Add a JS_ENUMERATE_INTL_OBJECTS macro and use it to generate:
- Forward declarations
- CommonPropertyNames class name members
- Constructor and prototype GlobalObject members, getters, visitors,
and initialize_constructor() calls
This is the start of implementing ECMA-402 in LibJS, better known as the
ECMAScript Internationalization API.
Much like Temporal this gets its own subdirectory (Runtime/Intl/) as
well as a new C++ namespace (JS::Intl) so we don't have to prefix all
the files and classes with "Intl".
https://tc39.es/ecma402/
This commit adds the PlainYearMonth object itself, its constructor and
prototype (currently empty), and the CreateTemporalYearMonth and
ISOYearMonthWithinLimits abstract operations.
Although this is not spec-compliant, we don't have a way to represent
objects larger than `NumericLimits<size_t>::max()`. Since this abstract
operation is only used when dealing with object size, we don't lose any
functionality by taking that limit into account too.
This fixes a UBSAN error when compiling with Clang.
If we call these two functions on a negative value, undefined behavior
occurs due to casting a negative double to an unsigned integer. These
functions are defined to perform modular arithmetic, so negative values
can be fixed up by adding 2^8/2^16.
The reason why this step is not mentioned in ECMA-262 is that it defines
modular arithmetic so that `x mod m` had the same sign as `m`, while
LibM's `fmod(x, m)` copies `x`'s sign.
This issue was found by UBSAN with the Clang toolchain.
Casting a floating point number to an integer and comparing that against
the original value is not a good way to test if it is a whole number. It
may cause unnecessary narrowing conversion issues and UB. This was the
case, which was caught be Clang's `-fsanitize=float-cast-overflow`.
This commit changes the code to use `is_integral_number`, as suggested
in ECMA-262.
If the argument to this function is greater then or equal to 2^32, the
`double` => `u32` cast produces undefined behavior, which Clang catches.
To fix this, we now use `ToUint32` for getting the integer argument, as
specified by ECMA-262.
length is size_t as returned, and so subtracting from it may cause
underflow. We handle this case by just casting it to a signed value, and
the for loop predicate takes care of the rest.
