61061d69ea
Summary: This has just bit me, so i though it would be nice to avoid that next time :) Motivational case: https://godbolt.org/g/cq9UNk Basically, it's likely to happen if you don't like shadowing issues, and use `-Wshadow` and friends. And it won't be diagnosed by clang. The reason is, these self-assign diagnostics only work for builtin assignment operators. Which makes sense, one could have a very special operator=, that does something unusual in case of self-assignment, so it may make sense to not warn on that. But while it may be intentional in some cases, it may be a bug in other cases, so it would be really great to have some diagnostic about it... Reviewers: aaron.ballman, rsmith, rtrieu, nikola, rjmccall, dblaikie Reviewed By: rjmccall Subscribers: EricWF, lebedev.ri, thakis, Quuxplusone, cfe-commits Differential Revision: https://reviews.llvm.org/D44883 llvm-svn: 329493
118 lines
2.6 KiB
C++
118 lines
2.6 KiB
C++
// RUN: %clang_cc1 -fsyntax-only -Wself-assign-field -verify %s
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struct C {
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int a;
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int b;
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void f() {
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a = a; // expected-warning {{assigning field to itself}}
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b = b; // expected-warning {{assigning field to itself}}
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a = b;
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this->a = a; // expected-warning {{assigning field to itself}}
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this->b = b; // expected-warning {{assigning field to itself}}
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a = this->a; // expected-warning {{assigning field to itself}}
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b = this->b; // expected-warning {{assigning field to itself}}
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this->a = this->a; // expected-warning {{assigning field to itself}}
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this->b = this->b; // expected-warning {{assigning field to itself}}
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a = b;
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a = this->b;
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this->a = b;
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this->a = this->b;
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a *= a;
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a /= a;
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a %= a;
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a += a;
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a -= a;
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a <<= a;
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a >>= a;
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a &= a;
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a |= a;
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a ^= a;
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}
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void false_positives() {
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#define OP =
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#define LHS a
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#define RHS a
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// These shouldn't warn due to the use of the preprocessor.
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a OP a;
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LHS = a;
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a = RHS;
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LHS OP RHS;
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#undef OP
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#undef LHS
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#undef RHS
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// A way to silence the warning.
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a = (int &)a;
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}
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// Do not diagnose self-assigment in an unevaluated context
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void false_positives_unevaluated_ctx() noexcept(noexcept(a = a)) // expected-warning {{expression with side effects has no effect in an unevaluated context}}
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{
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decltype(a = a) b = a; // expected-warning {{expression with side effects has no effect in an unevaluated context}}
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static_assert(noexcept(a = a), ""); // expected-warning {{expression with side effects has no effect in an unevaluated context}}
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static_assert(sizeof(a = a), ""); // expected-warning {{expression with side effects has no effect in an unevaluated context}}
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}
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volatile int vol_a;
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void vol_test() {
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// Volatile stores aren't side-effect free.
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vol_a = vol_a;
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volatile int &vol_a_ref = vol_a;
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vol_a_ref = vol_a_ref;
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}
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};
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// Dummy type.
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struct Dummy {};
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template <typename T>
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struct TemplateClass {
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T var;
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void f() {
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var = var; // expected-warning {{assigning field to itself}}
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}
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};
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void instantiate() {
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{
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TemplateClass<int> c;
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c.f();
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}
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{
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TemplateClass<Dummy> c;
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c.f();
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}
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}
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// It may make sense not to warn on the rest of the tests.
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// It may be a valid use-case to self-assign to tell the compiler that
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// it is ok to vectorize the store.
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void f0(C *s, C *t) {
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s->a = s->a;
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t->a = s->a;
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}
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void f1(C &s, C &t) {
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s.a = s.a;
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t.a = s.a;
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}
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struct T {
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C *s;
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};
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void f2(T *t, T *t2) {
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t->s->a = t->s->a;
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t2->s->a = t->s->a;
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}
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void f3(T &t, T &t2) {
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t.s->a = t.s->a;
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t2.s->a = t.s->a;
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}
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