ICE in forward from deduced this in lambda

[rollbear]

Huge thanks for landing P0847R7 in clang.

This short snippet crashes clang built from f58d54a

#include <utility>

auto f = [x = 3]<typename Self>(this Self&& self)
  {
    return std::forward_like<Self>(x);
  };

int main()
{
  return std::move(f)();
}

bf@pteranodon /tmp > /opt/llvm-p0847r7/bin/clang++ -std=c++2c /tmp/t.cpp -stdlib=libc++
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace, preprocessed source, and associated run script.
Stack dump:
0.      Program arguments: /opt/llvm-p0847r7/bin/clang-18 -cc1 -triple x86_64-unknown-linux-gnu -emit-obj -mrelax-all -dumpdir a- -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name t.cpp -mrelocation-model pic -pic-level 2 -pic-is-pie -mframe-pointer=all -fmath-errno -ffp-contract=on -fno-rounding-math -mconstructor-aliases -funwind-tables=2 -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb -fdebug-compilation-dir=/tmp -fcoverage-compilation-dir=/tmp -resource-dir /opt/llvm-p0847r7/lib/clang/18 -internal-isystem /opt/llvm-p0847r7/bin/../include/x86_64-unknown-linux-gnu/c++/v1 -internal-isystem /opt/llvm-p0847r7/bin/../include/c++/v1 -internal-isystem /opt/llvm-p0847r7/lib/clang/18/include -internal-isystem /usr/local/include -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/13/../../../../x86_64-linux-gnu/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -std=c++2c -fdeprecated-macro -ferror-limit 19 -fgnuc-version=4.2.1 -fno-implicit-modules -fcxx-exceptions -fexceptions -fcolor-diagnostics -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /tmp/t-442d5d.o -x c++ /tmp/t.cpp
1.      <eof> parser at end of file
2.      /tmp/t.cpp:8:5: LLVM IR generation of declaration 'main'
3.      /tmp/t.cpp:8:5: Generating code for declaration 'main'
 #0 0x0000558ec0661ef2 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/llvm-p0847r7/bin/clang-18+0x3621ef2)
 #1 0x0000558ec065f37b SignalHandler(int) Signals.cpp:0:0
 #2 0x00007f5494e3c4b0 (/lib/x86_64-linux-gnu/libc.so.6+0x3c4b0)
 #3 0x0000558ec359a919 (anonymous namespace)::LValueExprEvaluator::VisitVarDecl(clang::Expr const*, clang::VarDecl const*) ExprConstant.cpp:0:0
 #4 0x0000558ec35d9bf8 (anonymous namespace)::IntExprEvaluator::VisitCastExpr(clang::CastExpr const*) ExprConstant.cpp:0:0
 #5 0x0000558ec35920a0 Evaluate(clang::APValue&, (anonymous namespace)::EvalInfo&, clang::Expr const*) ExprConstant.cpp:0:0
 #6 0x0000558ec35ab61d EvaluateStmt((anonymous namespace)::StmtResult&, (anonymous namespace)::EvalInfo&, clang::Stmt const*, clang::SwitchCase const*) ExprConstant.cpp:0:0
 #7 0x0000558ec35aaaaf EvaluateStmt((anonymous namespace)::StmtResult&, (anonymous namespace)::EvalInfo&, clang::Stmt const*, clang::SwitchCase const*) ExprConstant.cpp:0:0
 #8 0x0000558ec35b2a38 HandleFunctionCall(clang::SourceLocation, clang::FunctionDecl const*, (anonymous namespace)::LValue const*, clang::Expr const*, llvm::ArrayRef<clang::Expr const*>, (anonymous namespace)::CallRef, clang::Stmt const*, (anonymous namespace)::EvalInfo&, clang::APValue&, (anonymous namespace)::LValue const*) (.isra.0) ExprConstant.cpp:0:0
 #9 0x0000558ec35e056f (anonymous namespace)::IntExprEvaluator::VisitCallExpr(clang::CallExpr const*) ExprConstant.cpp:0:0
#10 0x0000558ec35920a0 Evaluate(clang::APValue&, (anonymous namespace)::EvalInfo&, clang::Expr const*) ExprConstant.cpp:0:0
#11 0x0000558ec359b478 EvaluateAsRValue((anonymous namespace)::EvalInfo&, clang::Expr const*, clang::APValue&) ExprConstant.cpp:0:0
#12 0x0000558ec359cdc9 clang::Expr::EvaluateAsRValue(clang::Expr::EvalResult&, clang::ASTContext const&, bool) const (/opt/llvm-p0847r7/bin/clang-18+0x655cdc9)
#13 0x0000558ec359cf26 clang::Expr::isEvaluatable(clang::ASTContext const&, clang::Expr::SideEffectsKind) const (/opt/llvm-p0847r7/bin/clang-18+0x655cf26)
#14 0x0000558ec0932f5d clang::CodeGen::CodeGenFunction::EmitReturnStmt(clang::ReturnStmt const&) (/opt/llvm-p0847r7/bin/clang-18+0x38f2f5d)
#15 0x0000558ec0940629 clang::CodeGen::CodeGenFunction::EmitCompoundStmtWithoutScope(clang::CompoundStmt const&, bool, clang::CodeGen::AggValueSlot) (/opt/llvm-p0847r7/bin/clang-18+0x3900629)
#16 0x0000558ec099979b clang::CodeGen::CodeGenFunction::EmitFunctionBody(clang::Stmt const*) (/opt/llvm-p0847r7/bin/clang-18+0x395979b)
#17 0x0000558ec09ab3d5 clang::CodeGen::CodeGenFunction::GenerateCode(clang::GlobalDecl, llvm::Function*, clang::CodeGen::CGFunctionInfo const&) (/opt/llvm-p0847r7/bin/clang-18+0x396b3d5)
#18 0x0000558ec09f4b9a clang::CodeGen::CodeGenModule::EmitGlobalFunctionDefinition(clang::GlobalDecl, llvm::GlobalValue*) (/opt/llvm-p0847r7/bin/clang-18+0x39b4b9a)
#19 0x0000558ec09f0b6c clang::CodeGen::CodeGenModule::EmitGlobalDefinition(clang::GlobalDecl, llvm::GlobalValue*) (/opt/llvm-p0847r7/bin/clang-18+0x39b0b6c)
#20 0x0000558ec09f1263 clang::CodeGen::CodeGenModule::EmitGlobal(clang::GlobalDecl) (/opt/llvm-p0847r7/bin/clang-18+0x39b1263)
#21 0x0000558ec09f7dd7 clang::CodeGen::CodeGenModule::EmitTopLevelDecl(clang::Decl*) (.part.0) CodeGenModule.cpp:0:0
#22 0x0000558ec180a238 (anonymous namespace)::CodeGeneratorImpl::HandleTopLevelDecl(clang::DeclGroupRef) ModuleBuilder.cpp:0:0
#23 0x0000558ec17fac77 clang::BackendConsumer::HandleTopLevelDecl(clang::DeclGroupRef) (/opt/llvm-p0847r7/bin/clang-18+0x47bac77)
#24 0x0000558ec2641304 clang::ParseAST(clang::Sema&, bool, bool) (/opt/llvm-p0847r7/bin/clang-18+0x5601304)
#25 0x0000558ec10e1a49 clang::FrontendAction::Execute() (/opt/llvm-p0847r7/bin/clang-18+0x40a1a49)
#26 0x0000558ec1065fb9 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/llvm-p0847r7/bin/clang-18+0x4025fb9)
#27 0x0000558ec11a581b clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/llvm-p0847r7/bin/clang-18+0x416581b)
#28 0x0000558ebde1c481 cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/llvm-p0847r7/bin/clang-18+0xddc481)
#29 0x0000558ebde14e0a ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#30 0x0000558ebde18c91 clang_main(int, char**, llvm::ToolContext const&) (/opt/llvm-p0847r7/bin/clang-18+0xdd8c91)
#31 0x0000558ebdd1ab33 main (/opt/llvm-p0847r7/bin/clang-18+0xcdab33)
#32 0x00007f5494e23a90 __libc_start_call_main ./csu/../sysdeps/nptl/libc_start_call_main.h:74:3
#33 0x00007f5494e23b49 call_init ./csu/../csu/libc-start.c:128:20
#34 0x00007f5494e23b49 __libc_start_main ./csu/../csu/libc-start.c:347:5
#35 0x0000558ebde14285 _start (/opt/llvm-p0847r7/bin/clang-18+0xdd4285)
clang++: error: unable to execute command: Segmentation fault (core dumped)
clang++: error: clang frontend command failed due to signal (use -v to see invocation)
clang version 18.0.0 (https://github.com/llvm/llvm-project f58d54ab969b2f342a882dfb03334f18f4ec1dcc)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /opt/llvm-p0847r7/bin
clang++: note: diagnostic msg: 
********************

PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
Preprocessed source(s) and associated run script(s) are located at:
clang++: note: diagnostic msg: /tmp/t-4a6752.cpp
clang++: note: diagnostic msg: /tmp/t-4a6752.sh
clang++: note: diagnostic msg: 

********************

The synonymous construction from a hand written type does not cause a crash.

#include <utility>

struct S
{
  int x = 3;
  template <typename Self>
  auto operator()(this Self&& self)
  {
    return std::forward_like<Self>(self.x);
  }
};


int main()
{
  S s;
  return std::move(s)();
}

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Huge thanks for landing P0847R7 in clang.

This short snippet crashes clang built from f58d54a

#include <utility>

auto f = [x = 3]<typename Self>(this Self&& self)
  {
    return std::forward_like<Self>(x);
  };

int main()
{
  return std::move(f)();
}

bf@<!-- -->pteranodon /tmp &gt; /opt/llvm-p0847r7/bin/clang++ -std=c++2c /tmp/t.cpp -stdlib=libc++
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace, preprocessed source, and associated run script.
Stack dump:
0.      Program arguments: /opt/llvm-p0847r7/bin/clang-18 -cc1 -triple x86_64-unknown-linux-gnu -emit-obj -mrelax-all -dumpdir a- -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name t.cpp -mrelocation-model pic -pic-level 2 -pic-is-pie -mframe-pointer=all -fmath-errno -ffp-contract=on -fno-rounding-math -mconstructor-aliases -funwind-tables=2 -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb -fdebug-compilation-dir=/tmp -fcoverage-compilation-dir=/tmp -resource-dir /opt/llvm-p0847r7/lib/clang/18 -internal-isystem /opt/llvm-p0847r7/bin/../include/x86_64-unknown-linux-gnu/c++/v1 -internal-isystem /opt/llvm-p0847r7/bin/../include/c++/v1 -internal-isystem /opt/llvm-p0847r7/lib/clang/18/include -internal-isystem /usr/local/include -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/13/../../../../x86_64-linux-gnu/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -std=c++2c -fdeprecated-macro -ferror-limit 19 -fgnuc-version=4.2.1 -fno-implicit-modules -fcxx-exceptions -fexceptions -fcolor-diagnostics -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /tmp/t-442d5d.o -x c++ /tmp/t.cpp
1.      &lt;eof&gt; parser at end of file
2.      /tmp/t.cpp:8:5: LLVM IR generation of declaration 'main'
3.      /tmp/t.cpp:8:5: Generating code for declaration 'main'
 #<!-- -->0 0x0000558ec0661ef2 llvm::sys::PrintStackTrace(llvm::raw_ostream&amp;, int) (/opt/llvm-p0847r7/bin/clang-18+0x3621ef2)
 #<!-- -->1 0x0000558ec065f37b SignalHandler(int) Signals.cpp:0:0
 #<!-- -->2 0x00007f5494e3c4b0 (/lib/x86_64-linux-gnu/libc.so.6+0x3c4b0)
 #<!-- -->3 0x0000558ec359a919 (anonymous namespace)::LValueExprEvaluator::VisitVarDecl(clang::Expr const*, clang::VarDecl const*) ExprConstant.cpp:0:0
 #<!-- -->4 0x0000558ec35d9bf8 (anonymous namespace)::IntExprEvaluator::VisitCastExpr(clang::CastExpr const*) ExprConstant.cpp:0:0
 #<!-- -->5 0x0000558ec35920a0 Evaluate(clang::APValue&amp;, (anonymous namespace)::EvalInfo&amp;, clang::Expr const*) ExprConstant.cpp:0:0
 #<!-- -->6 0x0000558ec35ab61d EvaluateStmt((anonymous namespace)::StmtResult&amp;, (anonymous namespace)::EvalInfo&amp;, clang::Stmt const*, clang::SwitchCase const*) ExprConstant.cpp:0:0
 #<!-- -->7 0x0000558ec35aaaaf EvaluateStmt((anonymous namespace)::StmtResult&amp;, (anonymous namespace)::EvalInfo&amp;, clang::Stmt const*, clang::SwitchCase const*) ExprConstant.cpp:0:0
 #<!-- -->8 0x0000558ec35b2a38 HandleFunctionCall(clang::SourceLocation, clang::FunctionDecl const*, (anonymous namespace)::LValue const*, clang::Expr const*, llvm::ArrayRef&lt;clang::Expr const*&gt;, (anonymous namespace)::CallRef, clang::Stmt const*, (anonymous namespace)::EvalInfo&amp;, clang::APValue&amp;, (anonymous namespace)::LValue const*) (.isra.0) ExprConstant.cpp:0:0
 #<!-- -->9 0x0000558ec35e056f (anonymous namespace)::IntExprEvaluator::VisitCallExpr(clang::CallExpr const*) ExprConstant.cpp:0:0
#<!-- -->10 0x0000558ec35920a0 Evaluate(clang::APValue&amp;, (anonymous namespace)::EvalInfo&amp;, clang::Expr const*) ExprConstant.cpp:0:0
#<!-- -->11 0x0000558ec359b478 EvaluateAsRValue((anonymous namespace)::EvalInfo&amp;, clang::Expr const*, clang::APValue&amp;) ExprConstant.cpp:0:0
#<!-- -->12 0x0000558ec359cdc9 clang::Expr::EvaluateAsRValue(clang::Expr::EvalResult&amp;, clang::ASTContext const&amp;, bool) const (/opt/llvm-p0847r7/bin/clang-18+0x655cdc9)
#<!-- -->13 0x0000558ec359cf26 clang::Expr::isEvaluatable(clang::ASTContext const&amp;, clang::Expr::SideEffectsKind) const (/opt/llvm-p0847r7/bin/clang-18+0x655cf26)
#<!-- -->14 0x0000558ec0932f5d clang::CodeGen::CodeGenFunction::EmitReturnStmt(clang::ReturnStmt const&amp;) (/opt/llvm-p0847r7/bin/clang-18+0x38f2f5d)
#<!-- -->15 0x0000558ec0940629 clang::CodeGen::CodeGenFunction::EmitCompoundStmtWithoutScope(clang::CompoundStmt const&amp;, bool, clang::CodeGen::AggValueSlot) (/opt/llvm-p0847r7/bin/clang-18+0x3900629)
#<!-- -->16 0x0000558ec099979b clang::CodeGen::CodeGenFunction::EmitFunctionBody(clang::Stmt const*) (/opt/llvm-p0847r7/bin/clang-18+0x395979b)
#<!-- -->17 0x0000558ec09ab3d5 clang::CodeGen::CodeGenFunction::GenerateCode(clang::GlobalDecl, llvm::Function*, clang::CodeGen::CGFunctionInfo const&amp;) (/opt/llvm-p0847r7/bin/clang-18+0x396b3d5)
#<!-- -->18 0x0000558ec09f4b9a clang::CodeGen::CodeGenModule::EmitGlobalFunctionDefinition(clang::GlobalDecl, llvm::GlobalValue*) (/opt/llvm-p0847r7/bin/clang-18+0x39b4b9a)
#<!-- -->19 0x0000558ec09f0b6c clang::CodeGen::CodeGenModule::EmitGlobalDefinition(clang::GlobalDecl, llvm::GlobalValue*) (/opt/llvm-p0847r7/bin/clang-18+0x39b0b6c)
#<!-- -->20 0x0000558ec09f1263 clang::CodeGen::CodeGenModule::EmitGlobal(clang::GlobalDecl) (/opt/llvm-p0847r7/bin/clang-18+0x39b1263)
#<!-- -->21 0x0000558ec09f7dd7 clang::CodeGen::CodeGenModule::EmitTopLevelDecl(clang::Decl*) (.part.0) CodeGenModule.cpp:0:0
#<!-- -->22 0x0000558ec180a238 (anonymous namespace)::CodeGeneratorImpl::HandleTopLevelDecl(clang::DeclGroupRef) ModuleBuilder.cpp:0:0
#<!-- -->23 0x0000558ec17fac77 clang::BackendConsumer::HandleTopLevelDecl(clang::DeclGroupRef) (/opt/llvm-p0847r7/bin/clang-18+0x47bac77)
#<!-- -->24 0x0000558ec2641304 clang::ParseAST(clang::Sema&amp;, bool, bool) (/opt/llvm-p0847r7/bin/clang-18+0x5601304)
#<!-- -->25 0x0000558ec10e1a49 clang::FrontendAction::Execute() (/opt/llvm-p0847r7/bin/clang-18+0x40a1a49)
#<!-- -->26 0x0000558ec1065fb9 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&amp;) (/opt/llvm-p0847r7/bin/clang-18+0x4025fb9)
#<!-- -->27 0x0000558ec11a581b clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/llvm-p0847r7/bin/clang-18+0x416581b)
#<!-- -->28 0x0000558ebde1c481 cc1_main(llvm::ArrayRef&lt;char const*&gt;, char const*, void*) (/opt/llvm-p0847r7/bin/clang-18+0xddc481)
#<!-- -->29 0x0000558ebde14e0a ExecuteCC1Tool(llvm::SmallVectorImpl&lt;char const*&gt;&amp;, llvm::ToolContext const&amp;) driver.cpp:0:0
#<!-- -->30 0x0000558ebde18c91 clang_main(int, char**, llvm::ToolContext const&amp;) (/opt/llvm-p0847r7/bin/clang-18+0xdd8c91)
#<!-- -->31 0x0000558ebdd1ab33 main (/opt/llvm-p0847r7/bin/clang-18+0xcdab33)
#<!-- -->32 0x00007f5494e23a90 __libc_start_call_main ./csu/../sysdeps/nptl/libc_start_call_main.h:74:3
#<!-- -->33 0x00007f5494e23b49 call_init ./csu/../csu/libc-start.c:128:20
#<!-- -->34 0x00007f5494e23b49 __libc_start_main ./csu/../csu/libc-start.c:347:5
#<!-- -->35 0x0000558ebde14285 _start (/opt/llvm-p0847r7/bin/clang-18+0xdd4285)
clang++: error: unable to execute command: Segmentation fault (core dumped)
clang++: error: clang frontend command failed due to signal (use -v to see invocation)
clang version 18.0.0 (https://github.com/llvm/llvm-project f58d54ab969b2f342a882dfb03334f18f4ec1dcc)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /opt/llvm-p0847r7/bin
clang++: note: diagnostic msg: 
********************

PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
Preprocessed source(s) and associated run script(s) are located at:
clang++: note: diagnostic msg: /tmp/t-4a6752.cpp
clang++: note: diagnostic msg: /tmp/t-4a6752.sh
clang++: note: diagnostic msg: 

********************

The synonymous construction from a hand written type does not cause a crash.

#include <utility>

struct S
{
  int x = 3;
  template <typename Self>
  auto operator()(this Self&& self)
  {
    return std::forward_like<Self>(self.x);
  }
};


int main()
{
  S s;
  return std::move(s)();
}

[tbaederr]

Looks like the constant expression evaluator expects a non-null This, but it's null:

#4: ExprConstant.cpp:8370  (anonymous namespace)::LValueExprEvaluator::VisitVarDecl(this=0x00007fff6daafe80, E=0x000062d00029a538, VD=0x000062d000299f70)
   8367	
   8368	    if (auto *FD = Info.CurrentCall->LambdaCaptureFields.lookup(VD)) {
   8369	      // Start with 'Result' referring to the complete closure object...
-> 8370	      Result = *Info.CurrentCall->This;
   8371	      // ... then update it to refer to the field of the closure object
   8372	      // that represents the capture.
   8373	      if (!HandleLValueMember(Info, E, Result, FD))
(lldb) p Info.CurrentCall
(CallStackFrame *) $1 = 0x00007fff6dcb2880
(lldb) p Info.CurrentCall->This
(const LValue *) $2 = nullptr
(lldb)

[rollbear]

Awesome @cor3ntin, thank you!

[cor3ntin]

Any time! Thanks for trying deducing this. Please let us know if you find more bugs, the implementation is fresh out of the oven and it might take us some time to flesh it out.