--- /dev/null
+========
+ABI tags
+========
+
+Introduction
+============
+
+This text tries to describe gcc semantic for mangling "abi_tag" attributes
+described in https://gcc.gnu.org/onlinedocs/gcc/C_002b_002b-Attributes.html
+
+There is no guarantee the following rules are correct, complete or make sense
+in any way as they were determined empirically by experiments with gcc5.
+
+Declaration
+===========
+
+ABI tags are declared in an abi_tag attribute and can be applied to a
+function, variable, class or inline namespace declaration. The attribute takes
+one or more strings (called tags); the order does not matter.
+
+See https://gcc.gnu.org/onlinedocs/gcc/C_002b_002b-Attributes.html for
+details.
+
+Tags on an inline namespace are called "implicit tags", all other tags are
+"explicit tags".
+
+Mangling
+========
+
+All tags that are "active" on an <unqualified-name> are emitted after the
+<unqualified-name>, before <template-args> or <discriminator>, and are part of
+the same <substitution> the <unqualified-name> is.
+
+They are mangled as:
+
+ <abi-tags> ::= <abi-tag>* # sort by name
+ <abi-tag> ::= B <tag source-name>
+
+Example:
+
+ __attribute__((abi_tag("test")))
+ void Func();
+
+ gets mangled as: _Z4FuncB4testv (prettified as `Func[abi:test]()`)
+
+Active tags
+===========
+
+A namespace does not have any active tags. For types (class / struct / union /
+enum), the explicit tags are the active tags.
+
+For variables and functions, the active tags are the explicit tags plus any
+"required tags" which are not in the "available tags" set:
+
+ derived-tags := (required-tags - available-tags)
+ active-tags := explicit-tags + derived-tags
+
+Required tags for a function
+============================
+
+If a function is used as a local scope for another name, and is part of
+another function as local scope, it doesn't have any required tags.
+
+If a function is used as a local scope for a guard variable name, it doesn't
+have any required tags.
+
+Otherwise the function requires any implicit or explicit tag used in the name
+for the return type.
+
+Example:
+ namespace A {
+ inline namespace B __attribute__((abi_tag)) {
+ struct C { int x; };
+ }
+ }
+
+ A::C foo();
+
+ gets mangled as: _Z3fooB1Bv (prettified as `foo[abi:B]()`)
+
+Required tags for a variable
+============================
+
+A variable requires any implicit or explicit tag used in its type.
+
+Available tags
+==============
+
+All tags used in the prefix and in the template arguments for a name are
+available. Also, for functions, all tags from the <bare-function-type>
+(which might include the return type for template functions) are available.
+
+For <local-name>s all active tags used in the local part (<function-
+encoding>) are available, but not implicit tags which were not active.
+
+Implicit and explicit tags used in the <unqualified-name> for a function (as
+in the type of a cast operator) are NOT available.
+
+Example: a cast operator to std::string (which is
+std::__cxx11::basic_string<...>) will use 'cxx11' as an active tag, as it is
+required from the return type `std::string` but not available.
// Attributes begin here
//
+def AbiTag : Attr {
+ let Spellings = [GCC<"abi_tag">];
+ let Args = [VariadicStringArgument<"Tags">];
+ let Subjects = SubjectList<[Struct, Var, Function, Namespace], ErrorDiag,
+ "ExpectedStructClassVariableFunctionOrInlineNamespace">;
+ let Documentation = [AbiTagsDocs];
+}
+
def AddressSpace : TypeAttr {
let Spellings = [GNU<"address_space">];
let Args = [IntArgument<"AddressSpace">];
optimizations like C++'s named return value optimization (NRVO).
}];
}
+
+def AbiTagsDocs : Documentation {
+ let Content = [{
+The ``abi_tag`` attribute can be applied to a function, variable, class or
+inline namespace declaration to modify the mangled name of the entity. It gives
+the ability to distinguish between different versions of the same entity but
+with different ABI versions supported. For example, a newer version of a class
+could have a different set of data members and thus have a different size. Using
+the ``abi_tag`` attribute, it is possible to have different mangled names for
+a global variable of the class type. Therefor, the old code could keep using
+the old manged name and the new code will use the new mangled name with tags.
+ }];
+}
"variables, functions and classes|Objective-C protocols|"
"functions and global variables|structs, unions, and typedefs|structs and typedefs|"
"interface or protocol declarations|kernel functions|non-K&R-style functions|"
- "variables, enums, fields and typedefs|functions, methods, enums, and classes}1">,
+ "variables, enums, fields and typedefs|functions, methods, enums, and classes|"
+ "structs, classes, variables, functions, and inline namespaces}1">,
InGroup<IgnoredAttributes>;
def err_attribute_wrong_decl_type : Error<warn_attribute_wrong_decl_type.Text>;
def warn_type_attribute_wrong_type : Warning<
def err_redefinition_extern_inline : Error<
"redefinition of a 'extern inline' function %0 is not supported in "
"%select{C99 mode|C++}1">;
+def warn_attr_abi_tag_namespace : Warning<
+ "'abi_tag' attribute on %select{non-inline|anonymous}0 namespace ignored">,
+ InGroup<IgnoredAttributes>;
+def err_abi_tag_on_redeclaration : Error<
+ "cannot add 'abi_tag' attribute in a redeclaration">;
+def err_new_abi_tag_on_redeclaration : Error<
+ "'abi_tag' %0 missing in original declaration">;
def note_deleted_dtor_no_operator_delete : Note<
"virtual destructor requires an unambiguous, accessible 'operator delete'">;
ExpectedKernelFunction,
ExpectedFunctionWithProtoType,
ExpectedVariableEnumFieldOrTypedef,
- ExpectedFunctionMethodEnumOrClass
+ ExpectedFunctionMethodEnumOrClass,
+ ExpectedStructClassVariableFunctionOrInlineNamespace
};
} // end namespace clang
}
}
+ // Re-declaration cannot add abi_tag's.
+ if (const auto *NewAbiTagAttr = New->getAttr<AbiTagAttr>()) {
+ if (const auto *OldAbiTagAttr = Old->getAttr<AbiTagAttr>()) {
+ for (const auto &NewTag : NewAbiTagAttr->tags()) {
+ if (std::find(OldAbiTagAttr->tags_begin(), OldAbiTagAttr->tags_end(),
+ NewTag) == OldAbiTagAttr->tags_end()) {
+ Diag(NewAbiTagAttr->getLocation(),
+ diag::err_new_abi_tag_on_redeclaration)
+ << NewTag;
+ Diag(OldAbiTagAttr->getLocation(), diag::note_previous_declaration);
+ }
+ }
+ } else {
+ Diag(NewAbiTagAttr->getLocation(), diag::err_abi_tag_on_redeclaration);
+ Diag(Old->getLocation(), diag::note_previous_declaration);
+ }
+ }
+
if (!Old->hasAttrs())
return;
Attr.getRange(), S.Context, Attr.getAttributeSpellingListIndex()));
}
+static void handleAbiTagAttr(Sema &S, Decl *D, const AttributeList &Attr) {
+ SmallVector<StringRef, 4> Tags;
+ for (unsigned I = 0, E = Attr.getNumArgs(); I != E; ++I) {
+ StringRef Tag;
+ if (!S.checkStringLiteralArgumentAttr(Attr, I, Tag))
+ return;
+ Tags.push_back(Tag);
+ }
+
+ if (const auto *NS = dyn_cast<NamespaceDecl>(D)) {
+ if (!NS->isInline()) {
+ S.Diag(Attr.getLoc(), diag::warn_attr_abi_tag_namespace) << 0;
+ return;
+ }
+ if (NS->isAnonymousNamespace()) {
+ S.Diag(Attr.getLoc(), diag::warn_attr_abi_tag_namespace) << 1;
+ return;
+ }
+ if (Attr.getNumArgs() == 0)
+ Tags.push_back(NS->getName());
+ } else if (!checkAttributeAtLeastNumArgs(S, Attr, 1))
+ return;
+
+ // Store tags sorted and without duplicates.
+ std::sort(Tags.begin(), Tags.end());
+ Tags.erase(std::unique(Tags.begin(), Tags.end()), Tags.end());
+
+ D->addAttr(::new (S.Context)
+ AbiTagAttr(Attr.getRange(), S.Context, Tags.data(), Tags.size(),
+ Attr.getAttributeSpellingListIndex()));
+
+ // FIXME: remove this warning as soon as mangled part is ready.
+ S.Diag(Attr.getRange().getBegin(), diag::warn_attribute_ignored)
+ << Attr.getName();
+}
+
static void handleARMInterruptAttr(Sema &S, Decl *D,
const AttributeList &Attr) {
// Check the attribute arguments.
case AttributeList::AT_Thread:
handleDeclspecThreadAttr(S, D, Attr);
break;
+ case AttributeList::AT_AbiTag:
+ handleAbiTagAttr(S, D, Attr);
+ break;
// Thread safety attributes:
case AttributeList::AT_AssertExclusiveLock:
--- /dev/null
+// RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify %s
+
+namespace N1 {
+
+namespace __attribute__((__abi_tag__)) {}
+// expected-warning@-1 {{'abi_tag' attribute on non-inline namespace ignored}}
+
+namespace N __attribute__((__abi_tag__)) {}
+// expected-warning@-1 {{'abi_tag' attribute on non-inline namespace ignored}}
+
+} // namespace N1
+
+namespace N2 {
+
+inline namespace __attribute__((__abi_tag__)) {}
+// expected-warning@-1 {{'abi_tag' attribute on anonymous namespace ignored}}
+
+inline namespace N __attribute__((__abi_tag__)) {}
+// FIXME: remove this warning as soon as attribute fully supported.
+// expected-warning@-2 {{'__abi_tag__' attribute ignored}}
+
+} // namespcace N2
+
+__attribute__((abi_tag("B", "A"))) extern int a1;
+// FIXME: remove this warning as soon as attribute fully supported.
+// expected-warning@-2 {{'abi_tag' attribute ignored}}
+
+__attribute__((abi_tag("A", "B"))) extern int a1;
+// expected-note@-1 {{previous declaration is here}}
+// FIXME: remove this warning as soon as attribute fully supported.
+// expected-warning@-3 {{'abi_tag' attribute ignored}}
+
+__attribute__((abi_tag("A", "C"))) extern int a1;
+// expected-error@-1 {{'abi_tag' C missing in original declaration}}
+// FIXME: remove this warning as soon as attribute fully supported.
+// expected-warning@-3 {{'abi_tag' attribute ignored}}
+
+extern int a2;
+// expected-note@-1 {{previous declaration is here}}
+__attribute__((abi_tag("A")))extern int a2;
+// expected-error@-1 {{cannot add 'abi_tag' attribute in a redeclaration}}
+// FIXME: remove this warning as soon as attribute fully supported.
+// expected-warning@-3 {{'abi_tag' attribute ignored}}
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