initial import of GCC 10.3.0. main changes include:

caveats:
- ABI issue between c++14 and c++17 fixed
- profile mode is removed from libstdc++
- -fno-common is now the default

new features:
- new flags -fallocation-dce, -fprofile-partial-training,
-fprofile-reproducible, -fprofile-prefix-path, and -fanalyzer
- many new compile and link time optimisations
- enhanced drive optimisations
- openacc 2.6 support
- openmp 5.0 features
- new warnings: -Wstring-compare and -Wzero-length-bounds
- extended warnings: -Warray-bounds, -Wformat-overflow,
-Wrestrict, -Wreturn-local-addr, -Wstringop-overflow,
-Warith-conversion, -Wmismatched-tags, and -Wredundant-tags
- some likely C2X features implemented
- more C++20 implemented
- many new arm & intel CPUs known

hundreds of reported bugs are fixed. full list of changes
can be found at:

https://gcc.gnu.org/gcc-10/changes.html

import GCC 7.4.0. main changes include:

The non-standard C++0x type traits has_trivial_default_constructor,
has_trivial_copy_constructor and has_trivial_copy_assign have been
removed.

On ARM targets (arm*-*-*), a bug introduced in GCC 5 that affects
conformance to the procedure call standard (AAPCS) has been fixed.

Many optimiser improvements

DWARF-5 support.

Many new and enhanced warnings.

Warnings about format strings now underline the pertinent part of
the string, and can offer suggested fixes.

Several new warnings related to buffer overflows and buffer
truncation.

New __builtin_add_overflow_p, __builtin_sub_overflow_p,
__builtin_mul_overflow_p built-ins added that test for overflow.

The C++ front end has experimental support for all of the current
C++17 draft.

The -fverbose-asm option has been expanded to prints comments
showing the source lines that correspond to the assembly.

The gcc and g++ driver programs will now provide suggestions for
misspelled arguments to command-line options.


AArch64 specific:

GCC has been updated to the latest revision of the procedure call
standard (AAPCS64) to provide support for parameter passing when
data types have been over-aligned.

The ARMv8.2-A and ARMv8.3-A architecture are now supported.

ARM specific:

Support for the ARMv5 and ARMv5E architectures has been
deprecated (which have no known implementations).

A new command-line option -mpure-code has been added. It does not
allow constant data to be placed in code sections.

x86 specific:

Support for the AVX-512 4FMAPS, 4VNNIW, VPOPCNTDQ and Software
Guard Extensions (SGX) ISA extensions has been added.

PPC specific:

GCC now diagnoses inline assembly that clobbers register r2.

RISC-V specific:

Support for the RISC-V instruction set has been added.

SH specific:

Support for SH5/SH64 has been removed.

Support for SH2A has been enhanced.

branches: 1.1.1.1.2; 1.1.1.1.4;
import GCC 6.4.0. see this url for details which are too large to
include here:

http://gcc.gnu.org/gcc-6/changes.html

the main visible changes appear to be:

- The default mode for C++ is now -std=gnu++14 instead of -std=gnu++98.
- The C and C++ compilers now support attributes on enumerators.
- Diagnostics can now contain "fix-it hints"
- more warnings (some added to -Wall)

import GCC 7.4.0. main changes include:

The non-standard C++0x type traits has_trivial_default_constructor,
has_trivial_copy_constructor and has_trivial_copy_assign have been
removed.

On ARM targets (arm*-*-*), a bug introduced in GCC 5 that affects
conformance to the procedure call standard (AAPCS) has been fixed.

Many optimiser improvements

DWARF-5 support.

Many new and enhanced warnings.

Warnings about format strings now underline the pertinent part of
the string, and can offer suggested fixes.

Several new warnings related to buffer overflows and buffer
truncation.

New __builtin_add_overflow_p, __builtin_sub_overflow_p,
__builtin_mul_overflow_p built-ins added that test for overflow.

The C++ front end has experimental support for all of the current
C++17 draft.

The -fverbose-asm option has been expanded to prints comments
showing the source lines that correspond to the assembly.

The gcc and g++ driver programs will now provide suggestions for
misspelled arguments to command-line options.


AArch64 specific:

GCC has been updated to the latest revision of the procedure call
standard (AAPCS64) to provide support for parameter passing when
data types have been over-aligned.

The ARMv8.2-A and ARMv8.3-A architecture are now supported.

ARM specific:

Support for the ARMv5 and ARMv5E architectures has been
deprecated (which have no known implementations).

A new command-line option -mpure-code has been added. It does not
allow constant data to be placed in code sections.

x86 specific:

Support for the AVX-512 4FMAPS, 4VNNIW, VPOPCNTDQ and Software
Guard Extensions (SGX) ISA extensions has been added.

PPC specific:

GCC now diagnoses inline assembly that clobbers register r2.

RISC-V specific:

Support for the RISC-V instruction set has been added.

SH specific:

Support for SH5/SH64 has been removed.

Support for SH2A has been enhanced.

branches: 1.1.1.1.2;
import GCC 6.4.0. see this url for details which are too large to
include here:

http://gcc.gnu.org/gcc-6/changes.html

the main visible changes appear to be:

- The default mode for C++ is now -std=gnu++14 instead of -std=gnu++98.
- The C and C++ compilers now support attributes on enumerators.
- Diagnostics can now contain "fix-it hints"
- more warnings (some added to -Wall)