182 captures

07 Jul 2015 - 08 Apr 2025

Jul	SEP	Nov
	10
2014	2015	2016

success

fail

About this capture

COLLECTED BY

Organization: Alexa Crawls

Starting in 1996, Alexa Internet has been donating their crawl data to the Internet Archive. Flowing in every day, these data are added to the Wayback Machine after an embargo period.

Collection: Alexa Crawls

Starting in 1996, Alexa Internet has been donating their crawl data to the Internet Archive. Flowing in every day, these data are added to the Wayback Machine after an embargo period.

TIMESTAMPS

GCC 6 Release Series
Changes, New Features, and Fixes

Caveats

• The default mode for C++ is now -std=gnu++14 instead of -std=gnu++98.

General Optimizer Improvements

• UndefinedBehaviorSanitizer gained a new sanitization option, -fsanitize=bounds-strict, which enables strict checking of array bounds. In particular, it enables -fsanitize=bounds as well as instrumentation of flexible array member-like arrays.

New Languages and Language specific improvements

C family

• The C and C++ compilers now support attributes on enumerators. For instance, it is now possible to mark enumerators as deprecated:

  enum {
    newval,
    oldval __attribute__ ((deprecated ("too old")))
  };
  

• Initial support for precise diagnostic locations within strings:

  format-strings.c:3:14: warning: field width specifier '*' expects a matching 'int' argument [-Wformat=]
     printf("%*d");
              ^
  

• New command-line options have been added for the C and C++ compilers:
  • -Wshift-negative-value warns about left shifting a negative value.
  • -Wshift-overflow warns about left shift overflows. This warning is enabled by default. -Wshift-overflow=2 also warns about left-shifting 1 into the sign bit.
  • -Wtautological-compare warns if a self-comparison always evaluates to true or false. This warning is enabled by -Wall.
  • -Wnull-dereference warns if the compiler detects paths that trigger erroneous or undefined behavior due to dereferencing a null pointer. This option is only active when -fdelete-null-pointer-checks is active, which is enabled by optimizations in most targets. The precision of the warnings depends on the optimization options used.

C

• It is possible to disable warnings when an initialized field of a structure or a union with side effects is being overridden when using designated initializers via a new warning option -Woverride-init-side-effects.

C++

• The default mode has been changed to -std=gnu++14.
• C++ Concepts are now supported when compiling with -std=gnu++1z or -std=c++1z.

Runtime Library (libstdc++)

• Experimental support for C++17, including the following new features:
  • std::uncaught_exceptions function (this is also available for -std=gnu++NN modes);
  • new member functions try_emplace and insert_or_assign for unique_key maps;
  • non-member functions std::size, std::empty, and std::data for accessing containers and arrays;
  • std::shared_mutex;
  • std::void_t and std::bool_constant utilities.
• An experimental implementation of the File System TS.
• Experimental support for most features of the second version of the Library Fundamentals TS.

Fortran

• The MATMUL intrinsic is now inlined for straightforward cases if front-end optimization is active. The maximum size for inlining can be set to n with the -finline-matmul-limit=n option and turned off with -finline-matmul-llimit=0.
• The -Wconversion-extra option will warn about REAL constants which have excess precision for their kind.
• The -Winteger-division option has been added, which warns about divisions of integer constants which are truncated. This option is included in -Wall by default.

New Targets and Target Specific Improvements

AArch64

• The new command line options -march=native, -mcpu=native and -mtune=native are now available on native AArch64 GNU/Linux systems. Specifying these options will cause GCC to auto-detect the host CPU and rewrite these options to the optimal setting for that system. If GCC is unable to detect the host CPU these options have no effect.
• -fpic is now supported by the AArch64 target when generating code for the small code model (-mcmodel=small). The size of the global offset table (GOT) is limited to 28KiB under the LP64 SysV ABI , and 15KiB under the ILP32 SysV ABI.
• The AArch64 port now supports target attributes and pragmas. Please refer to the documentation for details of available attributes and pragmas as well as usage instructions.
• Link-time optimization across translation units with different target-specific options is now supported.

IA-32/x86-64

• Support for new AMD instructions monitorx and mwaitx has been added. This includes new intrinsic and built-in support. It is enabled through option -mmwaitx. The instructions monitorx and mwaitx implement the same functionality as the old monitor and mwait instructions. In addition mwaitx adds a configurable timer. The timer value is received as third argument and stored in register %ebx.

MSP430

• The MSP430 compiler now has the ability to automatically distribute code and data between low memory (addresses below 64K) and high memory. This only applies to parts that actually have both memory regions and only if the linker script for the part has been specifically set up to support this feature.

  A new attribute of either can be applied to both functions and data, and this tells the compiler to place the object into low memory if there is room and into high memory otherwise. Two other new attributes - lower and upper - can be used to explicitly state that an object should be placed in the specified memory region. If there is not enough left in that region the compilation will fail.

  Two new command-line options - -mcode-region=[lower|upper|either] and -mdata-region=[lower|upper|either] - can be used to tell the compiler what to do with objects that do not have one of these new attributes.

• A new configuration option ---with-advance-toolchain=at was added for PowerPC 64-bit GNU/Linux systems to use the header files, library files, and the dynamic linker from a specific Advance Toolchain release instead of the default versions that are provided by the GNU/Linux distribution. In general, this option is intended for the developers of GCC, and it is not intended for general use.

Other significant improvements

• The --enable-default-pie configure option enables generation of PIE by default.