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0cb7e7ca0c
The idiom:
```
DeclContext::lookup_result R = DeclContext::lookup(Name);
for (auto *D : R) {...}
```
is not safe when in the loop body we trigger deserialization from an AST file.
The deserialization can insert new declarations in the StoredDeclsList whose
underlying type is a vector. When the vector decides to reallocate its storage
the pointer we hold becomes invalid.
This patch replaces a SmallVector with an singly-linked list. The current
approach stores a SmallVector<NamedDecl*, 4> which is around 8 pointers.
The linked list is 3, 5, or 7. We do better in terms of memory usage for small
cases (and worse in terms of locality -- the linked list entries won't be near
each other, but will be near their corresponding declarations, and we were going
to fetch those memory pages anyway). For larger cases: the vector uses a
doubling strategy for reallocation, so will generally be between half-full and
full. Let's say it's 75% full on average, so there's N * 4/3 + 4 pointers' worth
of space allocated currently and will be 2N pointers with the linked list. So we
break even when there are N=6 entries and slightly lose in terms of memory usage
after that. We suspect that's still a win on average.
Thanks to @rsmith!
Differential revision: https://reviews.llvm.org/D91524
132 lines
2.9 KiB
C++
132 lines
2.9 KiB
C++
// RUN: %clang_cc1 -std=c++2a -include %s %s -ast-print -verify | FileCheck %s
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//
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// RUN: %clang_cc1 -std=c++2a -emit-pch %s -o %t-cxx2a
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// RUN: %clang_cc1 -std=c++2a -include-pch %t-cxx2a %s -ast-print -verify | FileCheck %s
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// RUN: %clang_cc1 -std=c++2a -emit-pch -fpch-instantiate-templates %s -o %t-cxx2a
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// RUN: %clang_cc1 -std=c++2a -include-pch %t-cxx2a %s -ast-print -verify | FileCheck %s
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#ifndef USE_PCH
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namespace inheriting_constructor {
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struct S {};
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template<typename X, typename Y> struct T {
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template<typename A>
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explicit((Y{}, true)) T(A &&a) {}
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};
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template<typename X, typename Y> struct U : T<X, Y> {
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using T<X, Y>::T;
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};
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U<S, char> foo(char ch) {
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return U<S, char>(ch);
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}
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}
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#else
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namespace inheriting_constructor {
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U<S, char> a = foo('0');
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}
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//CHECK: explicit((char{} , true))
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#endif
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namespace basic {
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#ifndef USE_PCH
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struct B {};
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struct A {
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explicit A(int);
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explicit(false) operator bool();
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explicit(true) operator B();
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};
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#else
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//expected-note@-6+ {{candidate constructor}}
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//expected-note@-9+ {{candidate constructor}}
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//expected-note-re@-7+ {{explicit constructor is not a candidate{{$}}}}
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//expected-note@-7+ {{candidate function}}
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//expected-note@-7+ {{explicit conversion function is not a candidate (explicit specifier evaluates to true)}}
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//CHECK: explicit{{ +}}A(
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//CHECK-NEXT: explicit(false){{ +}}operator
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//CHECK-NEXT: explicit(true){{ +}}operator
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A a = 0; //expected-error {{no viable conversion}}
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A a1(0);
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bool b = a1;
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B b1 = a1; //expected-error {{no viable conversion}}
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#endif
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}
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namespace templ {
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#ifndef USE_PCH
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template<bool b>
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struct B {
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static constexpr bool value = b;
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};
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template<bool b>
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struct A {
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explicit(b) A(B<b>) {}
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template<typename T>
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explicit(b ^ T::value) operator T();
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};
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B<true> b_true;
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B<false> b_false;
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#else
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//expected-note@-8 {{candidate template ignored}}
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//expected-note@-8 {{explicit constructor declared here}}
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//expected-note@-15+ {{candidate constructor}}
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//expected-note@-8+ {{explicit conversion function is not a candidate (explicit specifier}}
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//expected-note@-11 {{explicit constructor is not a candidate (explicit specifier}}
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//CHECK: explicit(b){{ +}}A
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//CHECK: explicit(b{{ +}}^{{ +}}T::value){{ +}}operator
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A a = { b_true }; //expected-error {{class template argument deduction}}
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A a0 = b_true; //expected-error {{no viable constructor or deduction guide}}
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A a_true(b_true);
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A a_false = b_false;
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B<true> b = a_true;
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B<true> b1 = a_false; //expected-error {{no viable conversion}}
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B<false> b2(a_true);
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#endif
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}
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namespace guide {
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#ifndef USE_PCH
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template<typename T>
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struct A {
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A(T);
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};
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template<typename T>
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explicit(true) A(T) -> A<T>;
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explicit(false) A(int) -> A<int>;
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#else
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//expected-note@-5 {{explicit deduction guide}}
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//CHECK: explicit(true){{ +}}A(
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//CHECK: explicit(false){{ +}}A(
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A a = { 0.0 }; //expected-error {{explicit deduction guide}}
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A a1 = { 0 };
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#endif
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}
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#define USE_PCH
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