.GCC 11.2.1 is available RHEL 9 is distributed with GCC version 11.2.1. Notable bug fixes and enhancements include: *General improvements* * GCC now defaults to the DWARF Version 5 debugging format. * Column numbers shown in diagnostics represent real column numbers by default and respect multicolumn characters. * The straight-line code vectorizer considers the whole function when vectorizing. * A series of conditional expressions that compare the same variable can be transformed into a switch statement if each of them contains a comparison expression. * Interprocedural optimization improvements: ** A new IPA-modref pass, controlled by the `-fipa-modref` option, tracks side effects of function calls and improves the precision of points-to analysis. ** The identical code folding pass, controlled by the `-fipa-icf` option, was significantly improved to increase the number of unified functions and reduce compile-time memory use. * Link-time optimization improvements: ** Link-time optimization (LTO) enables the compiler to perform various optimizations across all translation units of your program by using its intermediate representation at link time. For more information, see link:https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/9/html-single/developing_c_and_cpp_applications_in_rhel_9/index#ref_link-time-optimization_using-libraries-with-gcc[Link time optimization]. ** Memory allocation during linking was improved to reduce peak memory use. * Using a new `GCC_EXTRA_DIAGNOSTIC_OUTPUT` environment variable in IDEs, you can request machine-readable “fix-it hints” without adjusting build flags. * The static analyzer, run by the `-fanalyzer` option, is improved significantly with numerous bug fixes and enhancements provided. *Language-specific improvements* *C family* * C and C++ compilers support non-rectangular loop nests in OpenMP constructs and the allocator routines of the OpenMP 5.0 specification. * Attributes: ** The new `no_stack_protector` attribute marks functions that should not be instrumented with stack protection (`-fstack-protector`). ** The improved `malloc` attribute can be used to identify allocator and deallocator API pairs. * New warnings: ** `-Wsizeof-array-div`, enabled by the `-Wall` option, warns about divisions of two `sizeof` operators when the first one is applied to an array and the divisor does not equal the size of the array element. ** `-Wstringop-overread`, enabled by default, warns about calls to string functions that try to read past the end of the arrays passed to them as arguments. * Enhanced warnings: ** `-Wfree-nonheap-object` detects more instances of calls to deallocation functions with pointers not returned from a dynamic memory allocation function. ** `-Wmaybe-uninitialized` diagnoses the passing of pointers and references to uninitialized memory to functions that take `const`-qualified arguments. ** `-Wuninitialized` detects reads from uninitialized dynamically allocated memory. *C* * Several new features from the upcoming C2X revision of the ISO C standard are supported with the `-std=c2x` and `-std=gnu2x` options. For example: ** The `[[nodiscard]]` standard attribute is supported. ** The `__has_c_attribute` preprocessor operator is supported. ** Labels may appear before declarations and at the end of a compound statement. *C++* * The default mode is changed to `-std=gnu++17`. * The pass:[C++] library `pass:[libstdc++]` has improved C++17 support now. * Several new pass:[C++20] features are implemented. Note that pass:[C++20] support is experimental. + For more information about the features, see link:https://gcc.gnu.org/projects/cxx-status.html#cxx20[C++20 Language Features]. * The pass:[C++] front end has experimental support for some of the upcoming pass:[C++23] draft features. * New warnings: ** `-Wctad-maybe-unsupported`, disabled by default, warns about performing class template argument deduction on a type with no deduction guides. ** `-Wrange-loop-construct`, enabled by `-Wall`, warns when a range-based for loop is creating unnecessary and resource inefficient copies. ** `-Wmismatched-new-delete`, enabled by `-Wall`, warns about calls to operator delete with pointers returned from mismatched forms of operator new or from other mismatched allocation functions. ** `-Wvexing-parse`, enabled by default, warns about the most vexing parse rule: the cases when a declaration looks like a variable definition, but the C++ language requires it to be interpreted as a function declaration. *Architecture-specific improvements* *The 64-bit ARM architecture* * The Armv8-R architecture is supported through the `-march=armv8-r` option. * GCC can autovectorize operations performing addition, subtraction, multiplication, and the accumulate and subtract variants on complex numbers. *AMD and Intel 64-bit architectures* //* The following Intel CPUs are recognized: Sapphire Rapids, Alder Lake, and Rocket Lake. * New ISA extension support for Intel AVX-VNNI is added. The `-mavxvnni` compiler switch controls the AVX-VNNI intrinsics. * AMD CPUs based on the znver3 core are supported with the new `-march=znver3` option. * Three microarchitecture levels defined in link:https://gitlab.com/x86-psABIs/x86-64-ABI[the x86-64 psABI supplement] are supported with the new `-march=x86-64-v2`, `-march=x86-64-v3`, and `-march=x86-64-v4` options. *IBM Z architectures* * GCC 11.2.1 defaults to the IBM z14 processor. *IBM Power Systems* * GCC 11.2.1 defaults to the IBM POWER9 processor. * The GCC compiler now supports POWER10 instructions with the new `-mcpu=power10` command-line option