codegen: parameter attributes on CFunction closures sticks (JuliaLang#41827)

When CFunction closures are created an extra argument is added to the
function signature for holding the closure.

Make sure that the parameter attributes on already existing parameters
are not shifted when adding that parameter.

Author: troels

src/codegen.cpp

@@ -5180,9 +5180,48 @@ static Function* gen_cfun_wrapper(
         // add nest parameter (pointer to jl_value_t* data array) after sret arg
         assert(closure_types);
         std::vector<Type*> fargt_sig(sig.fargt_sig);
+
         fargt_sig.insert(fargt_sig.begin() + sig.sret, T_pprjlvalue);
+
+        // Shift LLVM attributes for parameters one to the right, as
+        // we are adding the extra nest parameter after sret arg.
+        std::vector<std::pair<unsigned, AttributeSet>> newAttributes;
+        newAttributes.reserve(attributes.getNumAttrSets() + 1);
+        auto it = attributes.index_begin();
+
+        // Skip past FunctionIndex
+        if (it == AttributeList::AttrIndex::FunctionIndex) {
+            ++it;
+        }
+
+        // Move past ReturnValue and parameter return value
+        for (;it < AttributeList::AttrIndex::FirstArgIndex + sig.sret; ++it) {
+            if (attributes.hasAttributes(it)) {
+                newAttributes.emplace_back(it, attributes.getAttributes(it));
+            }
+        }
+
+        // Add the new nest attribute
+        AttrBuilder attrBuilder;
+        attrBuilder.addAttribute(Attribute::Nest);
+        newAttributes.emplace_back(it, AttributeSet::get(jl_LLVMContext, attrBuilder));
+
+        // Shift forward the rest of the attributes
+        for(;it < attributes.index_end(); ++it) {
+            if (attributes.hasAttributes(it)) {
+                newAttributes.emplace_back(it + 1, attributes.getAttributes(it));
+            }
+        }
+
+        // Remember to add back FunctionIndex
+        if (attributes.hasAttributes(AttributeList::AttrIndex::FunctionIndex)) {
+            newAttributes.emplace_back(AttributeList::AttrIndex::FunctionIndex,
+                                       attributes.getAttributes(AttributeList::AttrIndex::FunctionIndex));
+        }
+
+        // Create the new AttributeList
+        attributes = AttributeList::get(jl_LLVMContext, newAttributes);
         functype = FunctionType::get(sig.sret ? T_void : sig.prt, fargt_sig, /*isVa*/false);
-        attributes = attributes.addAttribute(jl_LLVMContext, 1 + sig.sret, Attribute::Nest);
     }
     else {
         functype = sig.functype();

test/ccall.jl

@@ -982,6 +982,26 @@ for (t, v) in ((Complex{Int32}, :ci32), (Complex{Int64}, :ci64),
     end
 end
 
+
+#issue 40164
+@testset "llvm parameter attributes on cfunction closures" begin
+    struct Struct40164
+        x::Cdouble
+        y::Cdouble
+        z::Cdouble
+    end
+
+    function test_40164()
+        ret = Struct40164[]
+        f = x::Struct40164 -> (push!(ret, x); nothing)
+        f_c = @cfunction($f, Cvoid, (Struct40164,))
+        ccall(f_c.ptr, Ptr{Cvoid}, (Struct40164,), Struct40164(0, 1, 2))
+        ret
+    end
+
+    @test test_40164() == [Struct40164(0, 1, 2)]
+end
+
 else
 
 @test_broken "cfunction: no support for closures on this platform"