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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-9/index.html
GCC 9 Release Series
Mar 12, 2020
The [1]GNU project and the GCC developers are pleased to announce the
release of GCC 9.3.
This release is a bug-fix release, containing fixes for regressions in
GCC 9.2 relative to previous releases of GCC.
Release History
GCC 9.3
Mar 12, 2020 ([2]changes, [3]documentation)
GCC 9.2
Aug 12, 2019 ([4]changes, [5]documentation)
GCC 9.1
May 3, 2019 ([6]changes, [7]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 [8]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 [9]amazing group of volunteers is
what makes GCC successful.
For additional information about GCC please refer to the [10]GCC
project web site or contact the [11]GCC development mailing list.
To obtain GCC please use [12]our mirror sites or [13]our version
control system.
For questions related to the use of GCC, please consult these web
pages and the [14]GCC manuals. If that fails, the
[15]gcc-help@gcc.gnu.org mailing list might help. Comments on these
web pages and the development of GCC are welcome on our developer
list at [16]gcc@gcc.gnu.org. All of [17]our lists have public
archives.
Copyright (C) [18]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 [19]maintained by the GCC team. Last modified
2020-03-12[20].
References
1. http://www.gnu.org/
2. http://gcc.gnu.org/gcc-9/changes.html
3. http://gcc.gnu.org/onlinedocs/9.3.0/
4. http://gcc.gnu.org/gcc-9/changes.html
5. http://gcc.gnu.org/onlinedocs/9.2.0/
6. http://gcc.gnu.org/gcc-9/changes.html
7. http://gcc.gnu.org/onlinedocs/9.1.0/
8. http://gcc.gnu.org/gcc-9/buildstat.html
9. http://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Contributors.html
10. http://gcc.gnu.org/index.html
11. mailto:gcc@gcc.gnu.org
12. http://gcc.gnu.org/mirrors.html
13. http://gcc.gnu.org/git.html
14. https://gcc.gnu.org/onlinedocs/
15. mailto:gcc-help@gcc.gnu.org
16. mailto:gcc@gcc.gnu.org
17. https://gcc.gnu.org/lists.html
18. https://www.fsf.org/
19. https://gcc.gnu.org/about.html
20. http://validator.w3.org/check/referer
======================================================================
http://gcc.gnu.org/gcc-9/changes.html
GCC 9 Release Series
Changes, New Features, and Fixes
This page is a "brief" summary of some of the huge number of
improvements in GCC 9. You may also want to check out our [1]Porting to
GCC 9 page and the [2]full GCC documentation.
Caveats
* On Arm targets (arm*-*-*), [3]a bug in the implementation of the
procedure call standard (AAPCS) in the GCC 6, 7 and 8 releases has
been fixed: a structure containing a bit-field based on a 64-bit
integral type and where no other element in a structure required
64-bit alignment could be passed incorrectly to functions. This is
an ABI change. If the option -Wpsabi is enabled (on by default) the
compiler will emit a diagnostic note for code that might be
affected.
* Support for a number of older systems and recently unmaintained or
untested target ports of GCC has been declared obsolete in GCC 9.
Unless there is activity to revive them, the next release of GCC
will have their sources permanently removed.
The following ports for individual systems on particular
architectures have been obsoleted:
+ Solaris 10 (*-*-solaris2.10). Details can be found in the
[4]announcement.
+ Cell Broadband Engine SPU (spu*-*-*). Details can be found in
the [5]announcement.
* A change to the C++ std::rotate algorithm in GCC 9.1.0 can cause
ABI incompatibilities with object files compiled with other
versions of GCC. If the std::rotate algorithm is called with an
empty range then it might cause a divide-by-zero error (as a SIGFPE
signal) and crash. The change has been reverted for GCC 9.2.0 and
future releases. For more details see [6]Bug 90920. The problem can
be avoided by recompiling any objects that might call std::rotate
with an empty range, so that the GCC 9.1.0 definition of
std::rotate is not used.
* The automatic template instantiation at link time ([7]-frepo) has
been deprecated and will be removed in a future release.
* The --with-default-libstdcxx-abi=gcc4-compatible configure option
is broken in the 9.1 and 9.2 releases, producing a shared library
with missing symbols (see [8]Bug 90361). As a workaround, configure
without that option and build GCC as normal, then edit the
installed <bits/c++config.h> headers to define the
_GLIBCXX_USE_CXX11_ABI macro to 0.
General Improvements
The following GCC command line options have been introduced or
improved.
* All command line options that take a byte-size argument accept
64-bit integers as well as standard SI and IEC suffixes such as kb
and KiB, MB and MiB, or GB and GiB denoting the corresponding
multiples of bytes. See [9]Invoking GCC for more.
* A new option,
[10]-flive-patching=[inline-only-static|inline-clone], has been
introduced to provide a safe compilation for live-patching. At the
same time, provides multiple-level control on the enabled IPA
optimizations. See the user guide for more details about the
option.
* A new option, --completion, has been added to provide more fine
option completion in a shell. It is intended to be used by
Bash-completion.
* GCC's diagnostics now print source code with a left margin showing
line numbers, configurable with
[11]-fno-diagnostics-show-line-numbers.
GCC's diagnostics can also now label regions of the source code to
show pertinent information, such as the types within an expression.
$ g++ t.cc
t.cc: In function 'int test(const shape&, const shape&)':
t.cc:15:4: error: no match for 'operator+' (operand types are 'boxed_value<doubl
e>' and 'boxed_value<double>')
14 | return (width(s1) * height(s1)
| ~~~~~~~~~~~~~~~~~~~~~~
| |
| boxed_value<[...]>
15 | + width(s2) * height(s2));
| ^ ~~~~~~~~~~~~~~~~~~~~~~
| |
| boxed_value<[...]>
These labels can be disabled via [12]-fno-diagnostics-show-labels.
* A new option [13]-fdiagnostics-format=json has been introduced for
emitting diagnostics in a machine-readable format.
* The alignment-related options [14]-falign-functions,
[15]-falign-labels, [16]-falign-loops, and [17]-falign-jumps
received support for a secondary alignment (e.g.
-falign-loops=n:m:n2:m2).
* New pair of profiling options ([18]-fprofile-filter-files and
[19]-fprofile-exclude-files) has been added. The options help to
filter which source files are instrumented.
* AddressSanitizer generates more compact redzones for automatic
variables. That helps to reduce memory footprint of a sanitized
binary.
* Numerous improvements have been made to the output of
[20]-fopt-info.
Messages are now prefixed with optimized, missed, or note, rather
than the old behavior of all being prefixed with note.
The output from -fopt-info can now contain information on inlining
decisions:
$ g++ -c inline.cc -O2 -fopt-info-inline-all
inline.cc:24:11: note: Considering inline candidate void foreach(T, T, void (*)(
E)) [with T = char**; E = char*]/2.
inline.cc:24:11: optimized: Inlining void foreach(T, T, void (*)(E)) [with T =
char**; E = char*]/2 into int main(int, char**)/1.
inline.cc:19:12: missed: not inlinable: void inline_me(char*)/0 -> int std::pu
ts(const char*)/3, function body not available
inline.cc:13:8: optimized: Inlined void inline_me(char*)/4 into int main(int, c
har**)/1 which now has time 127.363637 and size 11, net change of +0.
Unit growth for small function inlining: 16->16 (0%)
Inlined 2 calls, eliminated 1 functions
The output from the vectorizer has been rationalized so that failed
attempts to vectorize a loop are displayed in the form
[LOOP-LOCATION]: couldn't vectorize this loop
[PROBLEM-LOCATION]: because of [REASON]
rather than an exhaustive log of all decisions made by the
vectorizer. For example:
$ gcc -c v.c -O3 -fopt-info-all-vec
v.c:7:3: missed: couldn't vectorize loop
v.c:10:7: missed: statement clobbers memory: __asm__ __volatile__("" : : : "me
mory");
v.c:3:6: note: vectorized 0 loops in function.
v.c:10:7: missed: statement clobbers memory: __asm__ __volatile__("" : : : "me
mory");
The old behavior can be obtained via a new -internals suboption of
-fopt-info.
* A new option, [21]-fsave-optimization-record has been added, which
writes a SRCFILE.opt-record.json.gz file describing the
optimization decisions made by GCC. This is similar to the output
of -fopt-info, but with additional metadata such as the inlining
chain, and profile information (if available).
* Inter-procedural propagation of stack alignment can now be
controlled by [22]-fipa-stack-alignment.
* Propagation of addressability, readonly and writeonly flags on
static variables can now be controlled by
[23]-fipa-reference-addressable.
The following built-in functions have been introduced.
* [24]__builtin_expect_with_probability to provide branch prediction
probability hints to the optimizer.
* [25]__builtin_has_attribute determines whether a function, type, or
variable has been declared with some attribute.
* [26]__builtin_speculation_safe_value can be used to help mitigate
against unsafe speculative execution.
The following attributes have been introduced.
* The [27]copy function attribute has been added. The attribute can
also be applied to type definitions and to variable declarations.
A large number of improvements to code generation have been made,
including but not limited to the following.
* Switch expansion has been improved by using a different strategy
(jump table, bit test, decision tree) for a subset of switch cases.
* A linear function expression defined as a switch statement can be
transformed by [28]-ftree-switch-conversion. For example:
int
foo (int how)
{
switch (how) {
case 2: how = 205; break;
case 3: how = 305; break;
case 4: how = 405; break;
case 5: how = 505; break;
case 6: how = 605; break;
}
return how;
}
can be transformed into 100 * how + 5 (for values defined in the
switch statement).
* Inter-procedural optimization improvements:
+ Inliner defaults was tuned to better suits modern C++
codebases especially when built with link time optimizations.
New parameters max-inline-insns-small, max-inline-insns-size,
uninlined-function-insns, uninlined-function-time,
uninlined-thunk-insns, and uninlined-thunk-time were added.
+ Hot/cold partitioning is now more precise and aggressive.
+ Improved scalability for very large translation units
(especially when link-time optimizing large programs).
* Profile driven optimization improvements:
+ [29]-fprofile-use now enables [30]-fversion-loops-for-strides,
[31]-floop-interchange, [32]-floop-unroll-and-jam,
[33]-ftree-loop-distribution.
+ Streaming of counter histograms was removed. This reduces the
size of profile files. Histogram is computed on the fly with
link-time optimization. Parameter hot-bb-count-ws-permille was
reduced from 999 to 990 to account for more precise
histograms.
* Link-time optimization improvements:
+ Types are now simplified prior streaming resulting in
significant reductions of the LTO object files, link-time
memory use, and improvements of link-time parallelism.
+ Default number of partitions (--param lto-partitions) was
increased from 32 to 128 enabling effective use of CPUs with
more than 32 hyperthreads. --param
lto-max-streaming-parallelism can now be used to control
number of streaming processes.
+ Warnings on C++ One Decl Rule violations (-Wodr) are now more
informative and produce fewer redundant results.
Overall compile time of Firefox 66 and LibreOffice 6.2.3 on an
8-core machine was reduced by about 5% compared to GCC 8.3, and the
size of LTO object files by 7%. LTO link-time improves by 11% on an
8-core machine and scales significantly better for more parallel
build environments. The serial stage of the link-time optimization
is 28% faster consuming 20% less memory. The parallel stage now
scales to up to 128 partitions rather than 32 and reduces memory
use for every worker by 30%.
The following improvements to the gcov command-line utility have been
made.
* The gcov tool received a new option [34]--use-hotness-colors (-q)
that can provide perf-like coloring of hot functions.
* The gcov tool has changed its intermediate format to a new JSON
format.
New Languages and Language specific improvements
[35]OpenACC support in C, C++, and Fortran continues to be maintained
and improved. Most of the OpenACC 2.5 specification is implemented. See
the [36]implementation status section on the OpenACC wiki page for
further information.
C family
* Version 5.0 of the [37]OpenMP specification is now partially
supported in the C and C++ compilers. For details which features of
OpenMP 5.0 are and which are not supported in the GCC 9 release see
[38]this mail.
* New extensions:
+ [39]__builtin_convertvector built-in for vector conversions
has been added.
* New warnings:
+ [40]-Waddress-of-packed-member, enabled by default, warns
about an unaligned pointer value from the address of a packed
member of a struct or union.
* Enhancements to existing warnings:
+ [41]-Warray-bounds detects more instances of out-of-bounds
indices.
+ [42]-Wattribute-alias also detects attribute mismatches
between alias declarations and their targets, in addition to
mismatches between their types.
+ [43]-Wformat-overflow and [44]-Wformat-truncation have been
extended to all formatted input/output functions (where
applicable) and enhanced to detect a subset of instances of
reading past the end of unterminated constant character arrays
in %s directives.
+ [45]-Wmissing-attributes detects instances of missing function
attributes on declarations of aliases and weak references.
+ [46]-Wstringop-truncation also detects a subset of instances
of reading past the end of unterminated constant character
arrays,
* If a macro is used with the wrong argument count, the C and C++
front ends now show the definition of that macro via a note.
* The spelling corrector now considers transposed letters, and the
threshold for similarity has been tightened, to avoid nonsensical
suggestions.
C
* There is now experimental support for -std=c2x, to select support
for the upcoming C2X revision of the ISO C standard. This standard
is in the early stages of development and the only feature
supported in GCC 9 is _Static_assert with a single argument
(support for _Static_assert with two arguments was added in C11 and
GCC 4.6). There are also new options -std=gnu2x, for C2X with GNU
extensions, and -Wc11-c2x-compat, to warn for uses of features
added in C2X (such warnings are also enabled by use of -Wpedantic
if not using -std=c2x or -std=gnu2x).
* New warnings:
+ [47]-Wabsolute-value warns for calls to standard functions
that compute the absolute value of an argument when a more
appropriate standard function is available. For example,
calling abs(3.14) triggers the warning because the appropriate
function to call to compute the absolute value of a double
argument is fabs. The option also triggers warnings when the
argument in a call to such a function has an unsigned type.
This warning can be suppressed with an explicit type cast and
it is also enabled by -Wextra.
C++
* New warnings:
+ [48]-Wdeprecated-copy, implied by -Wextra, warns about the
C++11 deprecation of implicitly declared copy constructor and
assignment operator if one of them is user-provided.
-Wdeprecated-copy-dtor also warns if the destructor is
user-provided, as specified in C++11.
+ [49]-Winit-list-lifetime, on by default, warns about uses of
std::initializer_list that are likely to result in a dangling
pointer, such as returning or assigning from a temporary list.
+ [50]-Wredundant-move, implied by -Wextra, warns about
redundant calls to std::move.
+ [51]-Wpessimizing-move, implied by -Wall, warns when a call to
std::move prevents copy elision.
+ [52]-Wclass-conversion, on by default, warns when a conversion
function will never be called due to the type it converts to.
* The C++ front end has experimental support for some of the upcoming
C++2a draft features with the -std=c++2a or -std=gnu++2a flags,
including range-based for statements with initializer, default
constructible and assignable stateless lambdas, lambdas in
unevaluated contexts, language support for empty data members,
allowing pack expansion in lambda init-capture, likely and unlikely
attributes, class types in non-type template parameters, allowing
virtual function calls in constant expressions, explicit(bool),
std::is_constant_evaluated, nested inline namespaces, etc. For a
full list of new features, see [53]the C++ status page.
* The C++ front end now preserves source locations for literals,
id-expression, and mem-initializer for longer. For example it is
now able to pin-point the pertinent locations for bad
initializations such as these
$ g++ -c bad-inits.cc
bad-inits.cc:10:14: error: cannot convert 'json' to 'int' in initialization
10 | { 3, json::object },
| ~~~~~~^~~~~~
| |
| json
bad-inits.cc:14:31: error: initializer-string for array of chars is too long [-f
permissive]
14 | char buffers[3][5] = { "red", "green", "blue" };
| ^~~~~~~
bad-inits.cc: In constructor 'X::X()':
bad-inits.cc:17:13: error: invalid conversion from 'int' to 'void*' [-fpermissiv
e]
17 | X() : one(42), two(42), three(42)
| ^~
| |
| int
rather than emitting the error at the final closing parenthesis or
brace.
* Error-reporting of overload resolution has been special-cased to
make the case of a single failed candidate easier to read. For
example:
$ g++ param-type-mismatch.cc
param-type-mismatch.cc: In function 'int test(int, const char*, float)':
param-type-mismatch.cc:8:32: error: cannot convert 'const char*' to 'const char*
*'
8 | return foo::member_1 (first, second, third);
| ^~~~~~
| |
| const char*
param-type-mismatch.cc:3:46: note: initializing argument 2 of 'static int foo:
:member_1(int, const char**, float)'
3 | static int member_1 (int one, const char **two, float three);
| ~~~~~~~~~~~~~^~~
highlights both the problematic argument, and the parameter that it
can't be converted to.
* Diagnostics involving binary operators now use color to distinguish
the two operands, and label them separately (as per the example of
source labelling above).
* Diagnostics involving function calls now highlight the pertinent
parameter of the declaration in more places.
$ g++ bad-conversion.cc
bad-conversion.cc: In function 'void caller()':
bad-conversion.cc:9:14: error: cannot convert 'bool' to 'void*'
9 | callee (0, false, 2);
| ^~~~~
| |
| bool
bad-conversion.cc:3:19: note: initializing argument 2 of 'void callee(int, voi
d*, int)'
3 | void callee (int, void *, int)
| ^~~~~~
* The C++ front end's implementation of [54]-Wformat now shows
precise locations within string literals, and underlines the
pertinent arguments at bogus call sites (the C front end has been
doing this since GCC 7). For example:
$ g++ -c bad-printf.cc -Wall
bad-printf.cc: In function 'void print_field(const char*, float, long int, long
int)':
bad-printf.cc:6:17: warning: field width specifier '*' expects argument of type
'int', but argument 3 has type 'long int' [-Wformat=]
6 | printf ("%s: %*ld ", fieldname, column - width, value);
| ~^~~ ~~~~~~~~~~~~~~
| | |
| int long int
bad-printf.cc:6:19: warning: format '%ld' expects argument of type 'long int', b
ut argument 4 has type 'double' [-Wformat=]
6 | printf ("%s: %*ld ", fieldname, column - width, value);
| ~~~^ ~~~~~
| | |
| long int double
| %*f
* The C++ front end has gained new fix-it hints for forgetting the
return *this; needed by various C++ operators:
$ g++ -c operator.cc
operator.cc: In member function 'boxed_ptr& boxed_ptr::operator=(const boxed_ptr
&)':
operator.cc:7:3: warning: no return statement in function returning non-void [-W
return-type]
6 | m_ptr = other.m_ptr;
+++ |+ return *this;
7 | }
| ^
for when the compiler needs a typename:
$ g++ -c template.cc
template.cc:3:3: error: need 'typename' before 'Traits::type' because 'Traits' i
s a dependent scope
3 | Traits::type type;
| ^~~~~~
| typename
when trying to use an accessor member as if it were a data member:
$ g++ -c fncall.cc
fncall.cc: In function 'void hangman(const mystring&)':
fncall.cc:12:11: error: invalid use of member function 'int mystring::get_length
() const' (did you forget the '()' ?)
12 | if (str.get_length > 0)
| ~~~~^~~~~~~~~~
| ()
for C++11's scoped enums:
$ g++ -c enums.cc
enums.cc: In function 'void json::test(const json::value&)':
enums.cc:12:26: error: 'STRING' was not declared in this scope; did you mean 'js
on::kind::STRING'?
12 | if (v.get_kind () == STRING)
| ^~~~~~
| json::kind::STRING
enums.cc:3:44: note: 'json::kind::STRING' declared here
3 | enum class kind { OBJECT, ARRAY, NUMBER, STRING, TRUE, FALSE, NULL_ };
| ^~~~~~
and a tweak to integrate the suggestions about misspelled members
with that for accessors:
$ g++ -c accessor-fixit.cc
accessor-fixit.cc: In function 'int test(t*)':
accessor-fixit.cc:17:15: error: 'class t' has no member named 'ratio'; did you m
ean 'int t::m_ratio'? (accessible via 'int t::get_ratio() const')
17 | return ptr->ratio;
| ^~~~~
| get_ratio()
In addition, various diagnostics in the C++ front-end have been
streamlined by consolidating the suggestion into the initial error,
rather than emitting a follow-up note:
$ g++ typo.cc
typo.cc:5:13: error: 'BUFSIZE' was not declared in this scope; did you mean 'BUF
_SIZE'?
5 | uint8_t buf[BUFSIZE];
| ^~~~~~~
| BUF_SIZE
Runtime Library (libstdc++)
* Improved support for C++17, including:
+ The C++17 implementation is no longer experimental.
+ Parallel algorithms and <execution> (requires [55]Thread
Building Blocks 2018 or newer).
+ <memory_resource>.
+ Using the types and functions in <filesystem> does not require
linking with -lstdc++fs now.
* Improved experimental support for C++2a, including:
+ Type traits std::remove_cvref, std::unwrap_reference,
std::unwrap_decay_ref, std::is_nothrow_convertible, and
std::type_identity.
+ Headers <bit> and <version>.
+ Uniform container erasure (std::erase_if).
+ contains member of maps and sets.
+ String prefix and suffix checking (starts_with, ends_with).
+ Functions std::midpoint and std::lerp for interpolation.
+ std::bind_front.
+ std::visit<R>.
+ std::assume_aligned.
+ Uses-allocator construction utilities.
+ std::pmr::polymorphic_allocator<std::byte>.
+ Library support for char8_t type.
+ Destroying delete.
+ std::is_constant_evaluated() function.
* Support for opening file streams with wide character paths on
Windows
* Incomplete support for the C++17 Filesystem library and the
Filesystem TS on Windows.
* Incomplete, experimental support for the Networking TS.
D
* Support for the D programming language has been added to GCC,
implementing version 2.076 of the language and run-time library.
Fortran
* Asynchronous I/O is now fully supported. The program needs to be
linked against the pthreads library to use it, otherwise the I/O is
done synchronously. For systems which do not support POSIX
condition variables, such as AIX, all I/O is still done
synchronously.
* The BACK argument for MINLOC and MAXLOC has been implemented.
* The FINDLOC intrinsic function has been implemented.
* The IS_CONTIGUOUS intrinsic function has been implemented.
* Direct access to the real and imaginary parts of a complex variable
via c%re and c%im has been implemented.
* Type parameter inquiry via str%len and a%kind has been implemented.
* C descriptors and the ISO_Fortran_binding.h source file have been
implemented.
* The MAX and MIN intrinsics are no longer guaranteed to return any
particular value in case one of the arguments is a NaN. Note that
this conforms to the Fortran standard and to what other Fortran
compilers do. If there is a need to handle that case in some
specific way, one needs to explicitly check for NaN's before
calling MAX or MIN, e.g. by using the IEEE_IS_NAN function from the
intrinsic module IEEE_ARITHMETIC.
* A new command-line option [56]-fdec-include, set also by the
[57]-fdec option, has been added to increase compatibility with
legacy code. With this option, an INCLUDE directive is also parsed
as a statement, which allows the directive to be spread across
multiple source lines with line continuations.
* A new [58]BUILTIN directive, has been added. The purpose of the
directive is to provide an API between the GCC compiler and the GNU
C Library which would define vector implementations of math
routines.
Go
* GCC 9 provides a complete implementation of the Go 1.12.2 user
packages.
libgccjit
* The libgccjit API gained a new entry point:
[59]gcc_jit_context_add_driver_option.
New Targets and Target Specific Improvements
AArch64 & Arm
* Support has been added for the following processors (GCC
identifiers in parentheses):
+ Arm Cortex-A76 (cortex-a76).
+ Arm Cortex-A55/Cortex-A76 DynamIQ big.LITTLE
(cortex-a76.cortex-a55).
+ Arm Neoverse N1 (neoverse-n1).
The GCC identifiers can be used as arguments to the -mcpu or -mtune
options, for example: -mcpu=cortex-a76 or
-mtune=cortex-a76.cortex-a55 or as arguments to the equivalent
target attributes and pragmas.
* The Armv8.3-A complex number instructions are now supported via
intrinsics when the option -march=armv8.3-a or equivalent is
specified. For the half-precision floating-point variants of these
instructions use the architecture extension flag +fp16, e.g.
-march=armv8.3-a+fp16.
The intrinsics are defined by the ACLE specification.
* The Armv8.5-A architecture is now supported through the
-march=armv8.5-a option.
* The Armv8.5-A architecture also adds some security features that
are optional to all older architecture versions. These are now
supported and only affect the assembler.
+ Speculation Barrier instruction through the -march=armv8-a+sb
option.
+ Execution and Data Prediction Restriction instructions through
the -march=armv8-a+predres option.
+ Speculative Store Bypass Safe instruction through the
-march=armv8-a+ssbs option. This does not require a compiler
option for Arm and thus -march=armv8-a+ssbs is an
AArch64-specific option.
AArch64 specific
* Support has been added for the Arm Neoverse E1 processor
(-mcpu=neoverse-e1).
* The AArch64 port now has support for stack clash protection using
the [60]-fstack-clash-protection option. The probing interval/guard
size can be set by using --param
stack-clash-protection-guard-size=12|16. The value of this
parameter must be in bytes represented as a power of two. The two
supported values for this parameter are 12 (for a 4KiB size, 2^12)
and 16 (for a 64KiB size, 2^16). The default value is 16 (64Kb) and
can be changed at configure time using the flag
--with-stack-clash-protection-guard-size=12|16.
* The option -msign-return-address= has been deprecated. This has
been replaced by the new -mbranch-protection= option. This new
option can now be used to enable the return address signing as well
as the new Branch Target Identification feature of Armv8.5-A
architecture. For more information on the arguments accepted by
this option, please refer to [61]AArch64-Options.
* The following optional extensions to Armv8.5-A architecture are now
supported and only affect the assembler.
+ Random Number Generation instructions through the
-march=armv8.5-a+rng option.
+ Memory Tagging Extension through the -march=armv8.5-a+memtag
option.
Arm specific
* Support for the deprecated Armv2 and Armv3 architectures and their
variants has been removed. Their corresponding -march values and
the -mcpu options that used these architectures have been removed.
* Support for the Armv5 and Armv5E architectures (which have no known
implementations) has been removed. Note that Armv5T, Armv5TE and
Armv5TEJ architectures remain supported.
* Corrected FPU configurations for Cortex-R7 and Cortex-R8 when using
their respective -mcpu options.
AMD GCN
* A new back end targeting AMD GCN GPUs has been contributed to GCC.
The implementation is currently limited to compiling
single-threaded, stand-alone programs. Future versions will add
support for offloading multi-threaded kernels via OpenMP and
OpenACC. The following devices are supported (GCC identifiers in
parentheses):
+ Fiji (fiji).
+ Vega 10 (gfx900).
ARC
* LRA is now on by default for the ARC target. This can be controlled
by -mlra.
* Add support for frame code-density and branch-and-index
instructions.
C-SKY
* A new back end targeting C-SKY V2 processors has been contributed
to GCC.
IA-32/x86-64
* Support of Intel MPX (Memory Protection Extensions) has been
removed.
* New ISA extension support for Intel PTWRITE was added to GCC.
PTWRITE intrinsics are available via the -mptwrite compiler switch.
* GCC now supports the Intel CPU named Cascade Lake with AVX512
extensions through -march=cascadelake. The switch enables the
following ISA extensions: AVX512F, AVX512VL, AVX512CD, AVX512BW,
AVX512DQ, AVX512VNNI.
OpenRISC
* A new back end targeting OpenRISC processors has been contributed
to GCC.
S/390, System z, IBM z Systems
* Support for the arch13 architecture has been added. When using the
-march=arch13 option, the compiler will generate code making use of
the new instructions introduced with the vector enhancement
facility 2 and the miscellaneous instruction extension facility 2.
The -mtune=arch13 option enables arch13 specific instruction
scheduling without making use of new instructions.
* Builtins for the new vector instructions have been added and can be
enabled using the -mzvector option.
* Support for ESA architecture machines g5 and g6 is deprecated since
GCC 6.1.0 and has been removed now.
* When compiling with -march=z14 or higher GCC emits alignments hints
on the vector load/store instructions (8 or 16 byte).
* Functions now have a default alignment of 16 bytes. This helps with
branch prediction effects.
* -mfentry is now supported. As well as the mcount mechanism the
__fentry__ is called before the function prologue. However, since
just a single instruction is required to call __fentry__ the call
sequence imposes a smaller overhead than mcount (4 instructions).
The produced code is compatible only with newer glibc versions,
which provide the __fentry__ symbol and do not clobber r0 when
resolving lazily bound functions. -mfentry is only supported when
generating 64 bit code and does not work with nested C functions.
* The -mnop-mcount option can be used to emit NOP instructions
instead of an mcount or fentry call stub.
* With the -mrecord-mcount option a __mcount_loc section is generated
containing pointers to each profiling call stub. This is useful for
automatically patching in and out calls.
Operating Systems
Solaris
* g++ now unconditionally enables large file support when compiling
32-bit code.
* Support for the AddressSanitizer and UndefinedBehaviorSanitizer has
been merged from LLVM. For the moment, this only works for 32-bit
code on both SPARC and x86.
* An initial port of the D runtime library has been completed on
Solaris 11/x86. It requires the use of GNU as. Solaris 11/SPARC
support is still work-in-progress.
Windows
* A C++ Microsoft ABI bitfield layout bug, [62]PR87137 has been
fixed. A non-field declaration could cause the current bitfield
allocation unit to be completed, incorrectly placing a following
bitfield into a new allocation unit. The Microsoft ABI is selected
for:
+ Mingw targets
+ PowerPC, IA-32 or x86-64 targets when the -mms-bitfields
option is specified, or __attribute__((ms_struct)) is used
+ SuperH targets when the -mhitachi option is specified, or
__attribute__((renesas)) is used
Improvements for plugin authors
* GCC's diagnostic subsystem now has a way to logically group
together related diagnostics, auto_diagnostic_group. Such
diagnostics will be nested by the output of
[63]-fdiagnostics-format=json.
* GCC now has a set of [64]user experience guidelines for GCC, with
information and advice on implementing new diagnostics.
Other significant improvements
* GCC's internal "selftest" suite now runs for C++ as well as C (in
debug builds of the compiler).
GCC 9.1
This is the [65]list of problem reports (PRs) from GCC's bug tracking
system that are known to be fixed in the 9.1 release. This list might
not be complete (that is, it is possible that some PRs that have been
fixed are not listed here).
GCC 9.2
This is the [66]list of problem reports (PRs) from GCC's bug tracking
system that are known to be fixed in the 9.2 release. This list might
not be complete (that is, it is possible that some PRs that have been
fixed are not listed here).
GCC 9.3
This is the [67]list of problem reports (PRs) from GCC's bug tracking
system that are known to be fixed in the 9.3 release. This list might
not be complete (that is, it is possible that some PRs that have been
fixed are not listed here).
For questions related to the use of GCC, please consult these web
pages and the [68]GCC manuals. If that fails, the
[69]gcc-help@gcc.gnu.org mailing list might help. Comments on these
web pages and the development of GCC are welcome on our developer
list at [70]gcc@gcc.gnu.org. All of [71]our lists have public
archives.
Copyright (C) [72]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 [73]maintained by the GCC team. Last modified
2020-03-12[74].
References
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13. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Diagnostic-Message-Formatting-Options.html#index-fdiagnostics-format
14. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Optimize-Options.html#index-falign-functions
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16. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Optimize-Options.html#index-falign-loops
17. https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Optimize-Options.html#index-falign-jumps
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35. https://www.openacc.org/
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55. https://github.com/intel/tbb
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74. http://validator.w3.org/check/referer
======================================================================
http://gcc.gnu.org/gcc-8/index.html
GCC 8 Release Series
Mar 4, 2020
The [1]GNU project and the GCC developers are pleased to announce the
release of GCC 8.4.
This release is a bug-fix release, containing fixes for regressions in
GCC 8.3 relative to previous releases of GCC.
Release History
GCC 8.4
Mar 4, 2020 ([2]changes, [3]documentation)
GCC 8.3
Feb 22, 2019 ([4]changes, [5]documentation)
GCC 8.2
Jul 26, 2018 ([6]changes, [7]documentation)
GCC 8.1
May 2, 2018 ([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 version
control system.
For questions related to the use of GCC, please consult these web
pages and the [16]GCC manuals. If that fails, the
[17]gcc-help@gcc.gnu.org mailing list might help. Comments on these
web pages and the development of GCC are welcome on our developer
list at [18]gcc@gcc.gnu.org. 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
2020-03-04[22].
References
1. http://www.gnu.org/
2. http://gcc.gnu.org/gcc-8/changes.html
3. http://gcc.gnu.org/onlinedocs/8.4.0/
4. http://gcc.gnu.org/gcc-8/changes.html
5. http://gcc.gnu.org/onlinedocs/8.3.0/
6. http://gcc.gnu.org/gcc-8/changes.html
7. http://gcc.gnu.org/onlinedocs/8.2.0/
8. http://gcc.gnu.org/gcc-8/changes.html
9. http://gcc.gnu.org/onlinedocs/8.1.0/
10. http://gcc.gnu.org/gcc-8/buildstat.html
11. http://gcc.gnu.org/onlinedocs/gcc-8.1.0/gcc/Contributors.html
12. http://gcc.gnu.org/index.html
13. mailto:gcc@gcc.gnu.org
14. http://gcc.gnu.org/mirrors.html
15. http://gcc.gnu.org/git.html
16. https://gcc.gnu.org/onlinedocs/
17. mailto:gcc-help@gcc.gnu.org
18. mailto:gcc@gcc.gnu.org
19. https://gcc.gnu.org/lists.html
20. https://www.fsf.org/
21. https://gcc.gnu.org/about.html
22. http://validator.w3.org/check/referer
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http://gcc.gnu.org/gcc-8/changes.html
GCC 8 Release Series
Changes, New Features, and Fixes