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gcc/libstdc++-v3
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Jonathan Wakely 7f851c3341 libstdc++: Fix __numeric_traits_integer<__int20> [PR 97798] 
The expression used to calculate the maximum value for an integer type
assumes that the number of bits in the value representation is always
sizeof(T) * CHAR_BIT. This is not true for the __int20 type on msp430,
which has only 20 bits in the value representation but 32 bits in the
object representation. This causes an integer overflow in a constant
expression, which is ill-formed.

This problem was already solved by DJ for std::numeric_limits<__int20>
by generalizing the helper macros to use a specified number of bits
instead of assuming sizeof(T) * CHAR_BIT. Then the INT_N_n types can
specify the number of bits using the __GLIBCXX_BITSIZE_INT_N_n macros
that the compiler defines.

I'm using a slightly different approach here. I've replaced the helper
macros entirely, and just expanded the calculations in the initializers
for the static data members. By reordering the data members we can reuse
__is_signed and __digits in the other initializers. This removes the
repetition of expanding __glibcxx_signed(T) and __glibcxx_digits(T)
multiple times in each initializer.

The __is_integer_nonstrict trait now defines a new constant, __width,
which is sizeof(T) * CHAR_BIT by default (defined as an enumerator so
that no storage is needed for a static data member). By specializing
__is_integer_nonstrict for the INT_N types that have padding bits, we
can provide the correct width via the __GLIBCXX_BITSIZE_INT_N_n macros.

libstdc++-v3/ChangeLog:

	PR libstdc++/97798
	* include/ext/numeric_traits.h (__glibcxx_signed)
	(__glibcxx_digits, __glibcxx_min, __glibcxx_max): Remove
	macros.
	(__is_integer_nonstrict::__width): Define new constant.
	(__numeric_traits_integer): Define constants in terms of each
	other and __is_integer_nonstrict::__width, rather than the
	removed macros.
	(_GLIBCXX_INT_N_TRAITS): Macro to define explicit
	specializations for non-standard integer types.
2020-11-12 12:10:10 +00:00
..
config libstdc++: Avoid bad_alloc exceptions when changing locales 2020-11-10 20:33:29 +00:00
doc libstdc++: Document istreambuf_iterator base class change [PR 92285] 2020-11-04 12:46:52 +00:00
include libstdc++: Fix __numeric_traits_integer<__int20> [PR 97798] 2020-11-12 12:10:10 +00:00
libsupc++ libstdc++: Use 'inline' consistently in std::exception_ptr [PR 97729] 2020-11-09 14:28:38 +00:00
po libstdc++: Regenerate makefiles 2020-06-23 07:59:40 +01:00
python libstdc++: Fix compatibility support in unique_ptr pretty printer 2020-08-10 18:47:06 +01:00
scripts libstdc++: Pass CXXFLAGS to check_performance script 2020-10-09 14:01:55 +01:00
src libstdc++: Add remaining C++20 additions to <sstream> [P0408R7] 2020-11-10 19:22:47 +00:00
testsuite libstdc++: Assigning to a joinable std::jthread calls std::terminate 2020-11-11 11:13:31 +00:00
acinclude.m4 libstdc++: Exclude cygwin and mingw from linker relro support 2020-11-11 15:36:05 +00:00
aclocal.m4 Add `--with-toolexeclibdir=' configuration option 2020-01-24 11:24:25 +00:00
ChangeLog Daily bump. 2020-11-12 00:16:39 +00:00
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ChangeLog-2019 libstdc++: Fix whitespace in ChangeLog-2019 2020-01-09 21:31:35 +00:00
config.h.in libstdc++: Add std::from_chars for floating-point types 2020-07-20 23:49:27 +01:00
configure libstdc++: Exclude cygwin and mingw from linker relro support 2020-11-11 15:36:05 +00:00
configure.ac libstdc++: Add std::from_chars for floating-point types 2020-07-20 23:49:27 +01:00
configure.host Scope libstdc++ configuration for vxworks to all versions 2020-10-22 16:40:57 +00:00
crossconfig.m4 Scope libstdc++ configuration for vxworks to all versions 2020-10-22 16:40:57 +00:00
fragment.am
linkage.m4
Makefile.am build: Use -include instead of conditional include. 2020-06-22 21:31:48 +00:00
Makefile.in build: Use -include instead of conditional include. 2020-06-22 21:31:48 +00:00
README

README 

file: libstdc++-v3/README

New users may wish to point their web browsers to the file
index.html in the 'doc/html' subdirectory.  It contains brief
building instructions and notes on how to configure the library in
interesting ways.