On 64-bit CPU, there is padding in `RBasic`, so reorder the fields and use
it as buffer of embedded string. This change allows 4 more bytes to be
embedded on 64-bit CPU.
However, an incompatibility will occur if `RString::as::ary` is accessed
directly because `RString` structure has changed.
When building WebAssembly targets with clang (e.g. wasm32-unknown-unknown), all
symbols are hidden by default. To export a symbol, it must be marked with
__attribute__((visibility(default)))
Rather than detecting this exotic target in mruby, allow MRB_API to be defined
externally.
`mrb_string_value_cstr` and `mrb_string_value_len`: obsolete
`mrb_string_cstr`: new function to retrieve NULL terminated C string
`RSTRING_CSTR`: wrapper macro of `mrb_string_cstr`
Normal `TYPED_FIXABLE(f,mrb_float)` does not work on 64bit int from
casting problems. The new approach works well, but assumes two's
complement and IEEE-754 floating point numbers.
In #4550, @shuuji proposed the name name `MRB_STR_NO_MULTI_BYTE` for
more precise description. Although I agree that the name name is
correct, but the flag means the string does not contain multi byte UTF-8
characters, i.e. all characters fit in the range of ASCII.
Example:
$ bin/mruby -e '
p "あa".byteslice(1)
p "bar".byteslice(3)
p "bar".byteslice(4..0)
'
Before this patch:
"a"
""
RangeError (4..0 out of range)
After this patch (same as Ruby):
"\x81"
nil
nil
Before this patch:
$ bin/mruby -e 'p Struct.new("A-")'
#=> Struct::"A-"
After this patch:
$ bin/mruby -e 'p Struct.new("A-")'
#=> NameError: identifier A- needs to be constant
This time, the allocated memory comes from the string object, which is
referenced from GC arena. The memory region will be reclaimed when the C
function called from VM is terminated, or the GC arena is restored.
When I found this function, I expected it to behave the same as the
`alloca(3)` function, but it is accually the `mrb_alloca()` function
does not free the heap until the `mrb_close()` function is called.
Also, even if it is deleted, it can be replaced with the combination
of the `MRB_TT_DATA` object and the `mrb_gv_set()` function if it is
sure necessary.
Or `Float` if `mrb_float` value is too big (or too small) to fit in
`mrb_int`. The `_int_` in `mrb_int_value` means `Integral` module, which
represents integer-like values in mruby.
Not only mruby, it is one of the difficult things to adjust the performance vs. memory efficiency of the software.
If the approximate target device is divided and the adjustment value for it is prepared by default, it is a good indicator to do fine adjustment.
This PR divides into four profiles.
***Caution: There is no basis for the definitions in the patch.***
- `MRB_CONSTRAINED_BASELINE_PROFILE` - for microprocessors. Reduce memory consumption.
- `MRB_BASELINE_PROFILE` - Default value of mruby.
- `MRB_MAIN_PROFILE` - For desktop computers. Assume that a huge amount of RAM, 10 MiB or more, is on board.
- `MRB_HIGH_PROFILE` - for servers. Assume that mruby VM has a long life.
As you can see the profile name has been ~~stolen~~ imitated from H.264.
KOBAYASHI Shuji