Segfault in ccall

[jw3126]

From discourse. The following code segfaults for me:

C = """
typedef struct CParticle {
    double charge;
    double E;
    double weight;
} CParticle;


void simulate(void (*f)(CParticle x)) {
    CParticle cp;
    cp.charge = 0;
    cp.E = 1;
    cp.weight = 2;
    (*f)(cp);
    return;
}

"""

struct CParticle
    charge::Cdouble
    E::Cdouble
    weight::Cdouble
end

write("lib.c", C)
run(`gcc -c -fPIC lib.c -o lib.o`)
run(`gcc -shared lib.o -o lib.so`)
lib = "./lib.so"

function main()
    ret = CParticle[]
    f = x::CParticle -> (push!(ret, x); nothing)
    f_c = @cfunction $f Cvoid (CParticle,)
    GC.@preserve ret f f_c begin # AFAICT I don't need to GC.@preserver here
        @ccall lib.simulate(f_c::Ptr{Cvoid})::Cvoid
    end
    @show ret
end

main()

I read the manual and in particular the section about closures, but I am still not sure where the error lies.
It works, if I do one of the following:

• make the CParticle struct smaller e.g. only charge + weight fields
• execute the main code globally
• don't call push! in the callback

@Gnimuc pointed out workarounds, but it is still unclear why this happens, and would be nice to fix it or document it. I can help with the latter.

[JeffBezanson]

Attributes 'byval', 'inalloca', 'preallocated', 'inreg', 'nest', and 'sret' are incompatible!
void ({} addrspace(10)**, [3 x double] addrspace(11)*)* @"jlcapi_#3_256"
julia: /workspace/srcdir/llvm-project/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp:2369: llvm::slpvectorizer::BoUpSLP::~BoUpSLP(): Assertion `!verifyFunction(*F, &dbgs())' failed.

signal (6): Aborted
in expression starting at REPL[17]:1
gsignal at /lib/x86_64-linux-gnu/libc.so.6 (unknown line)
abort at /lib/x86_64-linux-gnu/libc.so.6 (unknown line)
unknown function (ip: 0x7f1167b3d728)
__assert_fail at /lib/x86_64-linux-gnu/libc.so.6 (unknown line)
_ZN4llvm13slpvectorizer7BoUpSLPD1Ev at /home/jeff/src/julia/usr/bin/../lib/libLLVM-11jl.so (unknown line)
_ZN4llvm17SLPVectorizerPass7runImplERNS_8FunctionEPNS_15ScalarEvolutionEPNS_19TargetTransformInfoEPNS_17TargetLibraryInfoEPNS_9AAResultsEPNS_8LoopInfoEPNS_13DominatorTreeEPNS_15AssumptionCacheEPNS_12DemandedBitsEPNS_25OptimizationRemarkEmitterE.part.1527 at /home/jeff/src/julia/usr/bin/../lib/libLLVM-11jl.so (unknown line)
_ZN12_GLOBAL__N_113SLPVectorizer13runOnFunctionERN4llvm8FunctionE at /home/jeff/src/julia/usr/bin/../lib/libLLVM-11jl.so (unknown line)
_ZN4llvm13FPPassManager13runOnFunctionERNS_8FunctionE at /home/jeff/src/julia/usr/bin/../lib/libLLVM-11jl.so (unknown line)

[ViralBShah]

Just tried the code snippet on mac with Julia master (1.9-dev) and I don't get a segfault on mac.

[vtjnash]

Fixed by #41827, but it didn't use any of the magic words for auto-closing

[jw3126]

Works for me thanks @troels and everybody else for fixing this.