mirror of
https://github.com/mruby/mruby
synced 2026-06-08 16:11:16 +00:00
Yukihiro "Matz" Matsumoto
dccd66f9ef
The Difference Since Ruby1.9, the keyword arguments were emulated by Ruby using the hash object at the bottom of the arguments. But we have gradually moved toward keyword arguments separated from normal (positinal) arguments. At the same time, we value compatibility, so that Ruby3.0 keyword arguments are somewhat compromise. Basically, keyword arguments are separated from positional arguments, except when the method does not take any formal keyword arguments, given keyword arguments (packed in the hash object) are considered as the last argument. And we also allow non symbol keys in the keyword arguments. In that case, those keys are just passed in the `**` hash (or raise `ArgumentError` for unknown keys). The Instruction Changes We have changed `OP_SEND` instruction. `OP_SEND` instruction used to take 3 operands, the register, the symbol, the number of (positional) arguments. The meaning of the third operand has been changed. It is now considered as `n|(nk<<4)`, where `n` is the number of positional arguments, and `nk` is the number of keyword arguments, both occupies 4 bits in the operand. The number `15` in both `n` and `nk` means variable sized arguments are packed in the object. Positional arguments will be packed in the array, and keyword arguments will be packed in the hash object. That means arguments more than 14 values are always packed in the object. Arguments information for other instructions (`OP_SENDB` and `OP_SUPER`) are also changed. It works as the third operand of `OP_SEND`. the difference between `OP_SEND` and `OP_SENDB` is just trivial. It assigns `nil` to the block hidden arguments (right after arguments). The instruction `OP_SENDV` and `OP_SENDVB` are removed. Those instructions are replaced by `OP_SEND` and `OP_SENDB` respectively with the `15` (variable sized) argument information. Calling Convention When calling a method, the stack elements shall be in the order of the receiver of the method, positional arguments, keyword arguments and the block argument. If the number of positional or keyword arugument (`n` or `nk`) is zero, corresponding arguments will be empty. So when `n=0` and `nk=0` the stack layout (from bottom to top) will be: +-----------------------+ | recv | block (or nil) | +-----------------------+ The last elements `block` should be explicitly filled before `OP_SEND` or assigned to `nil` by `OP_SENDB` internally. In other words, the following have exactly same behavior: OP_SENDB clears `block` implicitly: ``` OP_SENDB reg sym 0 ``` OP_SEND clears `block` implicitly: ``` OP_LOADNIL R2 OP_SEND R2 sym 0 ``` When calling a method with only positional arguments (n=0..14) without keyword arguments, the stack layout will be like following: +--------------------------------------------+ | recv | arg1 | ... | arg_n | block (or nil) | +--------------------------------------------+ When calling a method with arguments packed in the array (n=15) which means argument splat (*) is used in the actual arguments, or more than 14 arguments are passed the stack layout will be like following: +-------------------------------+ | recv | array | block (or nil) | +-------------------------------+ The number of the actual arguments is determined by the length of the argument array. When keyword arguments are given (nk>0), keyword arguments are passed between positional arguments and the block argument. For example, when we pass one positional argument `1` and one keyword argument `a: 2`, the stack layout will be like: +------------------------------------+ | recv | 1 | :a | 2 | block (or nil) | +------------------------------------+ Note that keyword arguments consume `2*nk` elements in the stack when `nk=0..14` (unpacked). When calling a method with keyword arguments packed in the hash object (nk=15) which means keyword argument splat (**) is used or more than 14 keyword arguments in the actual arguments, the stack layout will be like: +------------------------------+ | recv | hash | block (or nil) | +------------------------------+ Note for mruby/c When mruby/c authors try to support new keyword arguments, they need to handle the new meaning of the argument information operand. If they choose not to support keyword arguments in mruby/c, it just raise error when `nk` (taken by `(c>>4)&0xf`) is not zero. And combine `OP_SENDV` behavior with `OP_SEND` when `n` is `15`. If they want to support keyword arguments seriously, contact me at <matz@ruby.or.jp> or `@yukihiro_matz`. I can help you.
155 lines
4.6 KiB
Markdown
155 lines
4.6 KiB
Markdown
# User visible changes in `mruby3`
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# Build System
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## `build_config` directory
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Typical build configuration files are located in `build_config`
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directory. For examples:
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* `default`: the default configuration
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* `host-gprof`: compiles with `gprof` for performance tuning
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* `host-m32`: compiles in gcc 32bit mode on 64bit platforms
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* `boxing`: compiles all three boxing options
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* `clang-asan`: compiles with `clang`'s Address Sanitizer
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You can specify the build configuration file with the
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`MRUBY_CONFIG` environment variable (or `CONFIG` in short).
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If the value specified by `MRUBY_CONFIG` is not the path to
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the configuration file, `build_config/${MRUBY_CONFIG}.rb` is
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used. So you can specify it as `rake MRUBY_CONFIG=boxing`,
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for example.
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# Build Configuration Contribution
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When you write a new build configuration description, please
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contribute. We welcome your contribution as a GitHub
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pull-request.
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# Language Changes
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## New Syntax
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We have ported some new syntax from CRuby.
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* Single line pattern matching (`12 => x`);
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mruby matches only with local variables at the moment
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* Numbered block parameter (`x.map{_1 * 2}`)
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* End-less `def` (`def double(x) = x*2`)
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# Configuration Options Changed
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## Renamed for consistency
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Some configuration macro names are changed for consistency (use `MRB_USE_XXX`
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or `MRB_NO_XXX`).
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| mruby2 | mruby3 |
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|--------------------------------|---------------------------|
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| `MRB_ENABLE_ALL_SYMBOLS` | `MRB_USE_ALL_SYMBOLS` |
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| `MRB_ENABLE_CXX_ABI` | `MRB_USE_CXX_ABI` |
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| `MRB_ENABLE_CXX_EXCEPTION` | `MRB_USE_CXX_EXCEPTION` |
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| `MRB_ENABLE_DEBUG_HOOK` | `MRB_USE_DEBUG_HOOK` |
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| `MRB_DISABLE_DIRECT_THREADING` | `MRB_NO_DIRECT_THREADING` |
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| `MRB_DISABLE_STDIO` | `MRB_NO_STDIO` |
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| `MRB_METHOD_T_STRUCT` | `MRB_USE_METHOD_T_STRUCT` |
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| `MRB_USE_FLOAT` | `MRB_USE_FLOAT32` |
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| `MRB_WITHOUT_FLOAT` | `MRB_NO_FLOAT` |
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| `ENABLE_LINENOISE` | `MRB_USE_LINENOISE` |
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| `ENABLE_READLINE` | `MRB_USE_READLINE` |
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| `DISABLE_MIRB_UNDERSCORE` | `MRB_NO_MIRB_UNDERSCORE` |
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* `MRB_USE_FLOAT32` is changed from `MRB_USE_FLOAT` to make sure `float` here
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means using single precision float, and not the opposite of `MRB_NO_FLOAT`.
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* `MRB_USE_METHOD_T_STRUCT` uses `struct` version of `mrb_method_t`. More
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portable but consumes more memory. Turned on by default on 32bit platforms.
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* `MRB_` prefix is added to those without.
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## `MRB_NO_BOXING`
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Uses `struct` to represent `mrb_value`. Consumes more memory
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but easier to investigate the internal and to debug. It used
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to be default `mrb_value` representation. Now the default is
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`MRB_WORD_BOXING`.
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## `MRB_WORD_BOXING`
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Pack `mrb_value` in an `intptr_t` integer. Consumes less
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memory compared to `MRB_NO_BOXING` especially on 32-bit
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platforms. Inlined integer size is 31 bits, so some `mrb_int`
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values does not fit in `mrb_value`. Those integers are allocated
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in the object heap as `struct RInteger`.
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## `MRB_NAN_BOXING`
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Pack `mrb_value` in a floating-point number. Nothing
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changed from previous versions.
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## `MRB_USE_MALLOC_TRIM`
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Call `malloc_trim(0)` from mrb_full_gc() if this macro is defined.
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If you are using glibc malloc, this macro could reduce memory consumption.
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# Command Line Program
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## `bin/mruby` (by mrbgems/mruby-bin-mruby)
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The mruby3 now automatically detects `*.mrb` files without the `-b`
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switch. Therefore, it can be mixed with the `*.rb` file in combination
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with the `-r` switch and specified at the same time.
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Here's an example that works fine:
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```console
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$ bin/mruby app.mrb
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$ bin/mruby -r lib1.mrb -r lib2.rb app.rb
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$ bin/mruby -r lib1.rb -r lib2.rb < app.mrb
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```
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# Internal Changes
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## New Instructions
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`mruby3` introduces a few new instructions.
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Instructions that load a 16/32-bit integer.
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* `OP_LOADI16`
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* `OP_LOADI32`
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Instruction that unwinds jump table for rescue/ensure.
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* `OP_JMPUW`
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Renamed from `OP_RAISE`
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* `OP_RAISEIF`
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## Removed Instructions
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Instructions for old exception handling
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* `OP_ONERR`
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* `OP_POPERR`
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* `OP_EPUSH`
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* `OP_EPOP`
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No more operand extension
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* `OP_EXT1`
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* `OP_EXT2`
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* `OP_EXT3`
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## Changed Instructions
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Jump addresses used to be specified by absolute offset from the start of `iseq`. Now they are relative offset from the address of the next instruction.
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## `Random` now use `xoshiro128++`
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For better and faster random number generation.
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## Preallocated Symbol
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Preallocated symbols are interned at compile-time. They can be accessed via symbols macros (e.g. `MRB_SYM()`).
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See [Symbols](./guides/symbol.md).
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