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[clang] Serialization: support hashing null template arguments #141890

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merged 1 commit into from
May 29, 2025
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[clang] Serialization: support hashing null template arguments #141890

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1 change: 1 addition & 0 deletions clang/docs/ReleaseNotes.rst
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Expand Up @@ -821,6 +821,7 @@ Miscellaneous Clang Crashes Fixed
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

- Fixed crash when ``-print-stats`` is enabled in compiling IR files. (#GH131608)
- Fix code completion crash involving PCH serialzied templates. (#GH139019)

OpenACC Specific Changes
------------------------
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4 changes: 3 additions & 1 deletion clang/lib/Serialization/TemplateArgumentHasher.cpp
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Expand Up @@ -65,7 +65,9 @@ void TemplateArgumentHasher::AddTemplateArgument(TemplateArgument TA) {

switch (Kind) {
case TemplateArgument::Null:
llvm_unreachable("Expected valid TemplateArgument");
// These can occur in incomplete substitutions performed with code
// completion (see PartialOverloading).
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@shafik shafik May 30, 2025

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see PartialOverloading where? Is there a specific method or API doc we should look at?

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@mizvekov mizvekov May 30, 2025

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It's the term of art within clang, and the name of the flag as used in source code.
A search on doxygen for this term should lead to:

  /// AddOverloadCandidate - Adds the given function to the set of
  /// candidate functions, using the given function call arguments.  If
  /// @p SuppressUserConversions, then don't allow user-defined
  /// conversions via constructors or conversion operators.
  ///
  /// \param PartialOverloading true if we are performing "partial" overloading
  /// based on an incomplete set of function arguments. This feature is used by
  /// code completion.

This term can also easily be greped for, and there are no irrelevant results.
But this is mostly undocumented.

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@shafik shafik May 30, 2025

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So I am using Visual Studio code and did a naive search for PartialOverloading and it was definitely not obvious where I specifically should look for this term. I did spend some time trying to dig around.

I think my point is that the comment is not super helpful unless you already have some understanding. So it requires a bit more elaboration so that random folks who come upon can get it.

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@mizvekov mizvekov May 30, 2025

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I think this name is the best stable reference to this functionality.
And I don't think mentioning file names is a good idea, and there is no documentation to point to.

Is there any specific thing this comment should say so you think this would be easier to find?

break;
case TemplateArgument::Type:
AddQualType(TA.getAsType());
break;
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26 changes: 26 additions & 0 deletions clang/test/CodeCompletion/GH139019.cpp
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@@ -0,0 +1,26 @@
// RUN: rm -rf %t
// RUN: mkdir %t
// RUN: split-file %s %t
//
// RUN: %clang_cc1 -std=c++20 %t/test.hpp -emit-pch -o %t/1.pch
// RUN: %clang_cc1 -std=c++20 %t/test.cpp -include-pch %t/1.pch -code-completion-at=%t/test.cpp:7:17

//--- test.hpp
#pragma once
class provider_t
{
public:
template<class T>
void emit(T *data)
{}
};

//--- test.cpp
#include "test.hpp"

void test()
{
provider_t *focus;
void *data;
focus->emit(&data);
}
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