b59ab701e9
In C++, the type of an enumerator is the type of the enumeration,
whereas in C, the type of the enumerator is 'int'. The type of a comma
operator is the type of the right-hand operand, which means you can get
an implicit conversion with this code in C but not in C++:
```
enum E { Zero };
enum E foo() {
return ((void)0, Zero);
}
```
We were previously incorrectly diagnosing this code as being
incompatible with C++ because the type of the paren expression would be
'int' there, whereas in C++ the type is 'E'.
So now we handle the comma operator with special logic when analyzing
implicit conversions in C. When analyzing the left-hand operand of a
comma operator, we do not need to check for that operand causing an
implicit conversion for the entire comma expression. So we only check
for that case with the right-hand operand.
This addresses a concern brought up post-commit:
https://github.com/llvm/llvm-project/pull/137658#issuecomment-2854525259
75 lines
3.1 KiB
C
75 lines
3.1 KiB
C
// RUN: %clang_cc1 -fsyntax-only -verify -Wimplicit-int-enum-cast %s
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// RUN: %clang_cc1 -fsyntax-only -verify -Wc++-compat %s
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// RUN: %clang_cc1 -fsyntax-only -verify=cxx -x c++ %s
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// RUN: %clang_cc1 -fsyntax-only -verify=good -Wno-implicit-enum-enum-cast %s
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// RUN: %clang_cc1 -fsyntax-only -verify=good -Wc++-compat -Wno-implicit-enum-enum-cast -Wno-implicit-int-enum-cast %s
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// good-no-diagnostics
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enum E1 {
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E1_Zero,
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E1_One
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};
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enum E2 {
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E2_Zero
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};
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struct S {
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enum E1 e;
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} s = { 12 }; // expected-warning {{implicit conversion from 'int' to enumeration type 'enum E1' is invalid in C++}} \
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cxx-error {{cannot initialize a member subobject of type 'enum E1' with an rvalue of type 'int'}}
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enum E1 foo(void) {
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int x;
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enum E1 e = 12; // expected-warning {{implicit conversion from 'int' to enumeration type 'enum E1' is invalid in C++}} \
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cxx-error {{cannot initialize a variable of type 'enum E1' with an rvalue of type 'int'}}
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// Enum to integer is fine.
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x = e;
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// Integer to enum is not fine.
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e = x; // expected-warning {{implicit conversion from 'int' to enumeration type 'enum E1' is invalid in C++}} \
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cxx-error {{assigning to 'enum E1' from incompatible type 'int'}}
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return x; // expected-warning {{implicit conversion from 'int' to enumeration type 'enum E1' is invalid in C++}} \
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cxx-error {{cannot initialize return object of type 'enum E1' with an lvalue of type 'int'}}
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}
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// Returning with the correct types is fine.
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enum E1 bar(void) {
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return E1_Zero;
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}
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// Enum to different-enum conversion is also a C++ incompatibility, but is
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// handled via a more general diagnostic, -Wimplicit-enum-enum-cast, which is
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// on by default.
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enum E1 quux(void) {
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enum E1 e1 = E2_Zero; // expected-warning {{implicit conversion from enumeration type 'enum E2' to different enumeration type 'enum E1'}} \
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cxx-error {{cannot initialize a variable of type 'enum E1' with an rvalue of type 'E2'}}
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e1 = E2_Zero; // expected-warning {{implicit conversion from enumeration type 'enum E2' to different enumeration type 'enum E1'}} \
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cxx-error {{assigning to 'enum E1' from incompatible type 'E2'}}
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return E2_Zero; // expected-warning {{implicit conversion from enumeration type 'enum E2' to different enumeration type 'enum E1'}} \
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cxx-error {{cannot initialize return object of type 'enum E1' with an rvalue of type 'E2'}}
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}
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enum E1 comma1(void) {
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return ((void)0, E1_One);
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}
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enum E1 comma2(void) {
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enum E1 x;
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return
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(x = 12, // expected-warning {{implicit conversion from 'int' to enumeration type 'enum E1' is invalid in C++}} \
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cxx-error {{assigning to 'enum E1' from incompatible type 'int'}}
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E1_One);
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}
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enum E1 comma3(void) {
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enum E1 x;
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return ((void)0, foo()); // Okay, no conversion in C++
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}
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enum E1 comma4(void) {
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return ((void)1, 2); // expected-warning {{implicit conversion from 'int' to enumeration type 'enum E1' is invalid in C++}} \
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cxx-error {{cannot initialize return object of type 'enum E1' with an rvalue of type 'int'}}
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}
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