The GCC developers are pleased to announce the release of GCC 15.1.

The C frontend now defaults to the GNU C23 dialect. Some code needs porting for this. Some remaining C23 features have been implemented, as well as some new C2Y features.

The C++ frontend now implements several further C++26 features, some missing C++23 bits, and defect report resolutions. The libstdc++ library now notably experimentally supports std and std.compat modules, more algorithms usable in constexpr functions, flat maps and sets, and std::format support for containers and other ranges.

GCC now implements the Clang [[clang::musttail]] and [[clang::flag_enum]] attributes and their GNU counterparts with the same meaning for the C family language frontends. Support for new counted_by and nonnull_if_nonzero attributes has been added too.

The Fortran frontend has experimental support for unsigned integers.

GCC 15.1 has new COBOL frontend, so far supported only on a few 64-bit targets.

OpenMP support now includes metadirectives, tile and unroll constructs, interop construct and dispatch construct.

The vectorizer can now vectorize loops with early exits when array or buffer sizes aren't statically known. At -O2 can now vectorize some cheaply vectorizable loops with unknown tripcount.

Some code that compiled successfully with older GCC versions might require source changes, see Porting to GCC 15 for details.

For details see GCC 15 Release Series Changes, New Features, and Fixes).