RB_GC_GUARD support or something else to ensure VALUE is on the stack

[uvlad7]

This macro is used to protect VALUEs from being GC-ed while they are still in use indirectly (or even directly, as otherwise it may be placed in a register, not on the stack). If for some reason it's not possible to use RB_GC_GUARD from memory.h, another solutions probably exist, as it's a common problem when interacting with conservative GCs. And I believe it should be mentioned in the readme.

[uvlad7]

UPD: it says registers are ok in ruby, but RB_GC_GUARD is still needed in some cases

[sue445]

I see. I'll try to figure out if it is possible to automatically generate bindings for C macros.

[uvlad7]

You may want to look how it's done in rb-sys
As for macro parsing, maybe rbgccxml is worth a look? Won't work out of the box, but may inspire ruby_header_parser

[uvlad7]

Stumbled upon Python's cffi, it uses pycparser - common approach is to preprocess headers with cpp and feed them into cffi - and thought maybe it's worth to use it here too.

Also, I have a question about compatibility, where will it fail if a signature of a function is changed or it's removed completely? For example, Rust rb-sys uses bindgen during gem compilation, so if a function is changed/removed, later usages will become invalid and it'll fail. Important part here is that it uses exactly the same header that is used by regular C native extensions. But I guess Go will use a pregenated version, right, which contains definitions parsed from ruby.h? If so, it'll fail on link time if the function is deleted and probably on run time if signature is changed.

[sue445]

@uvlad7 Sorry for the late reply.

As for macro parsing, maybe rbgccxml is worth a look?

https://github.com/jasonroelofs/rbgccxml uses https://github.com/CastXML/CastXML internally.

Therefore, I tried using CastXML directly, but it seemed that the macro function information could not be expanded.

e.g.

# sum.h #define SUM(a, b) ((a) + (b))

$ castxml -Wno-unused-command-line-argument --castxml-cc-gnu-c /usr/bin/clang --castxml-gccxml sum.h -o sum.h.xml

Body of sum.h.xml

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location="f0:0" file="f0" line="0"/> <Typedef id="_9" name="__SVUint8_t" type="_71" context="_1" location="f0:0" file="f0" line="0"/> <Typedef id="_10" name="__SVUint16_t" type="_72" context="_1" location="f0:0" file="f0" line="0"/> <Typedef id="_11" name="__SVUint32_t" type="_73" context="_1" location="f0:0" file="f0" line="0"/> <Typedef id="_12" name="__SVUint64_t" type="_74" context="_1" location="f0:0" file="f0" line="0"/> <Typedef id="_13" name="__SVFloat16_t" type="_75" context="_1" location="f0:0" file="f0" line="0"/> <Typedef id="_14" name="__SVFloat32_t" type="_76" context="_1" location="f0:0" file="f0" line="0"/> <Typedef id="_15" name="__SVFloat64_t" type="_77" context="_1" location="f0:0" file="f0" line="0"/> <Typedef id="_16" name="__SVBfloat16_t" type="_78" context="_1" location="f0:0" file="f0" line="0"/> <Typedef id="_17" name="__SVMfloat8_t" type="_79" context="_1" location="f0:0" file="f0" line="0"/> <Typedef id="_18" name="__clang_svint8x2_t" type="_80" context="_1" 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Stumbled upon Python's cffi, it uses pycparser

I checked out https://github.com/eliben/pycparser .

However, it was found that the AST of macro functions cannot be obtained in pycparser.

e.g.

# sum.c #define SUM(a, b) ((a) + (b)) int foo() {} int main() { foo(); return 0; }

$ python examples/using_gcc_E_libc.py /path/to/sum.c FileAST: FuncDef: Decl: foo, [], [], [], [] FuncDecl: TypeDecl: foo, [], None IdentifierType: ['int'] Compound: FuncDef: Decl: main, [], [], [], [] FuncDecl: TypeDecl: main, [], None IdentifierType: ['int'] Compound: FuncCall: ID: foo Return: Constant: int, 0

Also, I have a question about compatibility, where will it fail if a signature of a function is changed or it's removed completely?

An error occurs during build.

However, Ruby doesn't add or remove features within the same minor version.

Therefore, go-gem-wrapper uses different bindings for each minor version of Ruby.

e.g.

• https://github.com/ruby-go-gem/go-gem-wrapper/blob/v0.7.3/ruby/function_ruby_3_3_generated.go
• https://github.com/ruby-go-gem/go-gem-wrapper/blob/v0.7.3/ruby/function_ruby_3_4_generated.go

See also

https://speakerdeck.com/sue445/road-to-go-gem-number-rubykaigi?slide=95

[sue445]

I implemented RB_GC_GUARD at #323.

In addition, I have provided comments automatic generation of macro functions at #324.