Use Clang.jl to automate C wrapper

Project.toml

@@ -3,23 +3,24 @@ uuid = "76087f3c-5699-56af-9a33-bf431cd00edd"
 version = "1.0.2"
 
 [deps]
+CEnum = "fa961155-64e5-5f13-b03f-caf6b980ea82"
 MathOptInterface = "b8f27783-ece8-5eb3-8dc8-9495eed66fee"
 NLopt_jll = "079eb43e-fd8e-5478-9966-2cf3e3edb778"
 
+[weakdeps]
+MathOptInterface = "b8f27783-ece8-5eb3-8dc8-9495eed66fee"
+
+[extensions]
+NLoptMathOptInterfaceExt = ["MathOptInterface"]
+
 [compat]
 MathOptInterface = "1"
 NLopt_jll = "2.7"
 julia = "1.6"
 
-[extensions]
-NLoptMathOptInterfaceExt = ["MathOptInterface"]
-
 [extras]
 MathOptInterface = "b8f27783-ece8-5eb3-8dc8-9495eed66fee"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 
 [targets]
 test = ["MathOptInterface", "Test"]
-
-[weakdeps]
-MathOptInterface = "b8f27783-ece8-5eb3-8dc8-9495eed66fee"

gen/Project.toml

@@ -0,0 +1,6 @@
+[deps]
+Clang = "40e3b903-d033-50b4-a0cc-940c62c95e31"
+NLopt_jll = "079eb43e-fd8e-5478-9966-2cf3e3edb778"
+
+[compat]
+Clang = "0.17"

gen/gen.jl

@@ -0,0 +1,33 @@
+# Copyright (c) 2019 Mathieu Besançon, Oscar Dowson, and contributors
+#
+# Use of this source code is governed by an MIT-style license that can be found
+# in the LICENSE.md file or at https://opensource.org/licenses/MIT.
+
+using Clang.Generators
+import NLopt_jll
+
+c_api = joinpath(NLopt_jll.artifact_dir, "include", "nlopt.h")
+
+build!(
+    create_context(
+        [c_api],
+        get_default_args(),
+        load_options(joinpath(@__DIR__, "generate.toml")),
+    ),
+)
+
+header = """
+# Copyright (c) 2013: Steven G. Johnson and contributors
+#
+# Use of this source code is governed by an MIT-style license that can be found
+# in the LICENSE.md file or at https://opensource.org/licenses/MIT.
+
+#! format: off
+
+"""
+
+filename = joinpath(@__DIR__, "..", "src", "libnlopt.jl")
+contents = read(filename, String)
+contents = header * contents
+contents = replace(contents, "const nlopt_opt = Ptr{nlopt_opt_s}" => "const nlopt_opt = Ptr{Cvoid}")
+write(filename, contents)

gen/generate.toml

@@ -0,0 +1,7 @@
+[general]
+library_name = "libnlopt"
+output_file_path = "src/libnlopt.jl"
+# print_enum_as_integer = true
+# print_using_CEnum = false
+opaque_as_mutable_struct = false
+opaque_func_arg_as_PtrCvoid = true