5030928d60
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
57 lines
1.2 KiB
C++
57 lines
1.2 KiB
C++
// RUN: %clang_cc1 -std=c++1z -verify %s
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namespace pr32864_0 {
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struct transfer_t {
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void *fctx;
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};
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template <typename Ctx> class record {
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void run() {
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transfer_t t;
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Ctx from{t.fctx};
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}
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};
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}
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namespace pr33140_0a {
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struct S {
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constexpr S(const int &a = 0) {}
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};
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void foo(void) { S s[2] = {}; }
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}
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namespace pr33140_0b {
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bool bar(float const &f = 0);
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bool foo() { return bar() && bar(); }
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}
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namespace pr33140_2 {
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// FIXME: The declaration of 'b' below should lifetime-extend two int
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// temporaries.
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struct A { int &&r = 0; }; // expected-note 2{{initializing field 'r' with default member initializer}}
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struct B { A x, y; };
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B b = {}; // expected-warning 2{{not supported}}
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}
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namespace pr33140_3 {
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typedef struct Y { unsigned int c; } Y_t;
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struct X {
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Y_t a;
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};
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struct X foo[2] = {[0 ... 1] = {.a = (Y_t){.c = 0}}}; // expected-warning {{C99 extension}}
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}
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namespace pr33140_6 {
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struct Y { unsigned int c; };
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struct X { struct Y *p; };
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int f() {
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// FIXME: This causes clang to crash.
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//return (struct X[2]){ [0 ... 1] = { .p = &(struct Y&)(struct Y&&)(struct Y){0} } }[0].p->c;
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return 0;
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}
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}
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namespace pr33140_10 {
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int a(const int &n = 0);
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bool b() { return a() == a(); }
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}
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