1======================================== 2Clang 13.0.0 Release Notes 3======================================== 4 5.. contents:: 6 :local: 7 :depth: 2 8 9Written by the `LLVM Team <https://llvm.org/>`_ 10 11Introduction 12============ 13 14This document contains the release notes for the Clang C/C++/Objective-C 15frontend, part of the LLVM Compiler Infrastructure, release 13.0.0. Here we 16describe the status of Clang in some detail, including major 17improvements from the previous release and new feature work. For the 18general LLVM release notes, see `the LLVM 19documentation <https://llvm.org/docs/ReleaseNotes.html>`_. All LLVM 20releases may be downloaded from the `LLVM releases web 21site <https://llvm.org/releases/>`_. 22 23For more information about Clang or LLVM, including information about the 24latest release, please see the `Clang Web Site <https://clang.llvm.org>`_ or the 25`LLVM Web Site <https://llvm.org>`_. 26 27Note that if you are reading this file from a Git checkout or the 28main Clang web page, this document applies to the *next* release, not 29the current one. To see the release notes for a specific release, please 30see the `releases page <https://llvm.org/releases/>`_. 31 32What's New in Clang 13.0.0? 33=========================== 34 35Some of the major new features and improvements to Clang are listed 36here. Generic improvements to Clang as a whole or to its underlying 37infrastructure are described first, followed by language-specific 38sections with improvements to Clang's support for those languages. 39 40Major New Features 41------------------ 42 43- Guaranteed tail calls are now supported with statement attributes 44 ``[[clang::musttail]]`` in C++ and ``__attribute__((musttail))`` in C. The 45 attribute is applied to a return statement (not a function declaration), 46 and an error is emitted if a tail call cannot be guaranteed, for example if 47 the function signatures of caller and callee are not compatible. Guaranteed 48 tail calls enable a class of algorithms that would otherwise use an 49 arbitrary amount of stack space. 50 51Improvements to Clang's diagnostics 52^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 53 54- ... 55 56Non-comprehensive list of changes in this release 57------------------------------------------------- 58 59- The default value of _MSC_VER was raised from 1911 to 1914. MSVC 19.14 has the 60 support to overaligned objects on x86_32 which is required for some LLVM 61 passes. 62 63New Compiler Flags 64------------------ 65 66- ``-Wreserved-identifier`` emits warning when user code uses reserved 67 identifiers. 68 69- ``Wunused-but-set-parameter`` and ``-Wunused-but-set-variable`` emit warnings 70 when a parameter or a variable is set but not used. 71 72- ``-fstack-usage`` generates an extra .su file per input source file. The .su 73 file contains frame size information for each function defined in the source 74 file. 75 76- ``-Wnull-pointer-subtraction`` emits warning when user code may have 77 undefined behaviour due to subtraction involving a null pointer. 78 79Deprecated Compiler Flags 80------------------------- 81 82- ... 83 84Modified Compiler Flags 85----------------------- 86 87- -Wshadow now also checks for shadowed structured bindings 88- ``-B <prefix>`` (when ``<prefix>`` is a directory) was overloaded to additionally 89 detect GCC installations under ``<prefix>`` (``lib{,32,64}/gcc{,-cross}/$triple``). 90 This behavior was incompatible with GCC, caused interop issues with 91 ``--gcc-toolchain``, and was thus dropped. Specify ``--gcc-toolchain=<dir>`` 92 instead. ``-B``'s other GCC-compatible semantics are preserved: 93 ``$prefix/$triple-$file`` and ``$prefix$file`` are searched for executables, 94 libraries, includes, and data files used by the compiler. 95- ``-Wextra`` now also implies ``-Wnull-pointer-subtraction.`` 96 97Removed Compiler Flags 98------------------------- 99 100- The clang-cl ``/fallback`` flag, which made clang-cl invoke Microsoft Visual 101 C++ on files it couldn't compile itself, has been removed. 102 103- ``-Wreturn-std-move-in-c++11``, which checked whether an entity is affected by 104 `CWG1579 <https://wg21.link/CWG1579>`_ to become implicitly movable, has been 105 removed. 106 107New Pragmas in Clang 108-------------------- 109 110- ... 111 112Attribute Changes in Clang 113-------------------------- 114 115- ... 116 117- Added support for C++11-style ``[[]]`` attributes on using-declarations, as a 118 clang extension. 119 120Windows Support 121--------------- 122 123- Fixed reading ``long double`` arguments with ``va_arg`` on x86_64 MinGW 124 targets. 125 126C Language Changes in Clang 127--------------------------- 128 129- ... 130 131C++ Language Changes in Clang 132----------------------------- 133 134- The oldest supported GNU libstdc++ is now 4.8.3 (released 2014-05-22). 135 Clang workarounds for bugs in earlier versions have been removed. 136 137- ... 138 139C++20 Feature Support 140^^^^^^^^^^^^^^^^^^^^^ 141... 142 143C++2b Feature Support 144^^^^^^^^^^^^^^^^^^^^^ 145... 146 147Objective-C Language Changes in Clang 148------------------------------------- 149 150OpenCL Kernel Language Changes in Clang 151--------------------------------------- 152 153 154Command-line interface changes: 155 156- All builtin types, macros and function declarations are now added by default 157 without any command-line flags. A flag is provided ``-cl-no-stdinc`` to 158 suppress the default declarations non-native to the compiler. 159 160- Clang now compiles using OpenCL C version 1.2 by default if no version is 161 specified explicitly from the command line. 162 163- Clang now supports ``.clcpp`` file extension for sources written in 164 C++ for OpenCL. 165 166- Clang now accepts ``-cl-std=clc++1.0`` that sets C++ for OpenCL to 167 the version 1.0 explicitly. 168 169Misc common changes: 170 171- Added ``NULL`` definition in internal headers for standards prior to the 172 version 2.0. 173 174- Simplified use of pragma in extensions for ``double``, images, atomics, 175 subgroups, Arm dot product extension. There are less cases where extension 176 pragma is now required by clang to compile kernel sources. 177 178- Added missing ``as_size``/``as_ptrdiff``/``as_intptr``/``as_uintptr_t`` 179 operators to internal headers. 180 181- Added new builtin function for ndrange, ``cl_khr_subgroup_extended_types``, 182 ``cl_khr_subgroup_non_uniform_vote``, ``cl_khr_subgroup_ballot``, 183 ``cl_khr_subgroup_non_uniform_arithmetic``, ``cl_khr_subgroup_shuffle``, 184 ``cl_khr_subgroup_shuffle_relative``, ``cl_khr_subgroup_clustered_reduce`` 185 into the default Tablegen-based header. 186 187- Added online documentation for Tablegen-based header, OpenCL 3.0 support, 188 new clang extensions. 189 190- Fixed OpenCL C language version and SPIR address space reporting in DWARF. 191 192New extensions: 193 194- ``cl_khr_integer_dot_product`` for dedicated support of dot product. 195 196- ``cl_khr_extended_bit_ops`` for dedicated support of extra binary operations. 197 198- ``__cl_clang_bitfields`` for use of bit-fields in the kernel code. 199 200- ``__cl_clang_non_portable_kernel_param_types`` for relaxing some restrictions 201 to types of kernel parameters. 202 203OpenCL C 3.0 related changes: 204 205- Added parsing support for the optionality of generic address space, images 206 (including 3d writes and ``read_write`` access qualifier), pipes, program 207 scope variables, double-precision floating-point support. 208 209- Added optionality support for builtin functions (in ``opencl-c.h`` header) 210 for generic address space, C11 atomics. 211 212- Added ``memory_scope_all_devices`` enum for the atomics in internal headers. 213 214- Enabled use of ``.rgba`` vector components. 215 216C++ for OpenCL related changes: 217 218- Added ``__remove_address_space`` metaprogramming utility in internal headers 219 to allow removing address spaces from types. 220 221- Improved overloads resolution logic for constructors wrt address spaces. 222 223- Improved diagnostics of OpenCL specific types and address space qualified 224 types in ``reinterpret_cast`` and template functions. 225 226- Fixed ``NULL`` macro in internal headers to be compatible with C++. 227 228- Fixed use of ``half`` type. 229 230ABI Changes in Clang 231-------------------- 232 233OpenMP Support in Clang 234----------------------- 235 236- Support for loop transformation directives from OpenMP 5.1 have been added. 237 ``#pragma omp unroll`` is a standardized alternative to ``#pragma unroll`` 238 (or ``#pragma clang loop unroll(enable)``) but also allows composition with 239 other OpenMP loop associated constructs as in 240 241 .. code-block:: c 242 243 #pragma omp parallel for 244 #pragma omp unroll partial(4) 245 for (int i = 0; i < n; ++i) 246 247 ``#pragma omp tile`` applies tiling to a perfect loop nest using a 248 user-defined tile size. 249 250 .. code-block:: c 251 252 #pragma omp tile sizes(8,8) 253 for (int i = 0; i < m; ++i) 254 for (int j = 0; j < n; ++j) 255 256- ... 257 258CUDA Support in Clang 259--------------------- 260 261- ... 262 263X86 Support in Clang 264-------------------- 265 266- ... 267 268Internal API Changes 269-------------------- 270 271These are major API changes that have happened since the 12.0.0 release of 272Clang. If upgrading an external codebase that uses Clang as a library, 273this section should help get you past the largest hurdles of upgrading. 274 275- ... 276 277Build System Changes 278-------------------- 279 280These are major changes to the build system that have happened since the 12.0.0 281release of Clang. Users of the build system should adjust accordingly. 282 283- The option ``LIBCLANG_INCLUDE_CLANG_TOOLS_EXTRA`` no longer exists. There were 284 two releases with that flag forced off, and no uses were added that forced it 285 on. The recommended replacement is clangd. 286 287- ... 288 289AST Matchers 290------------ 291 292- ... 293 294clang-format 295------------ 296 297- Option ``SpacesInLineCommentPrefix`` has been added to control the 298 number of spaces in a line comments prefix. 299 300- Option ``SortIncludes`` has been updated from a ``bool`` to an 301 ``enum`` with backwards compatibility. In addition to the previous 302 ``true``/``false`` states (now ``CaseSensitive``/``Never``), a third 303 state has been added (``CaseInsensitive``) which causes an alphabetical sort 304 with case used as a tie-breaker. 305 306 .. code-block:: c++ 307 308 // Never (previously false) 309 #include "B/A.h" 310 #include "A/B.h" 311 #include "a/b.h" 312 #include "A/b.h" 313 #include "B/a.h" 314 315 // CaseSensitive (previously true) 316 #include "A/B.h" 317 #include "A/b.h" 318 #include "B/A.h" 319 #include "B/a.h" 320 #include "a/b.h" 321 322 // CaseInsensitive 323 #include "A/B.h" 324 #include "A/b.h" 325 #include "a/b.h" 326 #include "B/A.h" 327 #include "B/a.h" 328 329- ``BasedOnStyle: InheritParentConfig`` allows to use the ``.clang-format`` of 330 the parent directories to overwrite only parts of it. 331 332- Option ``IndentAccessModifiers`` has been added to be able to give access 333 modifiers their own indentation level inside records. 334 335- Option ``PPIndentWidth`` has been added to be able to configure pre-processor 336 indentation independent from regular code. 337 338- Option ``ShortNamespaceLines`` has been added to give better control 339 over ``FixNamespaceComments`` when determining a namespace length. 340 341- Support for Whitesmiths has been improved, with fixes for ``namespace`` blocks 342 and ``case`` blocks and labels. 343 344- Option ``EmptyLineAfterAccessModifier`` has been added to remove, force or keep 345 new lines after access modifiers. 346 347- Checks for newlines in option ``EmptyLineBeforeAccessModifier`` are now based 348 on the formatted new lines and not on the new lines in the file. (Fixes 349 https://llvm.org/PR41870.) 350 351- Option ``SpacesInAngles`` has been improved, it now accepts ``Leave`` value 352 that allows to keep spaces where they are already present. 353 354- Option ``AllowShortIfStatementsOnASingleLine`` has been improved, it now 355 accepts ``AllIfsAndElse`` value that allows to put "else if" and "else" short 356 statements on a single line. (Fixes https://llvm.org/PR50019.) 357 358- Option ``BreakInheritanceList`` gets a new style, ``AfterComma``. It breaks 359 only after the commas that separate the base-specifiers. 360 361- Option ``LambdaBodyIndentation`` has been added to control how the body of a 362 lambda is indented. The default ``Signature`` value indents the body one level 363 relative to whatever indentation the signature has. ``OuterScope`` lets you 364 change that so that the lambda body is indented one level relative to the scope 365 containing the lambda, regardless of where the lambda signature was placed. 366 367- Option ``IfMacros`` has been added. This lets you define macros that get 368 formatted like conditionals much like ``ForEachMacros`` get styled like 369 foreach loops. 370 371- ``git-clang-format`` no longer formats changes to symbolic links. (Fixes 372 https://llvm.org/PR46992.) 373 374- Makes ``PointerAligment: Right`` working with ``AlignConsecutiveDeclarations``. 375 (Fixes https://llvm.org/PR27353) 376 377- Option ``AlignArrayOfStructure`` has been added to allow for ordering array-like 378 initializers. 379 380- Support for formatting JSON file (\*.json) has been added to clang-format. 381 382libclang 383-------- 384 385- Make libclang SONAME independent from LLVM version. It will be updated only when 386 needed. Defined in CLANG_SONAME (clang/tools/libclang/CMakeLists.txt). 387 `More details <https://lists.llvm.org/pipermail/cfe-dev/2021-June/068423.html>`_ 388 389Static Analyzer 390--------------- 391 392.. 2407eb08a574 [analyzer] Update static analyzer to be support sarif-html 393 394- Add a new analyzer output type, ``sarif-html``, that outputs both HTML and 395 Sarif files. 396 397.. 90377308de6c [analyzer] Support allocClassWithName in OSObjectCStyleCast checker 398 399- Add support for ``allocClassWithName`` in OSObjectCStyleCast checker. 400 401.. cad9b7f708e2b2d19d7890494980c5e427d6d4ea: Print time taken to analyze each function 402 403- The option ``-analyzer-display-progress`` now also outputs analysis time for 404 each function. 405 406.. 9e02f58780ab8734e5d27a0138bd477d18ae64a1 [analyzer] Highlight arrows for currently selected event 407 408- For bug reports in HTML format, arrows are now highlighted for the currently 409 selected event. 410 411.. Deep Majumder's GSoC'21 412.. 80068ca6232b [analyzer] Fix for faulty namespace test in SmartPtrModelling 413.. d825309352b4 [analyzer] Handle std::make_unique 414.. 0cd98bef1b6f [analyzer] Handle std::swap for std::unique_ptr 415.. 13fe78212fe7 [analyzer] Handle << operator for std::unique_ptr 416.. 48688257c52d [analyzer] Model comparision methods of std::unique_ptr 417.. f8d3f47e1fd0 [analyzer] Updated comments to reflect D85817 418.. 21daada95079 [analyzer] Fix static_cast on pointer-to-member handling 419 420- While still in alpha, ``alpha.cplusplus.SmartPtr`` received numerous 421 improvements and nears production quality. 422 423.. 21daada95079 [analyzer] Fix static_cast on pointer-to-member handling 424.. 170c67d5b8cc [analyzer] Use the MacroExpansionContext for macro expansions in plists 425.. 02b51e5316cd [analyzer][solver] Redesign constraint ranges data structure 426.. 3085bda2b348 [analyzer][solver] Fix infeasible constraints (PR49642) 427.. 015c39882ebc [Analyzer] Infer 0 value when the divisible is 0 (bug fix) 428.. 90377308de6c [analyzer] Support allocClassWithName in OSObjectCStyleCast checker 429.. df64f471d1e2 [analyzer] DynamicSize: Store the dynamic size 430.. e273918038a7 [analyzer] Track leaking object through stores 431.. 61ae2db2d7a9 [analyzer] Adjust the reported variable name in retain count checker 432.. 50f17e9d3139 [analyzer] RetainCountChecker: Disable reference counting for OSMetaClass. 433 434- Various fixes and improvements, including modeling of casts (such as 435 ``std::bit_cast<>``), constraint solving, explaining bug-causing variable 436 values, macro expansion notes, modeling the size of dynamic objects and the 437 modeling and reporting of Objective C/C++ retain count related bugs. These 438 should reduce false positives and make the remaining reports more readable. 439 440.. _release-notes-ubsan: 441 442Undefined Behavior Sanitizer (UBSan) 443------------------------------------ 444 445Core Analysis Improvements 446========================== 447 448- ... 449 450New Issues Found 451================ 452 453- ... 454 455Python Binding Changes 456---------------------- 457 458The following methods have been added: 459 460- ... 461 462Significant Known Problems 463========================== 464 465Additional Information 466====================== 467 468A wide variety of additional information is available on the `Clang web 469page <https://clang.llvm.org/>`_. The web page contains versions of the 470API documentation which are up-to-date with the Git version of 471the source code. You can access versions of these documents specific to 472this release by going into the "``clang/docs/``" directory in the Clang 473tree. 474 475If you have any questions or comments about Clang, please feel free to 476contact us via the `mailing 477list <https://lists.llvm.org/mailman/listinfo/cfe-dev>`_. 478