[all-commits] [llvm/llvm-project] c71011: [clang] Implement __attribute__((format_matches)) ...

[apple-fcloutier via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: c7101188fb3f17176e9152b1d733da6d7199d317
      https://github.com/llvm/llvm-project/commit/c7101188fb3f17176e9152b1d733da6d7199d317
  Author: apple-fcloutier <75502309+apple-fcloutier at users.noreply.github.com>
  Date:   2025-02-24 (Mon, 24 Feb 2025)

  Changed paths:
    M clang/docs/ReleaseNotes.rst
    M clang/include/clang/AST/FormatString.h
    M clang/include/clang/Basic/Attr.td
    M clang/include/clang/Basic/AttrDocs.td
    M clang/include/clang/Basic/DiagnosticSemaKinds.td
    M clang/include/clang/Sema/Sema.h
    M clang/lib/AST/AttrImpl.cpp
    M clang/lib/AST/FormatString.cpp
    M clang/lib/Sema/SemaChecking.cpp
    M clang/lib/Sema/SemaDecl.cpp
    M clang/lib/Sema/SemaDeclAttr.cpp
    M clang/lib/Sema/SemaObjC.cpp
    A clang/test/Sema/format-string-matches.c
    M clang/test/Sema/format-strings.c

  Log Message:
  -----------
  [clang] Implement __attribute__((format_matches)) (#116708)

This implements ``__attribute__((format_matches))``, as described in the
RFC:
https://discourse.llvm.org/t/rfc-format-attribute-attribute-format-like/83076

The ``format`` attribute only allows the compiler to check that a format
string matches its arguments. If the format string is passed
independently of its arguments, there is no way to have the compiler
check it. ``format_matches(flavor, fmtidx, example)`` allows the
compiler to check format strings against the ``example`` format string
instead of against format arguments. See the changes to AttrDocs.td in
this diff for more information.

Implementation-wise, this change subclasses CheckPrintfHandler and
CheckScanfHandler to allow them to collect specifiers into arrays, and
implements comparing that two specifiers are equivalent.
`checkFormatStringExpr` gets a new `ReferenceFormatString` argument that
is piped down when calling a function with the `format_matches`
attribute (and is `nullptr` otherwise); this is the string that the
actual format string is compared against.

Although this change does not enable -Wformat-nonliteral by default,
IMO, all the pieces are now in place such that it could be.



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