (1uwb)':'unsigned _BitInt(1)'
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typedef __typeof__(1uwb) one_uwb;
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// Try a value that is too large to fit in [u]intmax_t.
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// CHECK: TypedefDecl 0x{{[^ ]*}} <col:3, col:47> col:47 huge_uwb 'typeof (18446744073709551616uwb)':'unsigned _BitInt(65)'
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typedef __typeof__(18446744073709551616uwb) huge_uwb;
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// CHECK: TypedefDecl 0x{{[^ ]*}} <col:3, col:46> col:46 huge_wb 'typeof (18446744073709551616wb)':'_BitInt(66)'
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typedef __typeof__(18446744073709551616wb) huge_wb;
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}
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// Test the examples from the paper.
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// CHECK: FunctionDecl 0x{{[^ ]*}} <{{.*}}:[[@LINE+1]]:1, line:{{[0-9]*}}:1> line:[[@LINE+1]]:6 from_paper 'void (void)'
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void from_paper(void) {
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// CHECK: TypedefDecl 0x{{[^ ]*}} <col:3, col:28> col:28 neg_three_wb 'typeof (-3wb)':'_BitInt(3)'
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typedef __typeof__(-3wb) neg_three_wb;
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// CHECK: TypedefDecl 0x{{[^ ]*}} <col:3, col:30> col:30 neg_three_hex_wb 'typeof (-3wb)':'_BitInt(3)'
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typedef __typeof__(-0x3wb) neg_three_hex_wb;
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// CHECK: TypedefDecl 0x{{[^ ]*}} <col:3, col:27> col:27 three_wb 'typeof (3wb)':'_BitInt(3)'
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typedef __typeof__(3wb) three_wb;
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// CHECK: TypedefDecl 0x{{[^ ]*}} <col:3, col:28> col:28 three_uwb 'typeof (3uwb)':'unsigned _BitInt(2)'
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typedef __typeof__(3uwb) three_uwb;
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// CHECK: TypedefDecl 0x{{[^ ]*}} <col:3, col:29> col:29 neg_three_uwb 'typeof (-3uwb)':'unsigned _BitInt(2)'
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typedef __typeof__(-3uwb) neg_three_uwb;
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}
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