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NEWS
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This file contains information about GCC releases which has been generated
automatically from the online release notes. It covers releases of GCC
(and the former EGCS project) since EGCS 1.0, on the line of development
that led to GCC 3. For information on GCC 2.8.1 and older releases of GCC 2,
see ONEWS.
======================================================================
http://gcc.gnu.org/gcc-4.8/index.html
GCC 4.8 Release Series
May 22, 2014
The [1]GNU project and the GCC developers are pleased to announce the
release of GCC 4.8.3.
This release is a bug-fix release, containing fixes for regressions in
GCC 4.8.2 relative to previous releases of GCC.
Release History
GCC 4.8.3
May 22, 2014 ([2]changes, [3]documentation)
GCC 4.8.2
October 16, 2013 ([4]changes, [5]documentation)
GCC 4.8.1
May 31, 2013 ([6]changes, [7]documentation)
GCC 4.8.0
March 22, 2013 ([8]changes, [9]documentation)
References and Acknowledgements
GCC used to stand for the GNU C Compiler, but since the compiler
supports several other languages aside from C, it now stands for the
GNU Compiler Collection.
A list of [10]successful builds is updated as new information becomes
available.
The GCC developers would like to thank the numerous people that have
contributed new features, improvements, bug fixes, and other changes as
well as test results to GCC. This [11]amazing group of volunteers is
what makes GCC successful.
For additional information about GCC please refer to the [12]GCC
project web site or contact the [13]GCC development mailing list.
To obtain GCC please use [14]our mirror sites or [15]our SVN server.
For questions related to the use of GCC, please consult these web
pages and the [16]GCC manuals. If that fails, the
[17][email protected] mailing list might help. Comments on these
web pages and the development of GCC are welcome on our developer
list at [18][email protected]. All of [19]our lists have public
archives.
Copyright (C) [20]Free Software Foundation, Inc. Verbatim copying and
distribution of this entire article is permitted in any medium,
provided this notice is preserved.
These pages are [21]maintained by the GCC team. Last modified
2014-05-22[22].
References
1. http://www.gnu.org/
2. http://gcc.gnu.org/gcc-4.8/changes.html
3. http://gcc.gnu.org/onlinedocs/4.8.3/
4. http://gcc.gnu.org/gcc-4.8/changes.html
5. http://gcc.gnu.org/onlinedocs/4.8.2/
6. http://gcc.gnu.org/gcc-4.8/changes.html
7. http://gcc.gnu.org/onlinedocs/4.8.1/
8. http://gcc.gnu.org/gcc-4.8/changes.html
9. http://gcc.gnu.org/onlinedocs/4.8.0/
10. http://gcc.gnu.org/gcc-4.8/buildstat.html
11. http://gcc.gnu.org/onlinedocs/gcc/Contributors.html
12. http://gcc.gnu.org/index.html
13. mailto:[email protected]
14. http://gcc.gnu.org/mirrors.html
15. http://gcc.gnu.org/svn.html
16. http://gcc.gnu.org/onlinedocs/
17. mailto:[email protected]
18. mailto:[email protected]
19. http://gcc.gnu.org/lists.html
20. http://www.fsf.org/
21. http://gcc.gnu.org/about.html
22. http://validator.w3.org/check/referer
======================================================================
http://gcc.gnu.org/gcc-4.8/changes.html
GCC 4.8 Release Series
Changes, New Features, and Fixes
Caveats
GCC now uses C++ as its implementation language. This means that to
build GCC from sources, you will need a C++ compiler that understands
C++ 2003. For more details on the rationale and specific changes,
please refer to the [1]C++ conversion page.
To enable the Graphite framework for loop optimizations you now need
CLooG version 0.18.0 and ISL version 0.11.1. Both can be obtained from
the [2]GCC infrastructure directory. The installation manual contains
more information about requirements to build GCC.
GCC now uses a more aggressive analysis to derive an upper bound for
the number of iterations of loops using constraints imposed by language
standards. This may cause non-conforming programs to no longer work as
expected, such as SPEC CPU 2006 464.h264ref and 416.gamess. A new
option, -fno-aggressive-loop-optimizations, was added to disable this
aggressive analysis. In some loops that have known constant number of
iterations, but undefined behavior is known to occur in the loop before
reaching or during the last iteration, GCC will warn about the
undefined behavior in the loop instead of deriving lower upper bound of
the number of iterations for the loop. The warning can be disabled with
-Wno-aggressive-loop-optimizations.
On ARM, a bug has been fixed in GCC's implementation of the AAPCS rules
for the layout of vectors that could lead to wrong code being
generated. Vectors larger than 8 bytes in size are now by default
aligned to an 8-byte boundary. This is an ABI change: code that makes
explicit use of vector types may be incompatible with binary objects
built with older versions of GCC. Auto-vectorized code is not affected
by this change.
On AVR, support has been removed for the command-line option
-mshort-calls deprecated in GCC 4.7.
On AVR, the configure option --with-avrlibc supported since GCC 4.7.2
is turned on per default for all non-RTEMS configurations. This option
arranges for a better integration of [3]AVR Libc with avr-gcc. For
technical details, see [4]PR54461. To turn off the option in non-RTEMS
configurations, use --with-avrlibc=no. If the compiler is configured
for RTEMS, the option is always turned off.
More information on porting to GCC 4.8 from previous versions of GCC
can be found in the [5]porting guide for this release.
General Optimizer Improvements (and Changes)
* DWARF4 is now the default when generating DWARF debug information.
When -g is used on a platform that uses DWARF debugging
information, GCC will now default to -gdwarf-4
-fno-debug-types-section.
GDB 7.5, Valgrind 3.8.0 and elfutils 0.154 debug information
consumers support DWARF4 by default. Before GCC 4.8 the default
version used was DWARF2. To make GCC 4.8 generate an older DWARF
version use -g together with -gdwarf-2 or -gdwarf-3. The default
for Darwin and VxWorks is still -gdwarf-2 -gstrict-dwarf.
* A new general optimization level, -Og, has been introduced. It
addresses the need for fast compilation and a superior debugging
experience while providing a reasonable level of runtime
performance. Overall experience for development should be better
than the default optimization level -O0.
* A new option -ftree-partial-pre was added to control the partial
redundancy elimination (PRE) optimization. This option is enabled
by default at the -O3 optimization level, and it makes PRE more
aggressive.
* The option -fconserve-space has been removed; it was no longer
useful on most targets since GCC supports putting variables into
BSS without making them common.
* The struct reorg and matrix reorg optimizations (command-line
options -fipa-struct-reorg and -fipa-matrix-reorg) have been
removed. They did not always work correctly, nor did they work with
link-time optimization (LTO), hence were only applicable to
programs consisting of a single translation unit.
* Several scalability bottle-necks have been removed from GCC's
optimization passes. Compilation of extremely large functions, e.g.
due to the use of the flatten attribute in the "Eigen" C++ linear
algebra templates library, is significantly faster than previous
releases of GCC.
* Link-time optimization (LTO) improvements:
+ LTO partitioning has been rewritten for better reliability and
maintanibility. Several important bugs leading to link
failures have been fixed.
* Interprocedural optimization improvements:
+ A new symbol table has been implemented. It builds on existing
callgraph and varpool modules and provide a new API. Unusual
symbol visibilities and aliases are handled more consistently
leading to, for example, more aggressive unreachable code
removal with LTO.
+ The inline heuristic can now bypass limits on the size of of
inlined functions when the inlining is particularly
profitable. This happens, for example, when loop bounds or
array strides get propagated.
+ Values passed through aggregates (either by value or
reference) are now propagated at the inter-procedural level
leading to better inlining decisions (for example in the case
of Fortran array descriptors) and devirtualization.
* [6]AddressSanitizer , a fast memory error detector, has been added
and can be enabled via -fsanitize=address. Memory access
instructions will be instrumented to detect heap-, stack-, and
global-buffer overflow as well as use-after-free bugs. To get nicer
stacktraces, use -fno-omit-frame-pointer. The AddressSanitizer is
available on IA-32/x86-64/x32/PowerPC/PowerPC64 GNU/Linux and on
x86-64 Darwin.
* [7]ThreadSanitizer has been added and can be enabled via
-fsanitize=thread. Instructions will be instrumented to detect data
races. The ThreadSanitizer is available on x86-64 GNU/Linux.
* A new local register allocator (LRA) has been implemented, which
replaces the 26 year old reload pass and improves generated code
quality. For now it is active on the IA-32 and x86-64 targets.
* Support for transactional memory has been implemented on the
following architectures: IA-32/x86-64, ARM, PowerPC, SH, SPARC, and
Alpha.
New Languages and Language specific improvements
C family
* Each diagnostic emitted now includes the original source line and a
caret '^' indicating the column. The option
-fno-diagnostics-show-caret suppresses this information.
* The option -ftrack-macro-expansion=2 is now enabled by default.
This allows the compiler to display the macro expansion stack in
diagnostics. Combined with the caret information, an example
diagnostic showing these two features is:
t.c:1:94: error: invalid operands to binary < (have `struct mystruct' and `float
')
#define MYMAX(A,B) __extension__ ({ __typeof__(A) __a = (A); __typeof__(B) _
_b = (B); __a < __b ? __b : __a; })
^
t.c:7:7: note: in expansion of macro 'MYMAX'
X = MYMAX(P, F);
^
* A new -Wsizeof-pointer-memaccess warning has been added (also
enabled by -Wall) to warn about suspicious length parameters to
certain string and memory built-in functions if the argument uses
sizeof. This warning warns e.g. about memset (ptr, 0, sizeof
(ptr)); if ptr is not an array, but a pointer, and suggests a
possible fix, or about memcpy (&foo, ptr, sizeof (&foo));.
* The new option -Wpedantic is an alias for -pedantic, which is now
deprecated. The forms -Wno-pedantic, -Werror=pedantic, and
-Wno-error=pedantic work in the same way as for any other -W
option. One caveat is that -Werror=pedantic is not equivalent to
-pedantic-errors, since the latter makes into errors some warnings
that are not controlled by -Wpedantic, and the former only affects
diagnostics that are disabled when using -Wno-pedantic.
* The option -Wshadow no longer warns if a declaration shadows a
function declaration, unless the former declares a function or
pointer to function, because this is [8]a common and valid case in
real-world code.
C++
* G++ now implements the [9]C++11 thread_local keyword; this differs
from the GNU __thread keyword primarily in that it allows dynamic
initialization and destruction semantics. Unfortunately, this
support requires a run-time penalty for references to
non-function-local thread_local variables defined in a different
translation unit even if they don't need dynamic initialization, so
users may want to continue to use __thread for TLS variables with
static initialization semantics.
If the programmer can be sure that no use of the variable in a
non-defining TU needs to trigger dynamic initialization (either
because the variable is statically initialized, or a use of the
variable in the defining TU will be executed before any uses in
another TU), they can avoid this overhead with the
-fno-extern-tls-init option.
OpenMP threadprivate variables now also support dynamic
initialization and destruction by the same mechanism.
* G++ now implements the [10]C++11 attribute syntax, e.g.
[[noreturn]] void f();
and also the alignment specifier, e.g.
alignas(double) int i;
* G++ now implements [11]C++11 inheriting constructors, e.g.
struct A { A(int); };
struct B: A { using A::A; }; // defines B::B(int)
B b(42); // OK
* As of GCC 4.8.1, G++ implements the change to decltype semantics
from [12]N3276.
struct A f();
decltype(f()) g(); // OK, return type of f() is not required to be complete.
* As of GCC 4.8.1, G++ implements [13]C++11 ref-qualifiers, e.g.
struct A { int f() &; };
int i = A().f(); // error, f() requires an lvalue object
* G++ now supports a -std=c++1y option for experimentation with
features proposed for the next revision of the standard, expected
around 2014. Currently the only difference from -std=c++11 is
support for return type deduction in normal functions, as proposed
in [14]N3386. Status of C++1y features in GCC 4.8 can be found
[15]here.
* The G++ namespace association extension, __attribute ((strong)),
has been deprecated. Inline namespaces should be used instead.
* G++ now supports a -fext-numeric-literal option to control whether
GNU numeric literal suffixes are accepted as extensions or
processed as C++11 user-defined numeric literal suffixes. The flag
is on (use suffixes for GNU literals) by default for -std=gnu++*,
and -std=c++98. The flag is off (use suffixes for user-defined
literals) by default for -std=c++11 and later.
Runtime Library (libstdc++)
* [16]Improved experimental support for the new ISO C++ standard,
C++11, including:
+ forward_list meets the allocator-aware container requirements;
+ this_thread::sleep_for(), this_thread::sleep_until() and
this_thread::yield() are defined without requiring the
configure option --enable-libstdcxx-time;
* Improvements to <random>:
+ SSE optimized normal_distribution.
+ Use of hardware RNG instruction for random_device on new x86
processors (requires the assembler to support the
instruction.)
and <ext/random>:
+ New random number engine simd_fast_mersenne_twister_engine
with an optimized SSE implementation.
+ New random number distributions beta_distribution,
normal_mv_distribution, rice_distribution,
nakagami_distribution, pareto_distribution, k_distribution,
arcsine_distribution, hoyt_distribution.
* Added --disable-libstdcxx-verbose configure option to disable
diagnostic messages issued when a process terminates abnormally.
This may be useful for embedded systems to reduce the size of
executables that link statically to the library.
Fortran
* Compatibility notice:
+ Module files: The version of module files (.mod) has been
incremented. Fortran MODULEs compiled by earlier GCC versions
have to be recompiled, when they are USEd by files compiled
with GCC 4.8. GCC 4.8 is not able to read .mod files created
by earlier versions; attempting to do so gives an error
message.
Note: The ABI of the produced assembler data itself has not
changed; object files and libraries are fully compatible with
older versions except as noted below.
+ ABI: Some internal names (used in the assembler/object file)
have changed for symbols declared in the specification part of
a module. If an affected module - or a file using it via use
association - is recompiled, the module and all files which
directly use such symbols have to be recompiled as well. This
change only affects the following kind of module symbols:
o Procedure pointers. Note: C-interoperable function
pointers (type(c_funptr)) are not affected nor are
procedure-pointer components.
o Deferred-length character strings.
* The [17]BACKTRACE intrinsic subroutine has been added. It shows a
backtrace at an arbitrary place in user code; program execution
continues normally afterwards.
* The [18]-Wc-binding-type warning option has been added (disabled by
default). It warns if the a variable might not be C interoperable;
in particular, if the variable has been declared using an intrinsic
type with default kind instead of using a kind parameter defined
for C interoperability in the intrinsic ISO_C_Binding module.
Before, this warning was always printed. The -Wc-binding-type
option is enabled by -Wall.
* The [19]-Wrealloc-lhs and -Wrealloc-lhs-all warning command-line
options have been added, which diagnose when code to is inserted
for automatic (re)allocation of a variable during assignment. This
option can be used to decide whether it is safe to use
[20]-fno-realloc-lhs. Additionally, it can be used to find
automatic (re)allocation in hot loops. (For arrays, replacing
"var=" by "var(:)=" disables the automatic reallocation.)
* The [21]-Wcompare-reals command-line option has been added. When
this is set, warnings are issued when comparing REAL or COMPLEX
types for equality and inequality; consider replacing a == b by
abs(a -b) < eps with a suitable eps. -Wcompare-reals is enabled by
-Wextra.
* The [22]-Wtarget-lifetime command-line option has been added
(enabled with -Wall), which warns if the pointer in a pointer
assignment might outlive its target.
* Reading floating point numbers which use "q" for the exponential
(such as 4.0q0) is now supported as vendor extension for better
compatibility with old data files. It is strongly recommended to
use for I/O the equivalent but standard conforming "e" (such as
4.0e0).
(For Fortran source code, consider replacing the "q" in
floating-point literals by a kind parameter (e.g. 4.0e0_qp with a
suitable qp). Note that - in Fortran source code - replacing "q" by
a simple "e" is not equivalent.)
* The GFORTRAN_TMPDIR environment variable for specifying a
non-default directory for files opened with STATUS="SCRATCH", is
not used anymore. Instead gfortran checks the POSIX/GNU standard
TMPDIR environment variable. If TMPDIR is not defined, gfortran
falls back to other methods to determine the directory for
temporary files as documented in the [23]user manual.
* [24]Fortran 2003:
+ Support for unlimited polymorphic variables (CLASS(*)) has
been added. Nonconstant character lengths are not yet
supported.
* [25]TS 29113:
+ Assumed types (TYPE(*)) are now supported.
+ Experimental support for assumed-rank arrays (dimension(..))
has been added. Note that currently gfortran's own array
descriptor is used, which is different from the one defined in
TS29113, see [26]gfortran's header file or use the [27]Chasm
Language Interoperability Tools.
Go
* GCC 4.8.2 provides a complete implementation of the Go 1.1.2
release.
* GCC 4.8.0 and 4.8.1 implement a preliminary version of the Go 1.1
release. The library support is not quite complete.
* Go has been tested on GNU/Linux and Solaris platforms for various
processors including x86, x86_64, PowerPC, SPARC, and Alpha. It may
work on other platforms as well.
New Targets and Target Specific Improvements
AArch64
* A new port has been added to support AArch64, the new 64-bit
architecture from ARM. Note that this is a separate port from the
existing 32-bit ARM port.
* The port provides initial support for the Cortex-A53 and the
Cortex-A57 processors with the command line options
-mcpu=cortex-a53 and -mcpu=cortex-a57.
ARM
* Initial support has been added for the AArch32 extensions defined
in the ARMv8 architecture.
* Code generation improvements for the Cortex-A7 and Cortex-A15 CPUs.
* A new option, -mcpu=marvell-pj4, has been added to generate code
for the Marvell PJ4 processor.
* The compiler can now automatically generate the VFMA, VFMS, REVSH
and REV16 instructions.
* A new vectorizer cost model for Advanced SIMD configurations to
improve the auto-vectorization strategies used.
* The scheduler now takes into account the number of live registers
to reduce the amount of spilling that can occur. This should
improve code performance in large functions. The limit can be
removed by using the option -fno-sched-pressure.
* Improvements have been made to the Marvell iWMMX code generation
and support for the iWMMX2 SIMD unit has been added. The option
-mcpu=iwmmxt2 can be used to enable code generation for the latter.
* A number of code generation improvements for Thumb2 to reduce code
size when compiling for the M-profile processors.
* The RTEMS (arm-rtems) port has been updated to use the EABI.
* Code generation support for the old FPA and Maverick floating-point
architectures has been removed. Ports that previously relied on
these features have also been removed. This includes the targets:
+ arm*-*-linux-gnu (use arm*-*-linux-gnueabi)
+ arm*-*-elf (use arm*-*-eabi)
+ arm*-*-uclinux* (use arm*-*-uclinux*eabi)
+ arm*-*-ecos-elf (no alternative)
+ arm*-*-freebsd (no alternative)
+ arm*-wince-pe* (no alternative).
AVR
* Support for the "Embedded C" fixed-point has been added. For
details, see the [28]GCC wiki and the [29]user manual. The support
is not complete.
* A new print modifier %r for register operands in inline assembler
is supported. It will print the raw register number without the
register prefix 'r':
/* Return the most significant byte of 'val', a 64-bit value. */
unsigned char msb (long long val)
{
unsigned char c;
__asm__ ("mov %0, %r1+7" : "=r" (c) : "r" (val));
return c;
}
The inline assembler in this example will generate code like
mov r24, 8+7
provided c is allocated to R24 and val is allocated to R8...R15.
This works because the GNU assembler accepts plain register numbers
without register prefix.
* Static initializers with 3-byte symbols are supported now:
extern const __memx char foo;
const __memx void *pfoo = &foo;
This requires at least Binutils 2.23.
IA-32/x86-64
* Allow -mpreferred-stack-boundary=3 for the x86-64 architecture with
SSE extensions disabled. Since the x86-64 ABI requires 16 byte
stack alignment, this is ABI incompatible and intended to be used
in controlled environments where stack space is an important
limitation. This option will lead to wrong code when functions
compiled with 16 byte stack alignment (such as functions from a
standard library) are called with misaligned stack. In this case,
SSE instructions may lead to misaligned memory access traps. In
addition, variable arguments will be handled incorrectly for 16
byte aligned objects (including x87 long double and __int128),
leading to wrong results. You must build all modules with
-mpreferred-stack-boundary=3, including any libraries. This
includes the system libraries and startup modules.
* Support for the new Intel processor codename Broadwell with RDSEED,
ADCX, ADOX, PREFETCHW is available through -madx, -mprfchw,
-mrdseed command-line options.
* Support for the Intel RTM and HLE intrinsics, built-in functions
and code generation is available via -mrtm and -mhle.
* Support for the Intel FXSR, XSAVE and XSAVEOPT instruction sets.
Intrinsics and built-in functions are available via -mfxsr, -mxsave
and -mxsaveopt respectively.
* New -maddress-mode=[short|long] options for x32.
-maddress-mode=short overrides default 64-bit addresses to 32-bit
by emitting the 0x67 address-size override prefix. This is the
default address mode for x32.
* New built-in functions to detect run-time CPU type and ISA:
+ A built-in function __builtin_cpu_is has been added to detect
if the run-time CPU is of a particular type. It returns a
positive integer on a match and zero otherwise. It accepts one
string literal argument, the CPU name. For example,
__builtin_cpu_is("westmere") returns a positive integer if the
run-time CPU is an Intel Core i7 Westmere processor. Please
refer to the [30]user manual for the list of valid CPU names
recognized.
+ A built-in function __builtin_cpu_supports has been added to
detect if the run-time CPU supports a particular ISA feature.
It returns a positive integer on a match and zero otherwise.
It accepts one string literal argument, the ISA feature. For
example, __builtin_cpu_supports("ssse3") returns a positive
integer if the run-time CPU supports SSSE3 instructions.
Please refer to the [31]user manual for the list of valid ISA
names recognized.
Caveat: If these built-in functions are called before any static
constructors are invoked, like during IFUNC initialization, then
the CPU detection initialization must be explicitly run using this
newly provided built-in function, __builtin_cpu_init. The
initialization needs to be done only once. For example, this is how
the invocation would look like inside an IFUNC initializer:
static void (*some_ifunc_resolver(void))(void)
{
__builtin_cpu_init();
if (__builtin_cpu_is("amdfam10h") ...
if (__builtin_cpu_supports("popcnt") ...
}
* Function Multiversioning Support with G++:
It is now possible to create multiple function versions each
targeting a specific processor and/or ISA. Function versions have
the same signature but different target attributes. For example,
here is a program with function versions:
__attribute__ ((target ("default")))
int foo(void)
{
return 1;
}
__attribute__ ((target ("sse4.2")))
int foo(void)
{
return 2;
}
int main (void)
{
int (*p) = &foo;
assert ((*p)() == foo());
return 0;
}
Please refer to this [32]wiki for more information.
* The x86 back end has been improved to allow option -fschedule-insns
to work reliably. This option can be used to schedule instructions
better and leads to improved performace in certain cases.
* Windows MinGW-w64 targets (*-w64-mingw*) require at least r5437
from the Mingw-w64 trunk.
* Support for new AMD family 15h processors (Steamroller core) is now
available through the -march=bdver3 and -mtune=bdver3 options.
* Support for new AMD family 16h processors (Jaguar core) is now
available through the -march=btver2 and -mtune=btver2 options.
FRV
* This target now supports the -fstack-usage command-line option.
MIPS
* GCC can now generate code specifically for the R4700, Broadcom XLP
and MIPS 34kn processors. The associated -march options are
-march=r4700, -march=xlp and -march=34kn respectively.
* GCC now generates better DSP code for MIPS 74k cores thanks to
further scheduling optimizations.
* The MIPS port now supports the -fstack-check option.
* GCC now passes the -mmcu and -mno-mcu options to the assembler.
* Previous versions of GCC would silently accept -fpic and -fPIC for
-mno-abicalls targets like mips*-elf. This combination was not
intended or supported, and did not generate position-independent
code. GCC 4.8 now reports an error when this combination is used.
PowerPC / PowerPC64 / RS6000
* SVR4 configurations (GNU/Linux, FreeBSD, NetBSD) no longer save,
restore or update the VRSAVE register by default. The respective
operating systems manage the VRSAVE register directly.
* Large TOC support has been added for AIX through the command line
option -mcmodel=large.
* Native Thread-Local Storage support has been added for AIX.
* VMX (Altivec) and VSX instruction sets now are enabled implicitly
when targetting processors that support those hardware features on
AIX 6.1 and above.
RX
* This target will now issue a warning message whenever multiple fast
interrupt handlers are found in the same compilation unit. This
feature can be turned off by the new
-mno-warn-multiple-fast-interrupts command-line option.
S/390, System z
* Support for the IBM zEnterprise zEC12 processor has been added.
When using the -march=zEC12 option, the compiler will generate code
making use of the following new instructions:
+ load and trap instructions
+ 2 new compare and trap instructions
+ rotate and insert selected bits - without CC clobber
The -mtune=zEC12 option enables zEC12 specific instruction
scheduling without making use of new instructions.
* Register pressure sensitive instruction scheduling is enabled by
default.
* The ifunc function attribute is enabled by default.
* memcpy and memcmp invokations on big memory chunks or with run time
lengths are not generated inline anymore when tuning for z10 or
higher. The purpose is to make use of the IFUNC optimized versions
in Glibc.
SH
* The default alignment settings have been reduced to be less
aggressive. This results in more compact code for optimization
levels other than -Os.
* Improved support for the __atomic built-in functions:
+ A new option -matomic-model=model selects the model for the
generated atomic sequences. The following models are
supported:
soft-gusa
Software gUSA sequences (SH3* and SH4* only). On
SH4A targets this will now also partially utilize
the movco.l and movli.l instructions. This is the
default when the target is sh3*-*-linux* or
sh4*-*-linux*.
hard-llcs
Hardware movco.l / movli.l sequences (SH4A only).
soft-tcb
Software thread control block sequences.
soft-imask
Software interrupt flipping sequences (privileged
mode only). This is the default when the target is
sh1*-*-linux* or sh2*-*-linux*.
none
Generates function calls to the respective __atomic
built-in functions. This is the default for SH64
targets or when the target is not sh*-*-linux*.
+ The option -msoft-atomic has been deprecated. It is now an
alias for -matomic-model=soft-gusa.
+ A new option -mtas makes the compiler generate the tas.b
instruction for the __atomic_test_and_set built-in function
regardless of the selected atomic model.
+ The __sync functions in libgcc now reflect the selected atomic
model when building the toolchain.
* Added support for the mov.b and mov.w instructions with
displacement addressing.
* Added support for the SH2A instructions movu.b and movu.w.
* Various improvements to code generated for integer arithmetic.
* Improvements to conditional branches and code that involves the T
bit. A new option -mzdcbranch tells the compiler to favor
zero-displacement branches. This is enabled by default for SH4*
targets.
* The pref instruction will now be emitted by the __builtin_prefetch
built-in function for SH3* targets.
* The fmac instruction will now be emitted by the fmaf standard
function and the __builtin_fmaf built-in function.
* The -mfused-madd option has been deprecated in favor of the
machine-independent -ffp-contract option. Notice that the fmac
instruction will now be generated by default for expressions like a
* b + c. This is due to the compiler default setting
-ffp-contract=fast.
* Added new options -mfsrra and -mfsca to allow the compiler using
the fsrra and fsca instructions on targets other than SH4A (where
they are already enabled by default).
* Added support for the __builtin_bswap32 built-in function. It is
now expanded as a sequence of swap.b and swap.w instructions
instead of a library function call.
* The behavior of the -mieee option has been fixed and the negative
form -mno-ieee has been added to control the IEEE conformance of
floating point comparisons. By default -mieee is now enabled and
the option -ffinite-math-only implicitly sets -mno-ieee.
* Added support for the built-in functions __builtin_thread_pointer
and __builtin_set_thread_pointer. This assumes that GBR is used to
hold the thread pointer of the current thread. Memory loads and
stores relative to the address returned by __builtin_thread_pointer
will now also utilize GBR based displacement address modes.
* The -mdiv= option for targets other than SHmedia has been fixed and
documented.
SPARC
* Added optimized instruction scheduling for Niagara4.
TILE-Gx
* Added support for the -mcmodel=MODEL command-line option. The
models supported are small and large.
V850
* This target now supports the E3V5 architecture via the use of the
new -mv850e3v5 command-line option. It also has experimental
support for the e3v5 LOOP instruction which can be enabled via the
new -mloop command-line option.
XStormy16
* This target now supports the -fstack-usage command-line option.
Operating Systems
Windows (Cygwin)
* Executables are now linked against shared libgcc by default. The
previous default was to link statically, which can still be done by
explicitly specifying -static or static-libgcc on the command line.
However it is strongly advised against, as it will cause problems
for any application that makes use of DLLs compiled by GCC. It
should be alright for a monolithic stand-alone application that
only links against the Windows DLLs, but offers little or no
benefit.
GCC 4.8.1
This is the [33]list of problem reports (PRs) from GCC's bug tracking
system that are known to be fixed in the 4.8.1 release. This list might
not be complete (that is, it is possible that some PRs that have been
fixed are not listed here).
The C++11 <chrono> std::chrono::system_clock and
std::chrono::steady_clock classes have changed ABI in GCC 4.8.1, they
both are now separate (never typedefs of each other), both use
std::chrono::nanoseconds resolution, on most GNU/Linux configurations
std::chrono::steady_clock is now finally monotonic, and both classes
are mangled differently than in the previous GCC releases.
std::chrono::system_clock::now() with std::chrono::microseconds resp.
std::chrono::seconds resolution is still exported for backwards
compatibility with default configured libstdc++. Note that libstdc++
configured with --enable-libstdcxx-time= used to be ABI incompatible
with default configured libstdc++ for those two classes and no ABI
compatibility can be offered for those configurations, so any C++11
code that uses those classes and has been compiled and linked against
libstdc++ configured with the non-default --enable-libstdcxx-time=
configuration option needs to be recompiled.
GCC 4.8.2
This is the [34]list of problem reports (PRs) from GCC's bug tracking
system that are known to be fixed in the 4.8.2 release. This list might
not be complete (that is, it is possible that some PRs that have been
fixed are not listed here).
GCC 4.8.3
This is the [35]list of problem reports (PRs) from GCC's bug tracking
system that are known to be fixed in the 4.8.3 release. This list might
not be complete (that is, it is possible that some PRs that have been
fixed are not listed here).
Support for the new powerpc64le-linux platform has been added. It
defaults to generating code that conforms to the ELFV2 ABI.
For questions related to the use of GCC, please consult these web
pages and the [36]GCC manuals. If that fails, the
[37][email protected] mailing list might help. Comments on these
web pages and the development of GCC are welcome on our developer
list at [38][email protected]. All of [39]our lists have public
archives.
Copyright (C) [40]Free Software Foundation, Inc. Verbatim copying and
distribution of this entire article is permitted in any medium,
provided this notice is preserved.
These pages are [41]maintained by the GCC team. Last modified
2014-05-22[42].
References
1. http://gcc.gnu.org/wiki/cxx-conversion
2. ftp://gcc.gnu.org/pub/gcc/infrastructure/
3. http://www.nongnu.org/avr-libc/
4. http://gcc.gnu.org/PR54461
5. http://gcc.gnu.org/gcc-4.8/porting_to.html
6. https://code.google.com/p/address-sanitizer/
7. https://code.google.com/p/data-race-test/wiki/ThreadSanitizer
8. https://lkml.org/lkml/2006/11/28/239
9. http://gcc.gnu.org/gcc-4.8/cxx0x_status.html
10. http://gcc.gnu.org/gcc-4.8/cxx0x_status.html
11. http://gcc.gnu.org/gcc-4.8/cxx0x_status.html
12. http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3276.pdf
13. http://gcc.gnu.org/gcc-4.8/cxx0x_status.html
14. http://www.open-std.org/JTC1/SC22/WG21/docs/papers/2012/n3386.html
15. http://gcc.gnu.org/projects/cxx1y.html
16. http://gcc.gnu.org/onlinedocs/libstdc++/manual/status.html#status.iso.2011
17. http://gcc.gnu.org/onlinedocs/gfortran/BACKTRACE.html
18. http://gcc.gnu.org/onlinedocs/gfortran/Error-and-Warning-Options.html
19. http://gcc.gnu.org/onlinedocs/gfortran/Error-and-Warning-Options.html
20. http://gcc.gnu.org/onlinedocs/gfortran/Code-Gen-Options.html
21. http://gcc.gnu.org/onlinedocs/gfortran/Error-and-Warning-Options.html
22. http://gcc.gnu.org/onlinedocs/gfortran/Error-and-Warning-Options.html
23. http://gcc.gnu.org/onlinedocs/gfortran/TMPDIR.html
24. http://gcc.gnu.org/wiki/Fortran2003Status
25. http://gcc.gnu.org/wiki/TS29113Status
26. http://gcc.gnu.org/viewcvs/trunk/libgfortran/libgfortran.h?content-type=text%2Fplain&view=co
27. http://chasm-interop.sourceforge.net/
28. http://gcc.gnu.org/wiki/avr-gcc#Fixed-Point_Support
29. http://gcc.gnu.org/onlinedocs/gcc/Fixed-Point.html
30. http://gcc.gnu.org/onlinedocs/gcc/X86-Built-in-Functions.html#X86-Built-in-Functions
31. http://gcc.gnu.org/onlinedocs/gcc/X86-Built-in-Functions.html#X86-Built-in-Functions
32. http://gcc.gnu.org/wiki/FunctionMultiVersioning
33. http://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.8.1
34. http://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.8.2
35. http://gcc.gnu.org/bugzilla/buglist.cgi?bug_status=RESOLVED&resolution=FIXED&target_milestone=4.8.3
36. http://gcc.gnu.org/onlinedocs/
37. mailto:[email protected]
38. mailto:[email protected]
39. http://gcc.gnu.org/lists.html
40. http://www.fsf.org/
41. http://gcc.gnu.org/about.html
42. http://validator.w3.org/check/referer
======================================================================
http://gcc.gnu.org/gcc-4.7/index.html
GCC 4.7 Release Series
April 11, 2013
The [1]GNU project and the GCC developers are pleased to announce the
release of GCC 4.7.3.
This release is a bug-fix release, containing fixes for regressions in
GCC 4.7.2 relative to previous releases of GCC.
Release History
GCC 4.7.3
April 11, 2013 ([2]changes, [3]documentation)
GCC 4.7.2
September 20, 2012 ([4]changes, [5]documentation)
GCC 4.7.1
June 14, 2012 ([6]changes, [7]documentation)
GCC 4.7.0
March 22, 2012 ([8]changes, [9]documentation)
References and Acknowledgements
GCC used to stand for the GNU C Compiler, but since the compiler
supports several other languages aside from C, it now stands for the
GNU Compiler Collection.
A list of [10]successful builds is updated as new information becomes
available.
The GCC developers would like to thank the numerous people that have
contributed new features, improvements, bug fixes, and other changes as
well as test results to GCC. This [11]amazing group of volunteers is
what makes GCC successful.
For additional information about GCC please refer to the [12]GCC
project web site or contact the [13]GCC development mailing list.
To obtain GCC please use [14]our mirror sites or [15]our SVN server.
For questions related to the use of GCC, please consult these web
pages and the [16]GCC manuals. If that fails, the
[17][email protected] mailing list might help. Comments on these
web pages and the development of GCC are welcome on our developer
list at [18][email protected]. All of [19]our lists have public
archives.
Copyright (C) [20]Free Software Foundation, Inc. Verbatim copying and
distribution of this entire article is permitted in any medium,
provided this notice is preserved.
These pages are [21]maintained by the GCC team. Last modified
2013-04-11[22].
References
1. http://www.gnu.org/
2. http://gcc.gnu.org/gcc-4.7/changes.html
3. http://gcc.gnu.org/onlinedocs/4.7.3/
4. http://gcc.gnu.org/gcc-4.7/changes.html
5. http://gcc.gnu.org/onlinedocs/4.7.2/
6. http://gcc.gnu.org/gcc-4.7/changes.html
7. http://gcc.gnu.org/onlinedocs/4.7.1/
8. http://gcc.gnu.org/gcc-4.7/changes.html
9. http://gcc.gnu.org/onlinedocs/4.7.0/
10. http://gcc.gnu.org/gcc-4.7/buildstat.html
11. http://gcc.gnu.org/onlinedocs/gcc/Contributors.html
12. http://gcc.gnu.org/index.html
13. mailto:[email protected]
14. http://gcc.gnu.org/mirrors.html
15. http://gcc.gnu.org/svn.html
16. http://gcc.gnu.org/onlinedocs/
17. mailto:[email protected]
18. mailto:[email protected]
19. http://gcc.gnu.org/lists.html
20. http://www.fsf.org/
21. http://gcc.gnu.org/about.html
22. http://validator.w3.org/check/referer
======================================================================
http://gcc.gnu.org/gcc-4.7/changes.html
GCC 4.7 Release Series
Changes, New Features, and Fixes
Caveats
* The -fconserve-space flag has been deprecated. The flag had no
effect for most targets: only targets without a global .bss section
and without support for switchable sections. Furthermore, the flag
only had an effect for G++, where it could result in wrong
semantics (please refer to the GCC manual for further details). The
flag will be removed in GCC 4.8
* Support for a number of older systems and recently unmaintained or
untested target ports of GCC has been declared obsolete in GCC 4.7.
Unless there is activity to revive them, the next release of GCC
will have their sources permanently removed.
All GCC ports for the following processor architectures have been
declared obsolete:
+ picoChip (picochip-*)
The following ports for individual systems on particular
architectures have been obsoleted:
+ IRIX 6.5 (mips-sgi-irix6.5)
+ MIPS OpenBSD (mips*-*-openbsd*)
+ Solaris 8 (*-*-solaris2.8). Details can be found in the
[1]announcement.
+ Tru64 UNIX V5.1 (alpha*-dec-osf5.1*)
* On ARM, when compiling for ARMv6 (but not ARMv6-M), ARMv7-A,
ARMv7-R, or ARMv7-M, the new option -munaligned-access is active by
default, which for some sources generates code that accesses memory
on unaligned addresses. This requires the kernel of those systems
to enable such accesses (controlled by CP15 register c1, refer to
ARM documentation). Alternatively, or for compatibility with
kernels where unaligned accesses are not supported, all code has to
be compiled with -mno-unaligned-access. Upstream Linux kernel
releases have automatically and unconditionally supported unaligned
accesses as emitted by GCC due to this option being active since
version 2.6.28.
* Support on ARM for the legacy floating-point accelerator (FPA) and
the mixed-endian floating-point format that it used has been
obsoleted. The ports that still use this format have been obsoleted
as well. Many legacy ARM ports already provide an alternative that
uses the VFP floating-point format. The obsolete ports will be
deleted in the next release.
The obsolete ports with alternatives are:
+ arm*-*-rtems (use arm*-*-rtemseabi)
+ arm*-*-linux-gnu (use arm*-*-linux-gnueabi)
+ arm*-*-elf (use arm*-*-eabi)
+ arm*-*-uclinux* (use arm*-*-uclinux*eabi)
Note, however, that these alternatives are not binary compatible
with their legacy counterparts (although some can support running
legacy applications).
The obsolete ports that currently lack a modern alternative are:
+ arm*-*-ecos-elf
+ arm*-*-freebsd
+ arm*-wince-pe*
New ports that support more recent versions of the architecture are
welcome.
* Support for the Maverick co-processor on ARM has been obsoleted.
Code to support it will be deleted in the next release.
* Support has been removed for Unix International threads on Solaris
2, so the --enable-threads=solaris configure option and the
-threads compiler option don't work any longer.
* Support has been removed for the Solaris BSD Compatibility Package,
which lives in /usr/ucbinclude and /usr/ucblib. It has been removed
from Solaris 11, and was only intended as a migration aid from
SunOS 4 to SunOS 5. The -compat-bsd compiler option is not
recognized any longer.
* The AVR port's libgcc has been improved and its multilib structure
has been enhanced. As a result, all objects contributing to an
application must either be compiled with GCC versions up to 4.6.x
or with GCC versions 4.7.1 or later. If the compiler is used with
AVR Libc, you need a version that supports the new layout, i.e.
implements [2]#35407.
* The AVR port's -mshort-calls command-line option has been