constexpr Expansion Statement in constexpr Function

[l3bot]

In GitLab by @DarkArc on Jan 10, 2019, 10:18

We're reviving https://gitlab.com/lock3/clang/issues/102, to an extent. We'll inspect the type of the range var, if decay would occur, we'll use auto&&, if decay would not occur, we'll use auto.

[l3bot]

In GitLab by @DarkArc on Jan 10, 2019, 10:57

There seems to be another underlying issue with expansion statements that prevents this from being an easy fix.

Source:

#include <experimental/meta>

using namespace std::experimental;

namespace std {

template<typename I>
constexpr int distance(I first, I last) {
  int n = 0;
  while (first != last) {
    ++first;
    ++n;
  }
  return n;
}

template<typename I>
constexpr I next(I iter, int advancement) {
  for (int i = 0; i < advancement; ++i)
    ++iter;
  return iter;
}

template<class ...TupleValType>
class tuple {
};

} // namespace std

namespace std::experimental::meta {
  inline namespace v1 {
    // Dummy to satisfy lookup requirements of
    // expansion statements.
    template<int Index, class ...TupleValType>
    int get(std::tuple<TupleValType...>& t) {
      return 0;
    }
  }
}

template<typename container_type, int target_index>
static constexpr meta::info get_fib() {
  constexpr const char* target_name = __concatenate("fib_", target_index);
  constexpr auto range = meta::range(reflexpr(container_type));

  for constexpr (meta::info member : range) {
    if (meta::name_of(member) == target_name)
      return member;
  }

  return meta::info();
}

class foo {
  constexpr static int fib_0 = 0;
  constexpr static int fib_1 = 1;
  constexpr static int fib_2 = 1;
};

int main() {
  constexpr meta::info result = get_fib<foo, 1>();
  return 0;
}

Error:

0.      Program arguments: /build_env/new-impl/llvm-build/bin/clang-8 -cc1 -triple x86_64-unknown-linux-gnu -emit-obj -mrelax-all -disable-free -main-file-name scratch.cpp -mrelocation-model static -mthread-model posix -mdisable-fp-elim -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -fuse-init-array -target-cpu x86-64 -dwarf-column-info -debugger-tuning=gdb -resource-dir /build_env/new-impl/llvm-build/lib/clang/8.0.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/8/../../../../include/c++/8 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/8/../../../../include/x86_64-linux-gnu/c++/8 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/8/../../../../include/x86_64-linux-gnu/c++/8 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/8/../../../../include/c++/8/backward -internal-isystem /usr/local/include -internal-isystem /build_env/new-impl/llvm-build/lib/clang/8.0.0/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -std=c++1z -fdeprecated-macro -fdebug-compilation-dir /build_env/new-impl/llvm-build -ferror-limit 19 -fmessage-length 362 -fobjc-runtime=gcc -fcxx-exceptions -fexceptions -freflection -fdiagnostics-show-option -fcolor-diagnostics -o /tmp/scratch-09b5b1.o -x c++ ../clang/test/CXX/meta/scratch.cpp -faddrsig 
1.      ../clang/test/CXX/meta/scratch.cpp:61:50: current parser token ';'
2.      ../clang/test/CXX/meta/scratch.cpp:60:12: parsing function body 'main'
3.      ../clang/test/CXX/meta/scratch.cpp:60:12: in compound statement ('{}')
#0 0x000055cd053c8a7f llvm::sys::PrintStackTrace(llvm::raw_ostream&) /build_env/new-impl/llvm/lib/Support/Unix/Signals.inc:495:22
#1 0x000055cd053c8b12 PrintStackTraceSignalHandler(void*) /build_env/new-impl/llvm/lib/Support/Unix/Signals.inc:559:1
#2 0x000055cd053c6832 llvm::sys::RunSignalHandlers() /build_env/new-impl/llvm/lib/Support/Signals.cpp:67:20
#3 0x000055cd053c84a4 SignalHandler(int) /build_env/new-impl/llvm/lib/Support/Unix/Signals.inc:358:1
#4 0x00007efe7d546890 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x12890)
#5 0x00007efe7c1f7e97 gsignal /build/glibc-OTsEL5/glibc-2.27/signal/../sysdeps/unix/sysv/linux/raise.c:51:0
#6 0x00007efe7c1f9801 abort /build/glibc-OTsEL5/glibc-2.27/stdlib/abort.c:81:0
#7 0x00007efe7c1e939a __assert_fail_base /build/glibc-OTsEL5/glibc-2.27/assert/assert.c:89:0
#8 0x00007efe7c1e9412 (/lib/x86_64-linux-gnu/libc.so.6+0x30412)
#9 0x000055cd08d805e9 evaluateVarDeclInit((anonymous namespace)::EvalInfo&, clang::Expr const*, clang::VarDecl const*, (anonymous namespace)::CallStackFrame*, clang::APValue*&, (anonymous namespace)::LValue const*) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:2541:7
#10 0x000055cd08d82b82 findCompleteObject((anonymous namespace)::EvalInfo&, clang::Expr const*, AccessKinds, (anonymous namespace)::LValue const&, clang::QualType) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:3235:9
#11 0x000055cd08d832f7 handleLValueToRValueConversion((anonymous namespace)::EvalInfo&, clang::Expr const*, clang::QualType, (anonymous namespace)::LValue const&, clang::APValue&) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:3363:72
#12 0x000055cd08d88334 HandleConstructorCall(clang::Expr const*, (anonymous namespace)::LValue const&, clang::APValue*, clang::CXXConstructorDecl const*, (anonymous namespace)::EvalInfo&, clang::APValue&) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:4529:42
#13 0x000055cd08d88e82 HandleConstructorCall(clang::Expr const*, (anonymous namespace)::LValue const&, llvm::ArrayRef<clang::Expr const*>, clang::CXXConstructorDecl const*, (anonymous namespace)::EvalInfo&, clang::APValue&) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:4645:31
#14 0x000055cd08d9093e (anonymous namespace)::RecordExprEvaluator::VisitCXXConstructExpr(clang::CXXConstructExpr const*, clang::QualType) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:6937:31
#15 0x000055cd08d8f282 (anonymous namespace)::RecordExprEvaluator::VisitCXXConstructExpr(clang::CXXConstructExpr const*) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:6678:5
#16 0x000055cd08db2562 clang::StmtVisitorBase<clang::make_const_ptr, (anonymous namespace)::RecordExprEvaluator, bool>::Visit(clang::Stmt const*) /build_env/new-impl/llvm-build/tools/clang/include/clang/AST/StmtNodes.inc:237:1
#17 0x000055cd08d914fd EvaluateRecord(clang::Expr const*, (anonymous namespace)::LValue const&, clang::APValue&, (anonymous namespace)::EvalInfo&) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:7061:57
#18 0x000055cd08da313a Evaluate(clang::APValue&, (anonymous namespace)::EvalInfo&, clang::Expr const*) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:11070:9
#19 0x000055cd08d87618 EvaluateArgs(llvm::ArrayRef<clang::Expr const*>, llvm::SmallVector<clang::APValue, 8u>&, (anonymous namespace)::EvalInfo&) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:4409:9
#20 0x000055cd08d87730 HandleFunctionCall(clang::SourceLocation, clang::FunctionDecl const*, (anonymous namespace)::LValue const*, llvm::ArrayRef<clang::Expr const*>, clang::Stmt const*, (anonymous namespace)::EvalInfo&, clang::APValue&, (anonymous namespace)::LValue const*) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:4427:7
#21 0x000055cd08db19f7 (anonymous namespace)::ExprEvaluatorBase<(anonymous namespace)::RecordExprEvaluator>::handleCallExpr(clang::CallExpr const*, clang::APValue&, (anonymous namespace)::LValue const*) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:5000:28
#22 0x000055cd08d8f24e (anonymous namespace)::RecordExprEvaluator::VisitCallExpr(clang::CallExpr const*) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:6673:5
#23 0x000055cd08db27ea clang::StmtVisitorBase<clang::make_const_ptr, (anonymous namespace)::RecordExprEvaluator, bool>::Visit(clang::Stmt const*) /build_env/new-impl/llvm-build/tools/clang/include/clang/AST/StmtNodes.inc:401:1
#24 0x000055cd08d914fd EvaluateRecord(clang::Expr const*, (anonymous namespace)::LValue const&, clang::APValue&, (anonymous namespace)::EvalInfo&) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:7061:57
#25 0x000055cd08da35b8 EvaluateInPlace(clang::APValue&, (anonymous namespace)::EvalInfo&, (anonymous namespace)::LValue const&, clang::Expr const*, bool) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:11118:50
#26 0x000055cd08d8a369 (anonymous namespace)::LValueExprEvaluator::VisitMaterializeTemporaryExpr(clang::MaterializeTemporaryExpr const*) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:5668:7
#27 0x000055cd08dac584 clang::StmtVisitorBase<clang::make_const_ptr, (anonymous namespace)::LValueExprEvaluator, bool>::Visit(clang::Stmt const*) /build_env/new-impl/llvm-build/tools/clang/include/clang/AST/StmtNodes.inc:683:1
#28 0x000055cd08dca0ad (anonymous namespace)::ExprEvaluatorBase<(anonymous namespace)::LValueExprEvaluator>::VisitCastExpr(clang::CastExpr const*) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:5069:34
#29 0x000055cd08dab612 (anonymous namespace)::LValueExprEvaluatorBase<(anonymous namespace)::LValueExprEvaluator>::VisitCastExpr(clang::CastExpr const*) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:5448:50
#30 0x000055cd08d898fe (anonymous namespace)::LValueExprEvaluator::VisitCastExpr(clang::CastExpr const*) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:5530:56
#31 0x000055cd08dcbe5b clang::StmtVisitorBase<clang::make_const_ptr, (anonymous namespace)::LValueExprEvaluator, bool>::VisitImplicitCastExpr(clang::ImplicitCastExpr const*) /build_env/new-impl/llvm-build/tools/clang/include/clang/AST/StmtNodes.inc:495:1
#32 0x000055cd08dac2e4 clang::StmtVisitorBase<clang::make_const_ptr, (anonymous namespace)::LValueExprEvaluator, bool>::Visit(clang::Stmt const*) /build_env/new-impl/llvm-build/tools/clang/include/clang/AST/StmtNodes.inc:495:1
#33 0x000055cd08d89ac3 EvaluateLValue(clang::Expr const*, (anonymous namespace)::LValue&, (anonymous namespace)::EvalInfo&, bool) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:5557:66
#34 0x000055cd08d847f9 EvaluateObjectArgument((anonymous namespace)::EvalInfo&, clang::Expr const*, (anonymous namespace)::LValue&) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:3653:45
#35 0x000055cd08e07451 (anonymous namespace)::ExprEvaluatorBase<(anonymous namespace)::ReflectionEvaluator>::handleCallExpr(clang::CallExpr const*, clang::APValue&, (anonymous namespace)::LValue const*) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:4944:13
#36 0x000055cd08dfb8fb (anonymous namespace)::ExprEvaluatorBase<(anonymous namespace)::ReflectionEvaluator>::VisitCallExpr(clang::CallExpr const*) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:4880:9
#37 0x000055cd08dfb9bb clang::StmtVisitorBase<clang::make_const_ptr, (anonymous namespace)::ReflectionEvaluator, bool>::VisitCXXOperatorCallExpr(clang::CXXOperatorCallExpr const*) /build_env/new-impl/llvm-build/tools/clang/include/clang/AST/StmtNodes.inc:417:1
#38 0x000055cd08dc8d3e clang::StmtVisitorBase<clang::make_const_ptr, (anonymous namespace)::ReflectionEvaluator, bool>::Visit(clang::Stmt const*) /build_env/new-impl/llvm-build/tools/clang/include/clang/AST/StmtNodes.inc:417:1
#39 0x000055cd08dfbe70 (anonymous namespace)::ExprEvaluatorBase<(anonymous namespace)::ReflectionEvaluator>::VisitExprWithCleanups(clang::ExprWithCleanups const*) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:4796:53
#40 0x000055cd08dc8fae clang::StmtVisitorBase<clang::make_const_ptr, (anonymous namespace)::ReflectionEvaluator, bool>::Visit(clang::Stmt const*) /build_env/new-impl/llvm-build/tools/clang/include/clang/AST/StmtNodes.inc:613:1
#41 0x000055cd08da2a71 EvaluateReflection(clang::Expr const*, clang::APValue&, (anonymous namespace)::EvalInfo&) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:11013:51
#42 0x000055cd08da2c88 Evaluate(clang::APValue&, (anonymous namespace)::EvalInfo&, clang::Expr const*) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:11036:9
#43 0x000055cd08da3657 EvaluateInPlace(clang::APValue&, (anonymous namespace)::EvalInfo&, (anonymous namespace)::LValue const&, clang::Expr const*, bool) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:11127:34
#44 0x000055cd08d8550f EvaluateVarDecl((anonymous namespace)::EvalInfo&, clang::VarDecl const*) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:3847:7
#45 0x000055cd08d855d5 EvaluateDecl((anonymous namespace)::EvalInfo&, clang::Decl const*) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:3861:8
#46 0x000055cd08d861eb EvaluateStmt((anonymous namespace)::StmtResult&, (anonymous namespace)::EvalInfo&, clang::Stmt const*, clang::SwitchCase const*) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:4089:11
#47 0x000055cd08d863f6 EvaluateStmt((anonymous namespace)::StmtResult&, (anonymous namespace)::EvalInfo&, clang::Stmt const*, clang::SwitchCase const*) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:4111:40
#48 0x000055cd08d86dc9 EvaluateStmt((anonymous namespace)::StmtResult&, (anonymous namespace)::EvalInfo&, clang::Stmt const*, clang::SwitchCase const*) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:4271:25
#49 0x000055cd08d863f6 EvaluateStmt((anonymous namespace)::StmtResult&, (anonymous namespace)::EvalInfo&, clang::Stmt const*, clang::SwitchCase const*) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:4111:40
#50 0x000055cd08d87b07 HandleFunctionCall(clang::SourceLocation, clang::FunctionDecl const*, (anonymous namespace)::LValue const*, llvm::ArrayRef<clang::Expr const*>, clang::Stmt const*, (anonymous namespace)::EvalInfo&, clang::APValue&, (anonymous namespace)::LValue const*) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:4471:36
#51 0x000055cd08e07825 (anonymous namespace)::ExprEvaluatorBase<(anonymous namespace)::ReflectionEvaluator>::handleCallExpr(clang::CallExpr const*, clang::APValue&, (anonymous namespace)::LValue const*) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:5000:28
#52 0x000055cd08dfb8fb (anonymous namespace)::ExprEvaluatorBase<(anonymous namespace)::ReflectionEvaluator>::VisitCallExpr(clang::CallExpr const*) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:4880:9
#53 0x000055cd08dc8cf6 clang::StmtVisitorBase<clang::make_const_ptr, (anonymous namespace)::ReflectionEvaluator, bool>::Visit(clang::Stmt const*) /build_env/new-impl/llvm-build/tools/clang/include/clang/AST/StmtNodes.inc:401:1
#54 0x000055cd08da2a71 EvaluateReflection(clang::Expr const*, clang::APValue&, (anonymous namespace)::EvalInfo&) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:11013:51
#55 0x000055cd08da2c88 Evaluate(clang::APValue&, (anonymous namespace)::EvalInfo&, clang::Expr const*) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:11036:9
#56 0x000055cd08da3657 EvaluateInPlace(clang::APValue&, (anonymous namespace)::EvalInfo&, (anonymous namespace)::LValue const&, clang::Expr const*, bool) /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:11127:34
#57 0x000055cd08da4461 clang::Expr::EvaluateAsInitializer(clang::APValue&, clang::ASTContext const&, clang::VarDecl const*, llvm::SmallVectorImpl<std::pair<clang::SourceLocation, clang::PartialDiagnostic> >&) const /build_env/new-impl/llvm/tools/clang/lib/AST/ExprConstant.cpp:11303:7
#58 0x000055cd08cfb1f4 clang::VarDecl::evaluateValue(llvm::SmallVectorImpl<std::pair<clang::SourceLocation, clang::PartialDiagnostic> >&) const /build_env/new-impl/llvm/tools/clang/lib/AST/Decl.cpp:2286:44
#59 0x000055cd07f09ebd clang::Sema::CheckCompleteVariableDeclaration(clang::VarDecl*) /build_env/new-impl/llvm/tools/clang/lib/Sema/SemaDecl.cpp:12033:38
#60 0x000055cd07f07fcf clang::Sema::AddInitializerToDecl(clang::Decl*, clang::Expr*, bool) /build_env/new-impl/llvm/tools/clang/lib/Sema/SemaDecl.cpp:11540:35
#61 0x000055cd07a3ef07 clang::Parser::ParseDeclarationAfterDeclaratorAndAttributes(clang::Declarator&, clang::Parser::ParsedTemplateInfo const&, clang::Parser::ForRangeInit*) /build_env/new-impl/llvm/tools/clang/lib/Parse/ParseDecl.cpp:2304:37
#62 0x000055cd07a3dbee clang::Parser::ParseDeclGroup(clang::ParsingDeclSpec&, clang::DeclaratorContext, clang::SourceLocation*, clang::Parser::ForRangeInit*) /build_env/new-impl/llvm/tools/clang/lib/Parse/ParseDecl.cpp:2042:35
#63 0x000055cd07a3cdf5 clang::Parser::ParseSimpleDeclaration(clang::DeclaratorContext, clang::SourceLocation&, clang::Parser::ParsedAttributesWithRange&, bool, clang::Parser::ForRangeInit*) /build_env/new-impl/llvm/tools/clang/lib/Parse/ParseDecl.cpp:1766:51
#64 0x000055cd07a3ca98 clang::Parser::ParseDeclaration(clang::DeclaratorContext, clang::SourceLocation&, clang::Parser::ParsedAttributesWithRange&) /build_env/new-impl/llvm/tools/clang/lib/Parse/ParseDecl.cpp:1707:64
#65 0x000055cd07ae605d clang::Parser::ParseStatementOrDeclarationAfterAttributes(llvm::SmallVector<clang::Stmt*, 32u>&, clang::Parser::AllowedConstructsKind, clang::SourceLocation*, clang::Parser::ParsedAttributesWithRange&) /build_env/new-impl/llvm/tools/clang/lib/Parse/ParseStmt.cpp:215:60
#66 0x000055cd07ae5aa5 clang::Parser::ParseStatementOrDeclaration(llvm::SmallVector<clang::Stmt*, 32u>&, clang::Parser::AllowedConstructsKind, clang::SourceLocation*) /build_env/new-impl/llvm/tools/clang/lib/Parse/ParseStmt.cpp:111:45
#67 0x000055cd07ae8d8a clang::Parser::ParseCompoundStatementBody(bool) /build_env/new-impl/llvm/tools/clang/lib/Parse/ParseStmt.cpp:997:53
#68 0x000055cd07aecbcb clang::Parser::ParseFunctionStatementBody(clang::Decl*, clang::Parser::ParseScope&) /build_env/new-impl/llvm/tools/clang/lib/Parse/ParseStmt.cpp:2014:48
#69 0x000055cd07a19593 clang::Parser::ParseFunctionDefinition(clang::ParsingDeclarator&, clang::Parser::ParsedTemplateInfo const&, clang::Parser::LateParsedAttrList*) /build_env/new-impl/llvm/tools/clang/lib/Parse/Parser.cpp:1246:36
#70 0x000055cd07a3d834 clang::Parser::ParseDeclGroup(clang::ParsingDeclSpec&, clang::DeclaratorContext, clang::SourceLocation*, clang::Parser::ForRangeInit*) /build_env/new-impl/llvm/tools/clang/lib/Parse/ParseDecl.cpp:1983:34
#71 0x000055cd07a18523 clang::Parser::ParseDeclOrFunctionDefInternal(clang::Parser::ParsedAttributesWithRange&, clang::ParsingDeclSpec&, clang::AccessSpecifier) /build_env/new-impl/llvm/tools/clang/lib/Parse/Parser.cpp:1016:1
#72 0x000055cd07a185fd clang::Parser::ParseDeclarationOrFunctionDefinition(clang::Parser::ParsedAttributesWithRange&, clang::ParsingDeclSpec*, clang::AccessSpecifier) /build_env/new-impl/llvm/tools/clang/lib/Parse/Parser.cpp:1031:57
#73 0x000055cd07a17bbe clang::Parser::ParseExternalDeclaration(clang::Parser::ParsedAttributesWithRange&, clang::ParsingDeclSpec*) (.localalias.1) /build_env/new-impl/llvm/tools/clang/lib/Parse/Parser.cpp:856:58
#74 0x000055cd07a16e33 clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&) /build_env/new-impl/llvm/tools/clang/lib/Parse/Parser.cpp:610:42
#75 0x000055cd07a12aaa clang::ParseAST(clang::Sema&, bool, bool) /build_env/new-impl/llvm/tools/clang/lib/Parse/ParseAST.cpp:157:37
#76 0x000055cd05e79481 clang::ASTFrontendAction::ExecuteAction() /build_env/new-impl/llvm/tools/clang/lib/Frontend/FrontendAction.cpp:1018:11
#77 0x000055cd063d1dba clang::CodeGenAction::ExecuteAction() /build_env/new-impl/llvm/tools/clang/lib/CodeGen/CodeGenAction.cpp:1045:1
#78 0x000055cd05e78e72 clang::FrontendAction::Execute() /build_env/new-impl/llvm/tools/clang/lib/Frontend/FrontendAction.cpp:921:38
#79 0x000055cd05e06800 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) /build_env/new-impl/llvm/tools/clang/lib/Frontend/CompilerInstance.cpp:969:24
#80 0x000055cd05fe0d57 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) /build_env/new-impl/llvm/tools/clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp:267:38
#81 0x000055cd03e81b12 cc1_main(llvm::ArrayRef<char const*>, char const*, void*) /build_env/new-impl/llvm/tools/clang/tools/driver/cc1_main.cpp:219:38
#82 0x000055cd03e76fdf ExecuteCC1Tool(llvm::ArrayRef<char const*>, llvm::StringRef) /build_env/new-impl/llvm/tools/clang/tools/driver/driver.cpp:310:64
#83 0x000055cd03e77c82 main /build_env/new-impl/llvm/tools/clang/tools/driver/driver.cpp:382:26
#84 0x00007efe7c1dab97 __libc_start_main /build/glibc-OTsEL5/glibc-2.27/csu/../csu/libc-start.c:344:0
#85 0x000055cd03e74a1a _start (/build_env/new-impl/llvm-build/bin/clang-8+0x1c0da1a)

[l3bot]

In GitLab by @sdgoodrick on Feb 28, 2019, 12:34

CHANGE LINE 45: for constexpr (meta::info member : range) TO: for... (constexpr meta::info member : range)

The program does not crash, but emits 12 errors on the feature/sdg/expansion branch. Please update the code.

wyattproblem.cpp:35:18: error: reference to 'tuple' is ambiguous
    int get(std::tuple<TupleValType...>& t) {
                 ^
/Users/sam/work/tests/../new-build/bin/../include/c++/v1/__tuple:162:52: note: 
      candidate found by name lookup is 'std::__1::tuple'
template <class ..._Tp> class _LIBCPP_TEMPLATE_VIS tuple;
                                                   ^
wyattproblem.cpp:25:7: note: candidate found by name lookup is 'std::tuple'
class tuple {
      ^
wyattproblem.cpp:35:13: error: use of class template 'tuple' requires template
      arguments; argument deduction not allowed in function prototype
    int get(std::tuple<TupleValType...>& t) {
            ^~~
wyattproblem.cpp:25:7: note: template is declared here
class tuple {
      ^
wyattproblem.cpp:35:23: error: expected ')'
    int get(std::tuple<TupleValType...>& t) {
                      ^
wyattproblem.cpp:35:12: note: to match this '('
    int get(std::tuple<TupleValType...>& t) {
           ^
wyattproblem.cpp:46:41: error: constexpr variable '__range' must be initialized
      by a constant expression
  for... (constexpr meta::info member : range) {
                                        ^~~~~
wyattproblem.cpp:61:33: note: in instantiation of function template
      specialization 'get_fib<foo, 1>' requested here
  constexpr meta::info result = get_fib<foo, 1>();
                                ^
wyattproblem.cpp:46:41: note: reference to 'range' is not a constant expression
  for... (constexpr meta::info member : range) {
                                        ^
wyattproblem.cpp:44:18: note: declared here
  constexpr auto range = meta::range(reflexpr(container_type));
                 ^
wyattproblem.cpp:46:39: error: constexpr variable '__begin' must be initialized
      by a constant expression
  for... (constexpr meta::info member : range) {
                                      ^
wyattproblem.cpp:46:39: note: initializer of '__range' is not a constant
      expression
wyattproblem.cpp:46:41: note: declared here
  for... (constexpr meta::info member : range) {
                                        ^
wyattproblem.cpp:46:39: error: constexpr variable '__end' must be initialized by
      a constant expression
  for... (constexpr meta::info member : range) {
                                      ^
wyattproblem.cpp:46:39: note: initializer of '__range' is not a constant
      expression
wyattproblem.cpp:46:41: note: declared here
  for... (constexpr meta::info member : range) {
                                        ^
In file included from wyattproblem.cpp:1:
/Users/sam/work/new-build/lib/clang/9.0.0/include/experimental/meta:955:7: error: 
      cannot decompose private member 'm_first' of
      'std::experimental::meta::v1::range'
class range {
      ^
/Users/sam/work/new-build/lib/clang/9.0.0/include/experimental/meta:956:12: note: 
      implicitly declared private here
  iterator m_first;
           ^
/Users/sam/work/new-build/lib/clang/9.0.0/include/experimental/meta:955:7: error: 
      cannot decompose private member 'm_last' of
      'std::experimental::meta::v1::range'
class range {
      ^
/Users/sam/work/new-build/lib/clang/9.0.0/include/experimental/meta:957:12: note: 
      implicitly declared private here
  iterator m_last;
           ^
/Users/sam/work/new-build/lib/clang/9.0.0/include/experimental/meta:955:7: error: 
      cannot decompose private member 'm_first' of
      'std::experimental::meta::v1::range'
class range {
      ^
wyattproblem.cpp:46:48: note: in instantiation of loop body expansion
  for... (constexpr meta::info member : range) {
                                               ^
wyattproblem.cpp:61:33: note: in instantiation of function template
      specialization 'get_fib<foo, 1>' requested here
  constexpr meta::info result = get_fib<foo, 1>();
                                ^
/Users/sam/work/new-build/lib/clang/9.0.0/include/experimental/meta:956:12: note: 
      implicitly declared private here
  iterator m_first;
           ^
/Users/sam/work/new-build/lib/clang/9.0.0/include/experimental/meta:955:7: error: 
      cannot decompose private member 'm_last' of
      'std::experimental::meta::v1::range'
class range {
      ^
/Users/sam/work/new-build/lib/clang/9.0.0/include/experimental/meta:957:12: note: 
      implicitly declared private here
  iterator m_last;
           ^
wyattproblem.cpp:46:32: error: no viable conversion from 'const
      std::experimental::meta::v1::iterator' to 'const meta::info'
  for... (constexpr meta::info member : range) {
                               ^
wyattproblem.cpp:61:33: error: constexpr variable 'result' must be initialized
      by a constant expression
  constexpr meta::info result = get_fib<foo, 1>();
                                ^~~~~~~~~~~~~~~~~
12 errors generated.

[l3bot]

In GitLab by @DarkArc on Jul 11, 2019, 13:47

Still a problem here, we shouldn't be seeing these errors:

../clang/test/CXX/meta/scratch.cpp:46:41: error: constexpr variable '__range' must be initialized by a constant expression
  for... (constexpr meta::info member : range) {
                                        ^~~~~
../clang/test/CXX/meta/scratch.cpp:61:33: note: in instantiation of function template specialization 'get_fib<foo, 1>' requested here
  constexpr meta::info result = get_fib<foo, 1>();
                                ^
../clang/test/CXX/meta/scratch.cpp:46:41: note: reference to 'range' is not a constant expression
  for... (constexpr meta::info member : range) {
                                        ^
../clang/test/CXX/meta/scratch.cpp:44:18: note: declared here
  constexpr auto range = meta::range(reflexpr(container_type));
                 ^
../clang/test/CXX/meta/scratch.cpp:46:39: error: constexpr variable '__begin' must be initialized by a constant expression
  for... (constexpr meta::info member : range) {
                                      ^
../clang/test/CXX/meta/scratch.cpp:46:39: note: initializer of '__range' is not a constant expression
../clang/test/CXX/meta/scratch.cpp:46:41: note: declared here
  for... (constexpr meta::info member : range) {
                                        ^
../clang/test/CXX/meta/scratch.cpp:46:39: error: constexpr variable '__end' must be initialized by a constant expression
  for... (constexpr meta::info member : range) {
                                      ^
../clang/test/CXX/meta/scratch.cpp:46:39: note: initializer of '__range' is not a constant expression
../clang/test/CXX/meta/scratch.cpp:46:41: note: declared here
  for... (constexpr meta::info member : range) {
                                        ^

For posterity, the previously reported backtrace was a backtrace AFTER attempting to change the behavior of auto vs auto &&.

[l3bot]

In GitLab by @DarkArc on Jul 11, 2019, 13:50

Updated simplified test code:

#include <experimental/meta>

using namespace std::experimental;

template<typename container_type, int target_index>
static constexpr meta::info get_fib() {
  constexpr const char* target_name = __concatenate("fib_", target_index);
  constexpr auto range = meta::range(reflexpr(container_type));

  for... (constexpr meta::info member : range) {
    if (meta::name_of(member) == target_name)
      return member;
  }

  return meta::info();
}

class foo {
  constexpr static int fib_0 = 0;
  constexpr static int fib_1 = 1;
  constexpr static int fib_2 = 1;
};

int main() {
  constexpr meta::info result = get_fib<foo, 1>();
  return 0;
}

[l3bot]

In GitLab by @sdgoodrick on Jul 12, 2019, 11:52

Right now the current issue is that initializing a variable with the return of a constexpr function that has an expansion statement crashes.

Example: Working program:

template <typename Container>
constexpr meta::info foo() {
  constexpr std::experimental::meta::range v = {reflexpr(Container)};
  for... (constexpr auto x : v)
     ;
  return meta::info();
}

struct S {
  int a;
  int b;
  int c;
};

int main()
{
  foo<S>();
}

Crashing program:

template <typename Container>
constexpr meta::info foo() {
  constexpr std::experimental::meta::range v = {reflexpr(Container)};
  for... (constexpr auto x : v)
    ;
  return meta::info();
}

struct S {
  int a;
  int b;
  int c;
};

int main()
{
  constexpr meta::info x = foo<S>(); // only difference
}

[l3bot]

In GitLab by @DarkArc on Aug 28, 2019, 17:57

Fixed in abd095d1e9191c64627924a620fa967f1ab0f454.

[l3bot]

In GitLab by @DarkArc on Aug 28, 2019, 17:57

closed