[clangd] "Expected valid TemplateArgument" for `std::min`-like template #139019

tbaederr · 2025-05-08T04:13:17Z

For these two files:

// test.cpp
#include "test.h"

void run(int num_total_tasks) {
  int cnt{};
  int x;

  for (int i = 0; i < min(x, num_total_tas - cnt); ++i) {}
}

// test.h
template<typename T>
T min(T A, T B) { return A < B ? A : B; }

bin/clangd --check=test.cpp --check-completion crashes:

Expected valid TemplateArgument
UNREACHABLE executed at /home/tbaeder/code/llvm-project/clang/lib/Serialization/TemplateArgumentHasher.cpp:68!
Process 3542402 stopped
* thread #1, name = 'clangd', stop reason = signal SIGABRT
    frame #0: 0x00007fff8287ff54 libc.so.6`__pthread_kill_implementation + 276
libc.so.6`__pthread_kill_implementation:
->  0x7fff8287ff54 <+276>: movl   %eax, %ebx
    0x7fff8287ff56 <+278>: negl   %ebx
    0x7fff8287ff58 <+280>: cmpl   $0xfffff000, %eax ; imm = 0xFFFFF000
    0x7fff8287ff5d <+285>: movl   $0x0, %eax
(lldb) bt
* thread #1, name = 'clangd', stop reason = signal SIGABRT
  * frame #0: 0x00007fff8287ff54 libc.so.6`__pthread_kill_implementation + 276
    frame #1: 0x00007fff82826f9e libc.so.6`raise + 30
    frame #2: 0x00007fff8280e942 libc.so.6`abort + 223
    frame #3: 0x00007fffa25151d5 libLLVM.so.21.0git`llvm::llvm_unreachable_internal(msg="Expected valid TemplateArgument", file="/home/tbaeder/code/llvm-project/clang/lib/Serialization/TemplateArgumentHasher.cpp", line=68) at ErrorHandling.cpp:233:3
    frame #4: 0x00007fffe8b473c9 libclang-cpp.so.21.0git`(anonymous namespace)::TemplateArgumentHasher::AddTemplateArgument(this=0x00007bff808b3e40, TA=TemplateArgument @ 0x00007bff8071a720) at TemplateArgumentHasher.cpp:68:5
    frame #5: 0x00007fffe8b46f3c libclang-cpp.so.21.0git`clang::serialization::StableHashForTemplateArguments(Args=ArrayRef<clang::TemplateArgument> @ 0x00007bff808b3e20) at TemplateArgumentHasher.cpp:409:12
    frame #6: 0x00007fffe83b71f0 libclang-cpp.so.21.0git`clang::ASTReader::LoadExternalSpecializationsImpl(this=0x00007e8f8218d200, SpecLookups=0x00007e8f8218e188, D=0x00007e0f841bb1e8, TemplateArgs=ArrayRef<clang::TemplateArgument> @ 0x00007ffffffe0d30) at ASTReader.cpp:8388:20
    frame #7: 0x00007fffe83b77b3 libclang-cpp.so.21.0git`clang::ASTReader::LoadExternalSpecializations(this=0x00007e8f8218d200, D=0x00007e0f841bb1e8, TemplateArgs=ArrayRef<clang::TemplateArgument> @ 0x00007ffffffe0e00) at ASTReader.cpp:8412:7
    frame #8: 0x00007fffdd9eae82 libclang-cpp.so.21.0git`clang::RedeclarableTemplateDecl::loadLazySpecializationsImpl(this=0x00007e0f841bb1e8, Args=ArrayRef<clang::TemplateArgument> @ 0x00007ffffffe0ea8, TPL=0x0000000000000000) const at DeclTemplate.cpp:377:26
    frame #9: 0x00007fffdda040e8 libclang-cpp.so.21.0git`clang::RedeclarableTemplateDecl::SpecEntryTraits<clang::FunctionTemplateSpecializationInfo>::DeclType* clang::RedeclarableTemplateDecl::findSpecializationImpl<clang::FunctionTemplateSpecializationInfo, llvm::ArrayRef<clang::TemplateArgument>&>(this=0x00007e0f841bb1e8, Specs=0x00007e0f841bb250, InsertPos=0x00007bff80bd9040, ProfileArgs=0x00007bff805c8f20) at DeclTemplate.cpp:405:8
    frame #10: 0x00007fffdd9eba3d libclang-cpp.so.21.0git`clang::FunctionTemplateDecl::findSpecialization(this=0x00007e0f841bb1e8, Args=ArrayRef<clang::TemplateArgument> @ 0x00007bff805c8f20, InsertPos=0x00007bff80bd9040) at DeclTemplate.cpp:487:10
    frame #11: 0x00007fffe405c00c libclang-cpp.so.21.0git`clang::TemplateDeclInstantiator::VisitFunctionDecl(this=0x00007bff808b3840, D=0x00007e0f841bb3c8, TemplateParams=0x0000000000000000, FunctionRewriteKind=None) at SemaTemplateInstantiateDecl.cpp:2623:27
    frame #12: 0x00007fffe407cf13 libclang-cpp.so.21.0git`clang::TemplateDeclInstantiator::VisitFunctionDecl(this=0x00007bff808b3840, D=0x00007e0f841bb3c8) at SemaTemplateInstantiateDecl.cpp:4343:10
    frame #13: 0x00007fffe3fe94b0 libclang-cpp.so.21.0git`clang::declvisitor::Base<std::add_pointer, clang::TemplateDeclInstantiator, clang::Decl*>::Visit(this=0x00007bff808b3840, D=0x00007e0f841bb3c8) at DeclNodes.inc:256:1
    frame #14: 0x00007fffe4223810 libclang-cpp.so.21.0git`clang::Sema::SubstDecl(clang::Decl*, clang::DeclContext*, clang::MultiLevelTemplateArgumentList const&)::$_0::operator()(this=0x00007bff808b39a0) const at SemaTemplateInstantiateDecl.cpp:4616:27
    frame #15: 0x00007fffe4223715 libclang-cpp.so.21.0git`void llvm::function_ref<void ()>::callback_fn<clang::Sema::SubstDecl(clang::Decl*, clang::DeclContext*, clang::MultiLevelTemplateArgumentList const&)::$_0>(callable=136337303484832) at STLFunctionalExtras.h:46:12
    frame #16: 0x00007fffdb93ae2c libclang-cpp.so.21.0git`llvm::function_ref<void ()>::operator()(this=0x00007bff805c8de0) const at STLFunctionalExtras.h:69:12
    frame #17: 0x00007fffdb93b6a5 libclang-cpp.so.21.0git`clang::runWithSufficientStackSpace(Diag=function_ref<void ()> @ 0x00007ffffffe21b8, Fn=function_ref<void ()> @ 0x00007bff805c8de0) at Stack.h:49:7
    frame #18: 0x00007fffdb93b00c libclang-cpp.so.21.0git`clang::StackExhaustionHandler::runWithSufficientStackSpace(this=0x00007e8f82192460, Loc=(ID = 2147483606), Fn=function_ref<void ()> @ 0x00007ffffffe22b8) at StackExhaustionHandler.cpp:20:3
    frame #19: 0x00007fffe09b87a6 libclang-cpp.so.21.0git`clang::Sema::runWithSufficientStackSpace(this=0x00007e8f82192200, Loc=(ID = 2147483606), Fn=function_ref<void ()> @ 0x00007ffffffe2338) at Sema.cpp:606:16
    frame #20: 0x00007fffe4081b2e libclang-cpp.so.21.0git`clang::Sema::SubstDecl(this=0x00007e8f82192200, D=0x00007e0f841bb3c8, Owner=0x00007e0f841b6d30, TemplateArgs=0x00007bff80a8bb40) at SemaTemplateInstantiateDecl.cpp:4615:3
    frame #21: 0x00007fffe3a68a1d libclang-cpp.so.21.0git`clang::Sema::FinishTemplateArgumentDeduction(this=0x00007e8f82192200, FunctionTemplate=0x00007e0f841bb1e8, Deduced=0x00007bff80bd8220, NumExplicitlySpecified=0, Specialization=0x00007bff80a8b2e0, Info=0x00007bff80a8b0a0, OriginalCallArgs=0x00007bff80bd8400, PartialOverloading=true, PartialOrdering=false, CheckNonDependent=function_ref<bool ()> @ 0x00007bff80a8b820) at SemaTemplateDeduction.cpp:3947:7

The template argument is:

(clang::TemplateArgument) {
   = {
    DeclArg = {
      Kind = Null
      IsDefaulted = false
      QT = 0x0000000000000000
      D = 0x00007fffd22b2140
    }
    Integer = {
      Kind = Null
      IsDefaulted = false
      BitWidth = 32766
      IsUnsigned = false
       = {
        VAL = 0
        pVal = 0x0000000000000000
      }
      Type = 0x00007fffd22b2140
    }
    Value = {
      Kind = Null
      IsDefaulted = false
      Value = nullptr
      Type = 0x00007fffd22b2140
    }
    Args = {
      Kind = Null
      IsDefaulted = false
      NumArgs = 32766
      Args = nullptr
    }
    TemplateArg = {
      Kind = Null
      IsDefaulted = false
      NumExpansions = (Rep = 32766)
      Name = 0x0000000000000000
    }
    TypeOrValue = (Kind = Null, IsDefaulted = false, IsCanonicalExpr = false, V = 0)
  }
}

The text was updated successfully, but these errors were encountered:

llvmbot · 2025-05-08T04:13:36Z

@llvm/issue-subscribers-clangd

Author: Timm Baeder (tbaederr)

For these two files: ```c++ // test.cpp #include "test.h"

void run(int num_total_tasks) {
int cnt{};
int x;

for (int i = 0; i < min(x, num_total_tas - cnt); ++i) {}
}


```c++
// test.h
template&lt;typename T&gt;
T min(T A, T B) { return A &lt; B ? A : B; }

bin/clangd --check=test.cpp --check-completion crashes:

Expected valid TemplateArgument
UNREACHABLE executed at /home/tbaeder/code/llvm-project/clang/lib/Serialization/TemplateArgumentHasher.cpp:68!
Process 3542402 stopped
* thread #<!-- -->1, name = 'clangd', stop reason = signal SIGABRT
    frame #<!-- -->0: 0x00007fff8287ff54 libc.so.6`__pthread_kill_implementation + 276
libc.so.6`__pthread_kill_implementation:
-&gt;  0x7fff8287ff54 &lt;+276&gt;: movl   %eax, %ebx
    0x7fff8287ff56 &lt;+278&gt;: negl   %ebx
    0x7fff8287ff58 &lt;+280&gt;: cmpl   $0xfffff000, %eax ; imm = 0xFFFFF000
    0x7fff8287ff5d &lt;+285&gt;: movl   $0x0, %eax
(lldb) bt
* thread #<!-- -->1, name = 'clangd', stop reason = signal SIGABRT
  * frame #<!-- -->0: 0x00007fff8287ff54 libc.so.6`__pthread_kill_implementation + 276
    frame #<!-- -->1: 0x00007fff82826f9e libc.so.6`raise + 30
    frame #<!-- -->2: 0x00007fff8280e942 libc.so.6`abort + 223
    frame #<!-- -->3: 0x00007fffa25151d5 libLLVM.so.21.0git`llvm::llvm_unreachable_internal(msg="Expected valid TemplateArgument", file="/home/tbaeder/code/llvm-project/clang/lib/Serialization/TemplateArgumentHasher.cpp", line=68) at ErrorHandling.cpp:233:3
    frame #<!-- -->4: 0x00007fffe8b473c9 libclang-cpp.so.21.0git`(anonymous namespace)::TemplateArgumentHasher::AddTemplateArgument(this=0x00007bff808b3e40, TA=TemplateArgument @ 0x00007bff8071a720) at TemplateArgumentHasher.cpp:68:5
    frame #<!-- -->5: 0x00007fffe8b46f3c libclang-cpp.so.21.0git`clang::serialization::StableHashForTemplateArguments(Args=ArrayRef&lt;clang::TemplateArgument&gt; @ 0x00007bff808b3e20) at TemplateArgumentHasher.cpp:409:12
    frame #<!-- -->6: 0x00007fffe83b71f0 libclang-cpp.so.21.0git`clang::ASTReader::LoadExternalSpecializationsImpl(this=0x00007e8f8218d200, SpecLookups=0x00007e8f8218e188, D=0x00007e0f841bb1e8, TemplateArgs=ArrayRef&lt;clang::TemplateArgument&gt; @ 0x00007ffffffe0d30) at ASTReader.cpp:8388:20
    frame #<!-- -->7: 0x00007fffe83b77b3 libclang-cpp.so.21.0git`clang::ASTReader::LoadExternalSpecializations(this=0x00007e8f8218d200, D=0x00007e0f841bb1e8, TemplateArgs=ArrayRef&lt;clang::TemplateArgument&gt; @ 0x00007ffffffe0e00) at ASTReader.cpp:8412:7
    frame #<!-- -->8: 0x00007fffdd9eae82 libclang-cpp.so.21.0git`clang::RedeclarableTemplateDecl::loadLazySpecializationsImpl(this=0x00007e0f841bb1e8, Args=ArrayRef&lt;clang::TemplateArgument&gt; @ 0x00007ffffffe0ea8, TPL=0x0000000000000000) const at DeclTemplate.cpp:377:26
    frame #<!-- -->9: 0x00007fffdda040e8 libclang-cpp.so.21.0git`clang::RedeclarableTemplateDecl::SpecEntryTraits&lt;clang::FunctionTemplateSpecializationInfo&gt;::DeclType* clang::RedeclarableTemplateDecl::findSpecializationImpl&lt;clang::FunctionTemplateSpecializationInfo, llvm::ArrayRef&lt;clang::TemplateArgument&gt;&amp;&gt;(this=0x00007e0f841bb1e8, Specs=0x00007e0f841bb250, InsertPos=0x00007bff80bd9040, ProfileArgs=0x00007bff805c8f20) at DeclTemplate.cpp:405:8
    frame #<!-- -->10: 0x00007fffdd9eba3d libclang-cpp.so.21.0git`clang::FunctionTemplateDecl::findSpecialization(this=0x00007e0f841bb1e8, Args=ArrayRef&lt;clang::TemplateArgument&gt; @ 0x00007bff805c8f20, InsertPos=0x00007bff80bd9040) at DeclTemplate.cpp:487:10
    frame #<!-- -->11: 0x00007fffe405c00c libclang-cpp.so.21.0git`clang::TemplateDeclInstantiator::VisitFunctionDecl(this=0x00007bff808b3840, D=0x00007e0f841bb3c8, TemplateParams=0x0000000000000000, FunctionRewriteKind=None) at SemaTemplateInstantiateDecl.cpp:2623:27
    frame #<!-- -->12: 0x00007fffe407cf13 libclang-cpp.so.21.0git`clang::TemplateDeclInstantiator::VisitFunctionDecl(this=0x00007bff808b3840, D=0x00007e0f841bb3c8) at SemaTemplateInstantiateDecl.cpp:4343:10
    frame #<!-- -->13: 0x00007fffe3fe94b0 libclang-cpp.so.21.0git`clang::declvisitor::Base&lt;std::add_pointer, clang::TemplateDeclInstantiator, clang::Decl*&gt;::Visit(this=0x00007bff808b3840, D=0x00007e0f841bb3c8) at DeclNodes.inc:256:1
    frame #<!-- -->14: 0x00007fffe4223810 libclang-cpp.so.21.0git`clang::Sema::SubstDecl(clang::Decl*, clang::DeclContext*, clang::MultiLevelTemplateArgumentList const&amp;)::$_0::operator()(this=0x00007bff808b39a0) const at SemaTemplateInstantiateDecl.cpp:4616:27
    frame #<!-- -->15: 0x00007fffe4223715 libclang-cpp.so.21.0git`void llvm::function_ref&lt;void ()&gt;::callback_fn&lt;clang::Sema::SubstDecl(clang::Decl*, clang::DeclContext*, clang::MultiLevelTemplateArgumentList const&amp;)::$_0&gt;(callable=136337303484832) at STLFunctionalExtras.h:46:12
    frame #<!-- -->16: 0x00007fffdb93ae2c libclang-cpp.so.21.0git`llvm::function_ref&lt;void ()&gt;::operator()(this=0x00007bff805c8de0) const at STLFunctionalExtras.h:69:12
    frame #<!-- -->17: 0x00007fffdb93b6a5 libclang-cpp.so.21.0git`clang::runWithSufficientStackSpace(Diag=function_ref&lt;void ()&gt; @ 0x00007ffffffe21b8, Fn=function_ref&lt;void ()&gt; @ 0x00007bff805c8de0) at Stack.h:49:7
    frame #<!-- -->18: 0x00007fffdb93b00c libclang-cpp.so.21.0git`clang::StackExhaustionHandler::runWithSufficientStackSpace(this=0x00007e8f82192460, Loc=(ID = 2147483606), Fn=function_ref&lt;void ()&gt; @ 0x00007ffffffe22b8) at StackExhaustionHandler.cpp:20:3
    frame #<!-- -->19: 0x00007fffe09b87a6 libclang-cpp.so.21.0git`clang::Sema::runWithSufficientStackSpace(this=0x00007e8f82192200, Loc=(ID = 2147483606), Fn=function_ref&lt;void ()&gt; @ 0x00007ffffffe2338) at Sema.cpp:606:16
    frame #<!-- -->20: 0x00007fffe4081b2e libclang-cpp.so.21.0git`clang::Sema::SubstDecl(this=0x00007e8f82192200, D=0x00007e0f841bb3c8, Owner=0x00007e0f841b6d30, TemplateArgs=0x00007bff80a8bb40) at SemaTemplateInstantiateDecl.cpp:4615:3
    frame #<!-- -->21: 0x00007fffe3a68a1d libclang-cpp.so.21.0git`clang::Sema::FinishTemplateArgumentDeduction(this=0x00007e8f82192200, FunctionTemplate=0x00007e0f841bb1e8, Deduced=0x00007bff80bd8220, NumExplicitlySpecified=0, Specialization=0x00007bff80a8b2e0, Info=0x00007bff80a8b0a0, OriginalCallArgs=0x00007bff80bd8400, PartialOverloading=true, PartialOrdering=false, CheckNonDependent=function_ref&lt;bool ()&gt; @ 0x00007bff80a8b820) at SemaTemplateDeduction.cpp:3947:7

The template argument is:

(clang::TemplateArgument) {
   = {
    DeclArg = {
      Kind = Null
      IsDefaulted = false
      QT = 0x0000000000000000
      D = 0x00007fffd22b2140
    }
    Integer = {
      Kind = Null
      IsDefaulted = false
      BitWidth = 32766
      IsUnsigned = false
       = {
        VAL = 0
        pVal = 0x0000000000000000
      }
      Type = 0x00007fffd22b2140
    }
    Value = {
      Kind = Null
      IsDefaulted = false
      Value = nullptr
      Type = 0x00007fffd22b2140
    }
    Args = {
      Kind = Null
      IsDefaulted = false
      NumArgs = 32766
      Args = nullptr
    }
    TemplateArg = {
      Kind = Null
      IsDefaulted = false
      NumExpansions = (Rep = 32766)
      Name = 0x0000000000000000
    }
    TypeOrValue = (Kind = Null, IsDefaulted = false, IsCanonicalExpr = false, V = 0)
  }
}

tbaederr · 2025-05-08T08:05:28Z

I bisected this to 20e9049

CC @ChuanqiXu9

ChuanqiXu9 · 2025-05-08T09:35:09Z

I bisected this to 20e9049

CC @ChuanqiXu9

I suspect it relates to spec_begin and spec_end. The story is, if more specializations are loaded, the iterators may be invalided.

Would you like to verify if it is the case? If yes, may be we can fix the problem by storing all iterators before traversing.

(I am busy with other things and might not be able to do detailed debugging recently, sorry)

tbaederr · 2025-05-08T10:46:37Z

I know little to nothing about this part of clang, but if you can give me some details, I can verify that, yes.

ChuanqiXu9 · 2025-05-08T10:54:09Z

I know little to nothing about this part of clang, but if you can give me some details, I can verify that, yes.

The pattern I suspect is:

for (auto &Iter : template_decl.specializations()) // RedeclarableTemplateDecl::specializations() is the point
{
     ...
}

or

auto Iter = template_decl.spec_begin();
auto E = template_decl.spec_end();
for (; Iter != E; Iter++) {
     ...
}

the pattern is, the core happens at Iter++. In another word, invalided iterator.

ChuanqiXu9 · 2025-05-12T02:03:23Z

See the comment from clangd/clangd#2387 (comment)

HighCommander4 · 2025-05-12T02:05:47Z

(Note the duplicate report has a testcase which is valid code, so adding crash-on-valid.)

llvmbot · 2025-05-12T02:06:26Z

@llvm/issue-subscribers-clang-frontend

Author: Timm Baeder (tbaederr)

For these two files: ```c++ // test.cpp #include "test.h"

void run(int num_total_tasks) {
int cnt{};
int x;

for (int i = 0; i < min(x, num_total_tas - cnt); ++i) {}
}


```c++
// test.h
template&lt;typename T&gt;
T min(T A, T B) { return A &lt; B ? A : B; }

bin/clangd --check=test.cpp --check-completion crashes:

Expected valid TemplateArgument
UNREACHABLE executed at /home/tbaeder/code/llvm-project/clang/lib/Serialization/TemplateArgumentHasher.cpp:68!
Process 3542402 stopped
* thread #<!-- -->1, name = 'clangd', stop reason = signal SIGABRT
    frame #<!-- -->0: 0x00007fff8287ff54 libc.so.6`__pthread_kill_implementation + 276
libc.so.6`__pthread_kill_implementation:
-&gt;  0x7fff8287ff54 &lt;+276&gt;: movl   %eax, %ebx
    0x7fff8287ff56 &lt;+278&gt;: negl   %ebx
    0x7fff8287ff58 &lt;+280&gt;: cmpl   $0xfffff000, %eax ; imm = 0xFFFFF000
    0x7fff8287ff5d &lt;+285&gt;: movl   $0x0, %eax
(lldb) bt
* thread #<!-- -->1, name = 'clangd', stop reason = signal SIGABRT
  * frame #<!-- -->0: 0x00007fff8287ff54 libc.so.6`__pthread_kill_implementation + 276
    frame #<!-- -->1: 0x00007fff82826f9e libc.so.6`raise + 30
    frame #<!-- -->2: 0x00007fff8280e942 libc.so.6`abort + 223
    frame #<!-- -->3: 0x00007fffa25151d5 libLLVM.so.21.0git`llvm::llvm_unreachable_internal(msg="Expected valid TemplateArgument", file="/home/tbaeder/code/llvm-project/clang/lib/Serialization/TemplateArgumentHasher.cpp", line=68) at ErrorHandling.cpp:233:3
    frame #<!-- -->4: 0x00007fffe8b473c9 libclang-cpp.so.21.0git`(anonymous namespace)::TemplateArgumentHasher::AddTemplateArgument(this=0x00007bff808b3e40, TA=TemplateArgument @ 0x00007bff8071a720) at TemplateArgumentHasher.cpp:68:5
    frame #<!-- -->5: 0x00007fffe8b46f3c libclang-cpp.so.21.0git`clang::serialization::StableHashForTemplateArguments(Args=ArrayRef&lt;clang::TemplateArgument&gt; @ 0x00007bff808b3e20) at TemplateArgumentHasher.cpp:409:12
    frame #<!-- -->6: 0x00007fffe83b71f0 libclang-cpp.so.21.0git`clang::ASTReader::LoadExternalSpecializationsImpl(this=0x00007e8f8218d200, SpecLookups=0x00007e8f8218e188, D=0x00007e0f841bb1e8, TemplateArgs=ArrayRef&lt;clang::TemplateArgument&gt; @ 0x00007ffffffe0d30) at ASTReader.cpp:8388:20
    frame #<!-- -->7: 0x00007fffe83b77b3 libclang-cpp.so.21.0git`clang::ASTReader::LoadExternalSpecializations(this=0x00007e8f8218d200, D=0x00007e0f841bb1e8, TemplateArgs=ArrayRef&lt;clang::TemplateArgument&gt; @ 0x00007ffffffe0e00) at ASTReader.cpp:8412:7
    frame #<!-- -->8: 0x00007fffdd9eae82 libclang-cpp.so.21.0git`clang::RedeclarableTemplateDecl::loadLazySpecializationsImpl(this=0x00007e0f841bb1e8, Args=ArrayRef&lt;clang::TemplateArgument&gt; @ 0x00007ffffffe0ea8, TPL=0x0000000000000000) const at DeclTemplate.cpp:377:26
    frame #<!-- -->9: 0x00007fffdda040e8 libclang-cpp.so.21.0git`clang::RedeclarableTemplateDecl::SpecEntryTraits&lt;clang::FunctionTemplateSpecializationInfo&gt;::DeclType* clang::RedeclarableTemplateDecl::findSpecializationImpl&lt;clang::FunctionTemplateSpecializationInfo, llvm::ArrayRef&lt;clang::TemplateArgument&gt;&amp;&gt;(this=0x00007e0f841bb1e8, Specs=0x00007e0f841bb250, InsertPos=0x00007bff80bd9040, ProfileArgs=0x00007bff805c8f20) at DeclTemplate.cpp:405:8
    frame #<!-- -->10: 0x00007fffdd9eba3d libclang-cpp.so.21.0git`clang::FunctionTemplateDecl::findSpecialization(this=0x00007e0f841bb1e8, Args=ArrayRef&lt;clang::TemplateArgument&gt; @ 0x00007bff805c8f20, InsertPos=0x00007bff80bd9040) at DeclTemplate.cpp:487:10
    frame #<!-- -->11: 0x00007fffe405c00c libclang-cpp.so.21.0git`clang::TemplateDeclInstantiator::VisitFunctionDecl(this=0x00007bff808b3840, D=0x00007e0f841bb3c8, TemplateParams=0x0000000000000000, FunctionRewriteKind=None) at SemaTemplateInstantiateDecl.cpp:2623:27
    frame #<!-- -->12: 0x00007fffe407cf13 libclang-cpp.so.21.0git`clang::TemplateDeclInstantiator::VisitFunctionDecl(this=0x00007bff808b3840, D=0x00007e0f841bb3c8) at SemaTemplateInstantiateDecl.cpp:4343:10
    frame #<!-- -->13: 0x00007fffe3fe94b0 libclang-cpp.so.21.0git`clang::declvisitor::Base&lt;std::add_pointer, clang::TemplateDeclInstantiator, clang::Decl*&gt;::Visit(this=0x00007bff808b3840, D=0x00007e0f841bb3c8) at DeclNodes.inc:256:1
    frame #<!-- -->14: 0x00007fffe4223810 libclang-cpp.so.21.0git`clang::Sema::SubstDecl(clang::Decl*, clang::DeclContext*, clang::MultiLevelTemplateArgumentList const&amp;)::$_0::operator()(this=0x00007bff808b39a0) const at SemaTemplateInstantiateDecl.cpp:4616:27
    frame #<!-- -->15: 0x00007fffe4223715 libclang-cpp.so.21.0git`void llvm::function_ref&lt;void ()&gt;::callback_fn&lt;clang::Sema::SubstDecl(clang::Decl*, clang::DeclContext*, clang::MultiLevelTemplateArgumentList const&amp;)::$_0&gt;(callable=136337303484832) at STLFunctionalExtras.h:46:12
    frame #<!-- -->16: 0x00007fffdb93ae2c libclang-cpp.so.21.0git`llvm::function_ref&lt;void ()&gt;::operator()(this=0x00007bff805c8de0) const at STLFunctionalExtras.h:69:12
    frame #<!-- -->17: 0x00007fffdb93b6a5 libclang-cpp.so.21.0git`clang::runWithSufficientStackSpace(Diag=function_ref&lt;void ()&gt; @ 0x00007ffffffe21b8, Fn=function_ref&lt;void ()&gt; @ 0x00007bff805c8de0) at Stack.h:49:7
    frame #<!-- -->18: 0x00007fffdb93b00c libclang-cpp.so.21.0git`clang::StackExhaustionHandler::runWithSufficientStackSpace(this=0x00007e8f82192460, Loc=(ID = 2147483606), Fn=function_ref&lt;void ()&gt; @ 0x00007ffffffe22b8) at StackExhaustionHandler.cpp:20:3
    frame #<!-- -->19: 0x00007fffe09b87a6 libclang-cpp.so.21.0git`clang::Sema::runWithSufficientStackSpace(this=0x00007e8f82192200, Loc=(ID = 2147483606), Fn=function_ref&lt;void ()&gt; @ 0x00007ffffffe2338) at Sema.cpp:606:16
    frame #<!-- -->20: 0x00007fffe4081b2e libclang-cpp.so.21.0git`clang::Sema::SubstDecl(this=0x00007e8f82192200, D=0x00007e0f841bb3c8, Owner=0x00007e0f841b6d30, TemplateArgs=0x00007bff80a8bb40) at SemaTemplateInstantiateDecl.cpp:4615:3
    frame #<!-- -->21: 0x00007fffe3a68a1d libclang-cpp.so.21.0git`clang::Sema::FinishTemplateArgumentDeduction(this=0x00007e8f82192200, FunctionTemplate=0x00007e0f841bb1e8, Deduced=0x00007bff80bd8220, NumExplicitlySpecified=0, Specialization=0x00007bff80a8b2e0, Info=0x00007bff80a8b0a0, OriginalCallArgs=0x00007bff80bd8400, PartialOverloading=true, PartialOrdering=false, CheckNonDependent=function_ref&lt;bool ()&gt; @ 0x00007bff80a8b820) at SemaTemplateDeduction.cpp:3947:7

The template argument is:

(clang::TemplateArgument) {
   = {
    DeclArg = {
      Kind = Null
      IsDefaulted = false
      QT = 0x0000000000000000
      D = 0x00007fffd22b2140
    }
    Integer = {
      Kind = Null
      IsDefaulted = false
      BitWidth = 32766
      IsUnsigned = false
       = {
        VAL = 0
        pVal = 0x0000000000000000
      }
      Type = 0x00007fffd22b2140
    }
    Value = {
      Kind = Null
      IsDefaulted = false
      Value = nullptr
      Type = 0x00007fffd22b2140
    }
    Args = {
      Kind = Null
      IsDefaulted = false
      NumArgs = 32766
      Args = nullptr
    }
    TemplateArg = {
      Kind = Null
      IsDefaulted = false
      NumExpansions = (Rep = 32766)
      Name = 0x0000000000000000
    }
    TypeOrValue = (Kind = Null, IsDefaulted = false, IsCanonicalExpr = false, V = 0)
  }
}

HighCommander4 · 2025-05-12T03:08:06Z

I sent out #139489 to clean up the "arguments std::forwarded multiple times" situation discussed in the comment linked above, but indeed it does not resolve the crash.

tbaederr · 2025-05-12T15:17:38Z

I fixed it!

diff --git i/clang/lib/Sema/SemaTemplateDeduction.cpp w/clang/lib/Sema/SemaTemplateDeduction.cpp
index 5dc06ebc2a23..032c5b314fd1 100644
--- i/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ w/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -3045,6 +3045,7 @@ static TemplateDeductionResult ConvertDeducedTemplateArguments(
     // consider template parameters that were deduced, disregarding any default
     // arguments.
     if (IsIncomplete) {
+      Template->dump();
       *IsIncomplete = true;
       CTAI.SugaredConverted.push_back({});
       CTAI.CanonicalConverted.push_back({});

(wtf?)

tbaederr · 2025-05-12T15:42:19Z

Removing that entire if block also fixes it. CC @mizvekov for some more pointers.

ChuanqiXu9 · 2025-05-13T06:07:19Z

I fixed it!

diff --git i/clang/lib/Sema/SemaTemplateDeduction.cpp w/clang/lib/Sema/SemaTemplateDeduction.cpp
index 5dc06ebc2a23..032c5b314fd1 100644
--- i/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ w/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -3045,6 +3045,7 @@ static TemplateDeductionResult ConvertDeducedTemplateArguments(
// consider template parameters that were deduced, disregarding any default
// arguments.
if (IsIncomplete) {
 Template->dump();
 *IsIncomplete = true;
 CTAI.SugaredConverted.push_back({});
 CTAI.CanonicalConverted.push_back({});
(wtf?)

dump will trigger the compiler to load a lot of things. I guess this is the reason.

tbaederr added clangd crash-on-invalid labels May 8, 2025

ChuanqiXu9 mentioned this issue May 12, 2025

[clang][20.x regression] Crash during code completion when using PCH #139486

Closed

HighCommander4 added the crash-on-valid label May 12, 2025

HighCommander4 added the clang:frontend Language frontend issues, e.g. anything involving "Sema" label May 12, 2025

ChuanqiXu9 mentioned this issue May 12, 2025

since clang 20.x, clangd crashes constantly clangd/clangd#2387

Closed

EugeneZelenko marked this as a duplicate of #139486 May 12, 2025

zyn0217 mentioned this issue May 12, 2025

clangd Crashes while editing std::find arguments. #139366

Open

HighCommander4 mentioned this issue May 12, 2025

[clang][AST] Pass ProfileArguments by value in findSpecialization{Impl,Locally} #139489

Merged

HighCommander4 added the regression:20 Regression in 20 release label May 12, 2025

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[clangd] "Expected valid TemplateArgument" for `std::min`-like template #139019

[clangd] "Expected valid TemplateArgument" for `std::min`-like template #139019

tbaederr commented May 8, 2025

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tbaederr commented May 8, 2025

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tbaederr commented May 8, 2025

ChuanqiXu9 commented May 8, 2025

ChuanqiXu9 commented May 12, 2025

HighCommander4 commented May 12, 2025

llvmbot commented May 12, 2025

HighCommander4 commented May 12, 2025

tbaederr commented May 12, 2025

tbaederr commented May 12, 2025

ChuanqiXu9 commented May 13, 2025

[clangd] "Expected valid TemplateArgument" for std::min-like template #139019

[clangd] "Expected valid TemplateArgument" for std::min-like template #139019

Comments

tbaederr commented May 8, 2025

llvmbot commented May 8, 2025

tbaederr commented May 8, 2025

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tbaederr commented May 8, 2025

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ChuanqiXu9 commented May 12, 2025

HighCommander4 commented May 12, 2025

llvmbot commented May 12, 2025

HighCommander4 commented May 12, 2025

tbaederr commented May 12, 2025

tbaederr commented May 12, 2025

ChuanqiXu9 commented May 13, 2025

[clangd] "Expected valid TemplateArgument" for `std::min`-like template #139019

[clangd] "Expected valid TemplateArgument" for `std::min`-like template #139019