[sledge] Switch from Llvm.demangle to __cxa_demangle via Ctypes

Summary:
Call __cxa_demangle from libstdc++ using Ctypes instead of the
wrapper in Llvm.

Reviewed By: mbouaziz

Differential Revision: D9939682

fbshipit-source-id: a9f02fff5

sledge/llair.opam

@@ -10,6 +10,8 @@ build: [
 depends: [
   "cmdliner"
   "core_kernel" {>= "v0.11.0"}
+  "ctypes"
+  "ctypes-foreign"
   "dune" {build}
   "llvm" {build & = "7.0.0"}
   "ppx_compare" {>= "v0.11.0"}

sledge/sledge.opam

@@ -10,6 +10,8 @@ build: [
 depends: [
   "cmdliner"
   "core_kernel" {>= "v0.11.0"}
+  "ctypes"
+  "ctypes-foreign"
   "dune" {build}
   "llvm" {build & = "7.0.0"}
   "ppx_compare" {>= "v0.11.0"}

sledge/src/llair/dune.in

@@ -10,6 +10,6 @@ Jbuild_plugin.V1.send
  (name llair_)
  (public_name llair)
  %s
- (libraries llvm llvm.irreader llvm.analysis llvm.scalar_opts llvm.target %s))
+ (libraries ctypes ctypes.foreign llvm llvm.irreader llvm.analysis llvm.scalar_opts llvm.target %s))
 |}
      (flags deps) (libraries deps)

sledge/src/llair/global.ml

@@ -12,6 +12,23 @@ type t = {var: Var.t; init: Exp.t option; siz: int; typ: Typ.t; loc: Loc.t}
 
 let equal = [%compare.equal: t]
 
+let demangle =
+  let open Ctypes in
+  let cxa_demangle =
+    (* char *__cxa_demangle(const char *, char *, size_t *, int * ) *)
+    Foreign.foreign "__cxa_demangle"
+      ( string @-> ptr char @-> ptr size_t @-> ptr int
+      @-> returning string_opt )
+  in
+  let null_ptr_char = from_voidp char null in
+  let null_ptr_size_t = from_voidp size_t null in
+  let status = allocate int 0 in
+  fun mangled ->
+    let demangled =
+      cxa_demangle mangled null_ptr_char null_ptr_size_t status
+    in
+    if !@status = 0 then demangled else None
+
 let pp fs {var} =
   let name = Var.name var in
   let pf pp =
@@ -19,9 +36,10 @@ let pp fs {var} =
     Format.kfprintf (fun fs -> Format.pp_close_box fs ()) fs pp
   in
   pf "@%s%t" name (fun fs ->
-      let demangled = Llvm.demangle name in
-      if not (String.is_empty demangled || String.equal name demangled) then
-        Format.fprintf fs "“%s”" demangled )
+      match demangle name with
+      | Some demangled when not (String.equal name demangled) ->
+          Format.fprintf fs "“%s”" demangled
+      | _ -> () )
 
 let pp_defn fs {var; init; typ} =
   Format.fprintf fs "@[<2>%a %a%a@]" Typ.pp typ Var.pp var