llvm-project/clang/test/SemaTemplate/instantiate-c99.cpp

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[c++20] Implement semantic restrictions for C++20 designated initializers. This has some interesting interactions with our existing extensions to support C99 designated initializers as an extension in C++. Those are resolved as follows: * We continue to permit the full breadth of C99 designated initializers in C++, with the exception that we disallow a partial overwrite of an initializer with a non-trivially-destructible type. (Full overwrite is OK, because we won't run the first initializer at all.) * The C99 extensions are disallowed in SFINAE contexts and during overload resolution, where they could change the meaning of valid programs. * C++20 disallows reordering of initializers. We only check for that for the simple cases that the C++20 rules permit (designators of the form '.field_name =' and continue to allow reordering in other cases). It would be nice to improve this behavior in future. * All C99 designated initializer extensions produce a warning by default in C++20 mode. People are going to learn the C++ rules based on what Clang diagnoses, so it's important we diagnose these properly by default. * In C++ <= 17, we apply the C++20 rules rather than the C99 rules, and so still diagnose C99 extensions as described above. We continue to accept designated C++20-compatible initializers in C++ <= 17 silently by default (but naturally still reject under -pedantic-errors). This is not a complete implementation of P0329R4. In particular, that paper introduces new non-C99-compatible syntax { .field { init } }, and we do not support that yet. This is based on a previous patch by Don Hinton, though I've made substantial changes when addressing the above interactions. Differential Revision: https://reviews.llvm.org/D59754 llvm-svn: 370544
2019-08-31 06:52:55 +08:00
// RUN: %clang_cc1 -Wno-c99-extensions -Wno-reorder -fsyntax-only -verify %s
// RUN: %clang_cc1 -Wno-c99-extensions -Wno-reorder -fsyntax-only -verify -std=c++98 %s
// RUN: %clang_cc1 -Wno-c99-extensions -Wno-reorder -fsyntax-only -verify -std=c++11 %s
// Test template instantiation for C99-specific features.
// ---------------------------------------------------------------------
// Designated initializers
// ---------------------------------------------------------------------
template<typename T, typename XType, typename YType>
struct DesigInit0 {
void f(XType x, YType y) {
T agg = {
#if __cplusplus <= 199711L
.y = y, // expected-error{{does not refer}}
.x = x // expected-error{{does not refer}}
#else
.y = static_cast<float>(y), // expected-error{{does not refer}}
.x = static_cast<float>(x) // expected-error{{does not refer}}
#endif
};
}
};
struct Point2D {
float x, y;
};
template struct DesigInit0<Point2D, int, double>;
struct Point3D {
float x, y, z;
};
template struct DesigInit0<Point3D, int, double>;
struct Color {
unsigned char red, green, blue;
};
struct ColorPoint3D {
Color color;
float x, y, z;
};
template struct DesigInit0<ColorPoint3D, int, double>;
template struct DesigInit0<Color, int, double>; // expected-note{{instantiation}}
template<typename T, int Subscript1, int Subscript2,
typename Val1, typename Val2>
struct DesigArrayInit0 {
void f(Val1 val1, Val2 val2) {
T array = {
#if __cplusplus <= 199711L
[Subscript1] = val1,
#else
[Subscript1] = static_cast<int>(val1),
#endif
[Subscript2] = val2 // expected-error{{exceeds array bounds}}
};
int array2[10] = { [5] = 3 };
}
};
template struct DesigArrayInit0<int[8], 5, 3, float, int>;
template struct DesigArrayInit0<int[8], 5, 13, float, int>; // expected-note{{instantiation}}
template<typename T, int Subscript1, int Subscript2,
typename Val1>
struct DesigArrayRangeInit0 {
void f(Val1 val1) {
T array = {
#if __cplusplus <= 199711L
[Subscript1...Subscript2] = val1 // expected-error{{exceeds}}
#else
[Subscript1...Subscript2] = static_cast<int>(val1) // expected-error{{exceeds}}
#endif
};
}
};
template struct DesigArrayRangeInit0<int[8], 3, 5, float>;
template struct DesigArrayRangeInit0<int[8], 5, 13, float>; // expected-note{{instantiation}}
// ---------------------------------------------------------------------
// Compound literals
// ---------------------------------------------------------------------
template<typename T, typename Arg1, typename Arg2>
struct CompoundLiteral0 {
T f(Arg1 a1, Arg2 a2) {
#if __cplusplus <= 199711L
return (T){a1, a2};
#else
return (T){static_cast<float>(a1), a2};
#endif
}
};
template struct CompoundLiteral0<Point2D, int, float>;