Major New Features¶

• Experimental support for C++ for OpenCL has been added.

Non-comprehensive list of changes in this release¶

• The __VERSION__ macro has been updated. Previously this macro contained the string ‘4.2.1 Compatible’ to achieve compatibility with GCC 4.2.1, but that should no longer be necessary. However, to retrieve Clang’s version, please favor the one of the macro defined in clang namespaced version macros.

New Compiler Flags¶

• -ftime-trace and ftime-trace-granularity=N Emits flame chart style compilation time report in chrome://tracing and speedscope.app compatible format. A trace .json file is written next to the compiled object file, containing hierarchical time information about frontend activities (file parsing, template instantiation) and backend activities (modules and functions being optimized, optimization passes).

Modified Compiler Flags¶

• clang -dumpversion now returns the version of Clang itself.

Windows Support¶

• clang-cl now treats non-existent files as possible typos for flags, clang-cl /diagnostic:caret /c test.cc for example now produces clang: error: no such file or directory: '/diagnostic:caret'; did you mean '/diagnostics:caret'?
• clang now parses the __declspec(allocator) specifier and generates debug information, so that memory usage can be tracked in Visual Studio.
• The -print-search-dirs option now separates elements with semicolons, as is the norm for path lists on Windows
• Improved handling of dllexport in conjunction with explicit template instantiations for MinGW, to allow building a shared libc++ for MinGW without --export-all-symbols to override the dllexport attributes

C Language Changes in Clang¶

• The __FILE_NAME__ macro has been added as a Clang specific extension supported in all C-family languages. This macro is similar to __FILE__ except it will always provide the last path component when possible.
• Initial support for asm goto statements (a GNU C extension) has been added for control flow from inline assembly to labels. The main consumers of this construct are the Linux kernel (CONFIG_JUMP_LABEL=y) and glib. There are still a few unsupported corner cases in Clang’s integrated assembler and IfConverter. Please file bugs for any issues you run into.

C++ Language Changes in Clang¶

• Support for the address space attribute in various C++ features was improved, refer to C++ for OpenCL for more details. The following features deviated from OpenCL:
  1. Address spaces as method qualifiers are not accepted yet;
  2. There is no address space deduction.

Objective-C Language Changes in Clang¶

• Fixed encoding of ObjC pointer types that are pointers to typedefs.

  typedef NSArray<NSObject *> MyArray;
  
  // clang used to encode this as "^{NSArray=#}" instead of "@".
  const char *s0 = @encode(MyArray *);
  

OpenCL Kernel Language Changes in Clang¶

OpenMP Support in Clang¶

• Added emission of the debug information for NVPTX target devices.

CUDA Support in Clang¶

• Added emission of the debug information for the device code.

Internal API Changes¶

These are major API changes that have happened since the 8.0.0 release of Clang. If upgrading an external codebase that uses Clang as a library, this section should help get you past the largest hurdles of upgrading.

Build System Changes¶

These are major changes to the build system that have happened since the 8.0.0 release of Clang. Users of the build system should adjust accordingly.

• In 8.0.0 and below, the install-clang-headers target would install clang’s resource directory headers. This installation is now performed by the install-clang-resource-headers target. Users of the old install-clang-headers target should switch to the new install-clang-resource-headers target. The install-clang-headers target now installs clang’s API headers (corresponding to its libraries), which is consistent with the install-llvm-headers target.
• In 9.0.0 and later Clang added a new target on Linux/Unix systems, clang-cpp, which generates a shared library comprised of all the clang component libraries and exporting the clang C++ APIs. Additionally the build system gained the new “CLANG_LINK_CLANG_DYLIB” option, which defaults Off, and when set to On, will force clang (and clang-based tools) to link the clang-cpp library instead of statically linking clang’s components. This option will reduce the size of binary distributions at the expense of compiler performance.

clang-format¶

• Add language support for clang-formatting C# files.
• Add Microsoft coding style to encapsulate default C# formatting style.
• Added new option PPDIS_BeforeHash (in configuration: BeforeHash) to IndentPPDirectives which indents preprocessor directives before the hash.
• Added new option AlignConsecutiveMacros to align the C/C++ preprocessor macros of consecutive lines.

libclang¶

• When CINDEXTEST_INCLUDE_ATTRIBUTED_TYPES is not provided when making a CXType, the equivalent type of the AttributedType is returned instead of the modified type if the user does not want attribute sugar. The equivalent type represents the minimally-desugared type which the AttributedType is canonically equivalent to.

Static Analyzer¶

• Fixed a bug where an incorrect checker name would be displayed for a bug report.
• New checker: security.insecureAPI.DeprecatedOrUnsafeBufferHandling to detect uses of unsafe/deprecated buffer handling functions for C code using the C11 standard or newer.
• New checker: osx.MIGChecker to find violations of the Mach Interface Generator calling convention
• New checker: optin.osx.OSObjectCStyleCast to find C-style casts of of XNU libkern OSObjects
• New package: apiModeling.llvm contains modeling checkers to improve the accuracy of reports on LLVM’s own codebase.
• The Static Analyzer received developer documentation.
• The UninitializedObject checker is now considered as stable. (moved from the alpha.cplusplus to the optin.cplusplus package)
• New frontend flags: The list of available checkers are now split into 3 different frontend flags:
  • -analyzer-checker-help: The list of user-facing, stable checkers.
  • -analyzer-checker-help-alpha: The list of in-development checkers not yet advised to be turned on.
  • -analyzer-checker-help-developer: Checkers never meant to be enabled/disabled by hand + development checkers.
• New frontend flags: While they have always been around, for the first time, checker and package options are listable:
  • -analyzer-checker-option-help: The list of user-facing, stable checker and package options.
  • -analyzer-checker-option-help-alpha: The list of in-development checker options not yet advised to be used.
  • -analyzer-checker-option-help-developer: Options never meant to be enabled/disabled by hand + development options.
• New frontend flag: -analyzer-werror to turn analyzer warnings into errors.
• Numerous fixes to increase the stability of the experimental cross translation unit analysis (CTU).
• CTU now handles virtual functions as well.