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Use support for gc_safe=true in Base if available #6

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Use support for gc_safe=true in Base if available #6

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0a027f5
Use support for gc_safe=true in Base if available
vchuravy Feb 17, 2025
9e36de8
fixup! Use support for gc_safe=true in Base if available
vchuravy Feb 17, 2025
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36 changes: 22 additions & 14 deletions src/ccalls.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -91,13 +91,31 @@ render_arg(io, arg::Base.RefValue{T}) where {T} = print(io, "Ref{", T, "}")


## version of ccall that calls jl_gc_safe_enter|leave around the inner ccall

# TODO: replace with JuliaLang/julia#49933 once merged

# note that this is generally only safe with functions that do not call back into Julia.
# when callbacks occur, the code should ensure the GC is not running by wrapping the code
# in the `@gcunsafe` macro

const HAS_CCALL_GCSAFE = VERSION >= v"1.13.0-DEV.70"
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Wait for JuliaLang/julia#57408 to be merged to add that compat/version bound to this PR?

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Suggested change
const HAS_CCALL_GCSAFE = VERSION >= v"1.13.0-DEV.70"
const HAS_CCALL_GCSAFE = VERSION >= v"1.13.0-DEV.70" || v"1.12-DEV.2029" <= VERSION < v"1.13-"


"""
@gcsafe_ccall ...

Call a foreign function just like `@ccall`, but marking it safe for the GC to run. This is
useful for functions that may block, so that the GC isn't blocked from running, but may also
be required to prevent deadlocks (see JuliaGPU/CUDA.jl#2261).

Note that this is generally only safe with non-Julia C functions that do not call back into
Julia. When using callbacks, the code should make sure to transition back into GC-unsafe
mode using the `@gcunsafe` macro.
"""
macro gcsafe_ccall end

if HAS_CCALL_GCSAFE
macro gcsafe_ccall(exprs)
exprs = pushfirst(exprs, :(gc_safe = true))
return Base.ccall_macro_lower((:ccall), Base.ccall_macro_parse(exprs)...)
end
else
function ccall_macro_lower(func, rettype, types, args, nreq)
# instead of re-using ccall or Expr(:foreigncall) to perform argument conversion,
# we need to do so ourselves in order to insert a jl_gc_safe_enter|leave
Expand Down Expand Up @@ -138,17 +156,7 @@ function ccall_macro_lower(func, rettype, types, args, nreq)
end
end

"""
@gcsafe_ccall ...

Call a foreign function just like `@ccall`, but marking it safe for the GC to run. This is
useful for functions that may block, so that the GC isn't blocked from running, but may also
be required to prevent deadlocks (see JuliaGPU/CUDA.jl#2261).

Note that this is generally only safe with non-Julia C functions that do not call back into
Julia. When using callbacks, the code should make sure to transition back into GC-unsafe
mode using the `@gcunsafe` macro.
"""
macro gcsafe_ccall(expr)
return ccall_macro_lower(Base.ccall_macro_parse(expr)...)
end
end # HAS_CCALL_GCSAFE
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