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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
68 lines
1.7 KiB
C++
68 lines
1.7 KiB
C++
// RUN: %clang_cc1 -fsyntax-only -Wself-assign -verify %s
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void f() {
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int a = 42, b = 42;
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a = a; // expected-warning{{explicitly assigning}}
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b = b; // expected-warning{{explicitly assigning}}
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a = b;
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b = a = b;
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a = a = a; // expected-warning{{explicitly assigning}}
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a = b = b = 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; // expected-warning {{explicitly assigning}}
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a |= a; // expected-warning {{explicitly assigning}}
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a ^= a;
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}
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// Dummy type.
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struct S {};
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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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int a = 42;
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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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// Volatile stores aren't side-effect free.
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volatile int vol_a;
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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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// Do not diagnose self-assigment in an unevaluated context
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void false_positives_unevaluated_ctx(int a) 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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template <typename T>
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void g() {
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T a;
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a = a; // expected-warning{{explicitly assigning}}
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}
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void instantiate() {
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g<int>();
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g<S>();
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}
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