Open Quuxplusone opened 8 years ago
Quuxplusone
commented
8 years ago | Bugzilla Link | PR25683 |
| Status | NEW |
| Importance | P normal |
| Reported by | Tim Prince (trprince@synopsys.com) |
| Reported on | 2015-11-30 16:48:48 -0800 |
| Last modified on | 2019-07-02 10:26:38 -0700 |
| Version | 3.7 |
| Hardware | All All |
| CC | llvm-bugs@lists.llvm.org, sig-rnd-sat-clang-bugs@synopsys.com, thonerma@synopsys.com |
| Fixed by commit(s) | |
| Attachments | |
| Blocks | |
| Blocked by | |
| See also |
Quuxplusone
commented
5 years ago I updated the summary as this issue occurs for all instantiated out-of-line
defaulted special member function definitions, not just constructors. It does
not occur for non-defaulted definitions (the following test case includes a
member function for comparison purposes):
$ cat t.cpp
template<typename T>
struct S {
S();
S(const S&);
S(S&&);
~S();
S& operator=(const S&);
S& operator=(S&&);
void mf();
T dm;
};
template<typename T>
S<T>::S() = default;
template<typename T>
S<T>::S(const S<T>&) = default;
template<typename T>
S<T>::S(S<T>&&) = default;
template<typename T>
S<T>::~S() = default;
template<typename T>
S<T>& S<T>::operator=(const S<T>&) = default;
template<typename T>
S<T>& S<T>::operator=(S<T>&&) = default;
template<typename T>
void S<T>::mf() {}
void instantiate_all_the_things() {
S<int> s1;
S<int> s2(s1);
S<int> s3(static_cast<S<int>&&>(s2));
s2 = s1;
s3 = static_cast<S<int>&&>(s2);
s3.mf();
}
$ clang --version
clang version 8.0.0 (tags/RELEASE_800/final)
Target: x86_64-unknown-linux-gnu
...
$ clang -c -Xclang -ast-dump t.cpp
TranslationUnitDecl 0x5efc378 <<invalid sloc>> <invalid sloc>
...
|-ClassTemplateDecl 0x5f38368 <t.cpp:1:1, line:11:1> line:2:8 S
...
| `-ClassTemplateSpecializationDecl 0x5f69b00 <line:1:1, line:11:1> line:2:8
struct S definition
...
| |-CXXConstructorDecl 0x5f6a660 <line:13:1, line:3:5> col:3 used S 'void ()
noexcept' default
...
| |-CXXConstructorDecl 0x5f6a828 <line:15:1, line:4:13> col:3 used constexpr
S 'void (const S<int> &) noexcept' default
...
| |-CXXConstructorDecl 0x5f6a9f8 <line:17:1, line:5:8> col:3 used constexpr S
'void (S<int> &&) noexcept' default
...
| |-CXXDestructorDecl 0x5f6aad8 <line:19:1, line:6:6> col:3 used ~S 'void ()
noexcept' default
...
| |-CXXMethodDecl 0x5f6acb8 <line:21:1, line:7:24> col:6 used operator=
'S<int> &(const S<int> &) noexcept' default
...
| |-CXXMethodDecl 0x5f6ae38 <line:23:1, line:8:19> col:6 used operator=
'S<int> &(S<int> &&) noexcept' default
...
| |-CXXMethodDecl 0x5f6aee8 <line:25:1, col:18> line:9:8 used mf 'void ()'
...
For each of the special member function declarations within the instantiated
class template specialization, note that the begin location corresponds to the
out-of-line definition, but that the end location corresponds to the in-class
declaration. The instantiation of the 'mf' member function illustrates the
expected behavior.Debugging revelations from the following minimal test case:
template<typename>
struct S {
S();
};
template<typename T>
S<T>::S() = default;
S<int> s;
With a break point set on clang::CXXConstructorDecl::Create(), a number of
constructions of CXXConstructorDecl are observed. The first is for the in-
class declaration at line 3. The second is for the out-of-line definition on
lines 5-6. The third is for the instantiation of the constructor for the
C<int> specialization; the case this bug is concerned with.
That third instance is created here:
lib/Sema/SemaTemplateInstantiateDecl.cpp:
1903 Decl *
1904 TemplateDeclInstantiator::VisitCXXMethodDecl(CXXMethodDecl *D,
1905 TemplateParameterList
*TemplateParams,
1906 bool IsClassScopeSpecialization) {
....
1983 SourceLocation StartLoc = D->getInnerLocStart();
....
1986 if (CXXConstructorDecl *Constructor = dyn_cast<CXXConstructorDecl>(D)) {
1987 Method = CXXConstructorDecl::Create(SemaRef.Context, Record,
1988 StartLoc, NameInfo, T, TInfo,
1989 Constructor->isExplicit(),
1990 Constructor->isInlineSpecified(),
1991 false, Constructor->isConstexpr());
1992 Method->setRangeEnd(Constructor->getEndLoc());
....
2196 }
Debugging revealed that 'D' corresponds to the first constructed
CXXConstructorDecl object corresponding to the in-class declaration. Note that
the provided 'StartLoc' is obtained from 'getInnerLocStart()' called for the in-
class declaration. Since the in-class declaration does not have a template
parameter list, this corresponds to the start location of that declaration,
line 3:3. The end location is then set to the end location of that declaration
at line 3:5, making the locations consistent.
What ends up happening is that a call to 'setInnerLocStart()' is made here:
lib/Sema/SemaTemplateInstantiateDecl.cpp:
3890 void Sema::InstantiateFunctionDefinition(SourceLocation
PointOfInstantiation,
3891 FunctionDecl *Function,
3892 bool Recursive,
3893 bool DefinitionRequired,
3894 bool AtEndOfTU) {
....
4018 // Copy the inner loc start from the pattern.
4019 Function->setInnerLocStart(PatternDecl->getInnerLocStart());
....
4100 }
Lines 4018-4019 above were added via the change in the following link to
correct source locations for such instantiations.
- https://github.com/llvm/llvm-
project/commit/12dcbf3eaa6d2c8b9ee814ddb8bf23bef644bfaf
The call to setInnerLocStart() changes the perceived beginning of the function
(since, for this declaration, there is no template parameter list). Within the
debugger, calling 'Function->dump()' before and after the call to
'setInnerLocStart()' demonstrates the change:
(gdb) p Function->dump()
CXXConstructorDecl 0xae44e88 <m1.cpp:3:3, col:5> col:3 used S 'void ()'
...
(gdb) p Function->dump()
CXXConstructorDecl 0xae44e88 <m1.cpp:6:1, line:3:5> col:3 used S 'void ()'
The same inconsistent location issue occurs here for non-defaulted functions as
well. However, for functions with bodies, the end location gets corrected
later by a call to 'setBody()' from 'Sema::ActOnFinishFunctionBody()':
lib/AST/Decl.cpp:
2741 void FunctionDecl::setBody(Stmt *B) {
2742 Body = B;
2743 if (B)
2744 EndRangeLoc = B->getEndLoc();
2745 }
However, even in this case, the non-inner begin location is never updated with
the result being:
Decl::Loc = begin location of the in-class declaration.
DeclaratorDecl::InnerLocStart = inner location of the out-of-line definition.
FunctionDecl::EndRangeLoc = end location of the out-of-line definition.
I'm not sure what the ramifications are of the begin and inner-begin locations
being out of sync like this.
The following change appears to suffice to work around this issue:
$ git diff
diff --git a/lib/Sema/SemaTemplateInstantiateDecl.cpp
b/lib/Sema/SemaTemplateInstantiateDecl.cpp
index e76a34c..a07742d 100644
--- a/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -4015,8 +4015,10 @@ void Sema::InstantiateFunctionDefinition(SourceLocation
PointOfInstantiation,
// unimported module.
Function->setVisibleDespiteOwningModule();
- // Copy the inner loc start from the pattern.
+ // Copy source locations from the pattern.
+ Function->setLocation(PatternDecl->getBeginLoc());
Function->setInnerLocStart(PatternDecl->getInnerLocStart());
+ Function->setRangeEnd(PatternDecl->getEndLoc());
EnterExpressionEvaluationContext EvalContext(
*this, Sema::ExpressionEvaluationContext::PotentiallyEvaluated);
With the above change, I get 9 test failures in the Clang test suite. I
haven't yet looked at the details of those failures.
Failing Tests (9):
Clang :: Index/cursor-ref-names.cpp
Clang :: Index/preamble_macro_template.cpp
Clang :: Index/recursive-cxx-member-calls.cpp
Clang :: SemaCXX/member-init.cpp
Clang :: SemaTemplate/virtual-member-functions.cpp
Clang :: Templight/templight-deduced-func.cpp
Clang :: Templight/templight-default-func-arg.cpp
Clang :: Templight/templight-exception-spec-func.cpp
Clang :: Templight/templight-explicit-template-arg.cpp
Expected Passes : 42326
Expected Failures : 170
Unsupported Tests : 679
Unexpected Failures: 9A proposed fix has been posted for review:
- https://reviews.llvm.org/D64087