Clang 15 |ReleaseNotesTitle|¶
Written by the LLVM Team
Introduction¶
This document contains the release notes for the Clang C/C++/Objective-C frontend, part of the LLVM Compiler Infrastructure, release 15. Here we describe the status of Clang in some detail, including major improvements from the previous release and new feature work. For the general LLVM release notes, see the LLVM documentation. For the libc++ release notes, see this page. All LLVM releases may be downloaded from the LLVM releases web site.
For more information about Clang or LLVM, including information about the latest release, please see the Clang Web Site or the LLVM Web Site.
Potentially Breaking Changes¶
The Objective-C ARC migrator (ARCMigrate) has been removed.
C/C++ Language Potentially Breaking Changes¶
C++ Specific Potentially Breaking Changes¶
The type trait builtin
__is_referenceable
has been removed, since it has very few users and all the type traits that could benefit from it in the standard library already have their own bespoke builtins.
ABI Changes in This Version¶
Return larger CXX records in memory instead of using AVX registers. Code compiled with older clang will be incompatible with newer version of the clang unless -fclang-abi-compat=20 is provided. (#120670)
AST Dumping Potentially Breaking Changes¶
Added support for dumping template arguments of structural value kinds.
Clang Frontend Potentially Breaking Changes¶
Clang Python Bindings Potentially Breaking Changes¶
What’s New in Clang 15?¶
C++ Language Changes¶
C++2c Feature Support¶
Implemented P1061R10 Structured Bindings can introduce a Pack.
C++23 Feature Support¶
C++20 Feature Support¶
C++17 Feature Support¶
Resolutions to C++ Defect Reports¶
The flag -frelaxed-template-template-args and its negation have been removed, having been deprecated since the previous two releases. The improvements to template template parameter matching implemented in the previous release, as described in P3310 and P3579, made this flag unnecessary.
C Language Changes¶
Clang now allows an
inline
specifier on a typedef declaration of a function type in Microsoft compatibility mode. #124869Clang now allows
restrict
qualifier for array types with pointer elements (#92847).
C2y Feature Support¶
C23 Feature Support¶
Non-comprehensive list of changes in this release¶
New Compiler Flags¶
Deprecated Compiler Flags¶
Modified Compiler Flags¶
Removed Compiler Flags¶
Attribute Changes in Clang¶
The
no_sanitize
attribute now accepts bothgnu
andclang
names.Clang now diagnoses use of declaration attributes on void parameters. (#108819)
Clang now allows
__attribute__((model("small")))
and__attribute__((model("large")))
on non-TLS globals in x86-64 compilations. This forces the global to be considered small or large in regards to the x86-64 code model, regardless of the code model specified for the compilation.
Improvements to Clang’s diagnostics¶
Improve the diagnostics for deleted default constructor errors for C++ class initializer lists that don’t explicitly list a class member and thus attempt to implicitly default construct that member.
The
-Wunique-object-duplication
warning has been added to warn about objects which are supposed to only exist once per program, but may get duplicated when built into a shared library.Fixed a bug where Clang’s Analysis did not correctly model the destructor behavior of
union
members (#119415).A statement attribute applied to a
case
label no longer suppresses ‘bypassing variable initialization’ diagnostics (#84072).The
-Wunsafe-buffer-usage
warning has been updated to warn about unsafe libc function calls. Those new warnings are emitted under the subgroup-Wunsafe-buffer-usage-in-libc-call
.Diagnostics on chained comparisons (
a < b < c
) are now an error by default. This can be disabled with-Wno-error=parentheses
.
Improvements to Clang’s time-trace¶
Improvements to Coverage Mapping¶
Bug Fixes in This Version¶
Clang now outputs correct values when #embed data contains bytes with negative signed char values (#102798).
Bug Fixes to Compiler Builtins¶
The behvaiour of
__add_pointer
and__remove_pointer
for Objective-C++’sid
and interfaces has been fixed.
Bug Fixes to Attribute Support¶
Fixed crash when a parameter to the
clang::annotate
attribute evaluates tovoid
. See #119125
Bug Fixes to C++ Support¶
Clang is now better at keeping track of friend function template instance contexts. (#55509)
Clang now prints the correct instantiation context for diagnostics suppressed by template argument deduction.
The initialization kind of elements of structured bindings direct-list-initialized from an array is corrected to direct-initialization.
Clang no longer crashes when a coroutine is declared
[[noreturn]]
. (#127327)
Bug Fixes to AST Handling¶
Fixed type checking when a statement expression ends in an l-value of atomic type. (#106576)
Miscellaneous Bug Fixes¶
HTML tags in comments that span multiple lines are now parsed correctly by Clang’s comment parser. (#120843)
Miscellaneous Clang Crashes Fixed¶
OpenACC Specific Changes¶
Target Specific Changes¶
AMDGPU Support¶
NVPTX Support¶
Hexagon Support¶
The default compilation target has been changed from V60 to V68.
X86 Support¶
Disable
-m[no-]avx10.1
and switch-m[no-]avx10.2
to alias of 512 bit options.Change
-mno-avx10.1-512
to alias of-mno-avx10.1-256
to disable both 256 and 512 bit instructions.
Arm and AArch64 Support¶
Android Support¶
Windows Support¶
LoongArch Support¶
RISC-V Support¶
Add support for -mtune=generic-ooo (a generic out-of-order model).
CUDA/HIP Language Changes¶
CUDA Support¶
AIX Support¶
NetBSD Support¶
WebAssembly Support¶
AVR Support¶
DWARF Support in Clang¶
Floating Point Support in Clang¶
Fixed Point Support in Clang¶
AST Matchers¶
clang-format¶
Adds
BreakBeforeTemplateCloser
option.Adds
BinPackLongBracedList
option to override bin packing options in long (20 item or more) braced list initializer lists.
libclang¶
Fixed a buffer overflow in
CXString
implementation. The fix may result in increased memory allocation.
Code Completion¶
Static Analyzer¶
New features¶
A new flag - -static-libclosure was introduced to support statically linking the runtime for the Blocks extension on Windows. This flag currently only changes the code generation, and even then, only on Windows. This does not impact the linker behaviour like the other -static-* flags.
Crash and bug fixes¶
Improvements¶
Moved checkers¶
After lots of improvements, the checker
alpha.security.ArrayBoundV2
is renamed tosecurity.ArrayBound
. As this checker is stable now, the old checkeralpha.security.ArrayBound
(which was searching for the same kind of bugs with an different, simpler and less accurate algorithm) is removed.
Sanitizers¶
Python Binding Changes¶
OpenMP Support¶
Added support ‘no_openmp_constructs’ assumption clause.
Added support for ‘omp stripe’ directive.
Improvements¶
Additional Information¶
A wide variety of additional information is available on the Clang web
page. The web page contains versions of the
API documentation which are up-to-date with the Git version of
the source code. You can access versions of these documents specific to
this release by going into the “clang/docs/
” directory in the Clang
tree.
If you have any questions or comments about Clang, please feel free to contact us on the Discourse forums (Clang Frontend category).