[all-commits] [llvm/llvm-project] 281d17: [clang] Diagnose functions with too many parameter...

[Vlad Serebrennikov via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 281d17840c35a1d80303bb6170c253fe2411f95f
      https://github.com/llvm/llvm-project/commit/281d17840c35a1d80303bb6170c253fe2411f95f
  Author: Vlad Serebrennikov <serebrennikov.vladislav at gmail.com>
  Date:   2024-08-21 (Wed, 21 Aug 2024)

  Changed paths:
    M clang/docs/ReleaseNotes.rst
    M clang/include/clang/AST/Type.h
    M clang/include/clang/Basic/DiagnosticParseKinds.td
    M clang/lib/Parse/ParseDecl.cpp
    A clang/test/Parser/function-parameter-limit.cpp

  Log Message:
  -----------
  [clang] Diagnose functions with too many parameters (#104833)

This patch adds a parser check when a function declaration or function
type declaration (in a function pointer declaration, for example) has
too many parameters for `FunctionTypeBits::NumParams` to hold. At the
moment of writing it's a 16-bit-wide bit-field, limiting the number of
parameters at 65536.

The check is added in the parser loop that goes over comma-separated
list of function parameters. This is not the solution Aaron suggested in
https://github.com/llvm/llvm-project/issues/35741#issuecomment-1638086571,
because it was found out that it's quite hard to recover from this
particular error in `GetFullTypeForDeclarator()`. Multiple options were
tried, but all of them led to crashes down the line.

I used LLVM Compile Time Tracker to ensure this does not introduce a
performance regression. I believe changes are in the noise:
https://llvm-compile-time-tracker.com/compare.php?from=de5ea2d122c31e1551654ff506c33df299f351b8&to=424818620766cedb2770e076ee359afeb0cc14ec&stat=instructions:u

Fixes #35741



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