[sledge][llvm] Resolve const and unsigned compilation warnings

Summary:
There are a number of compilation warnings regarding disregarding
const qualifiers, and casting between pointers to integer types with
different sign.

The incompatible sign warnings are due to treating the result of
`LLVMGetModuleIdentifier` as `const unsigned char *`, but it is
declared as `const char *`.

The dropped const qualifiers are due to the code pattern
`memcpy(String_val(_),_,_)` which ought to be (following the
implementation of the OCaml runtime)
`memcpy((char *)String_val(_),_,_)`. The issue is that `String_val` is
usually used to get the value of an immutable string. But in the
context of the `memcpy` calls, the string is in the process of being
initialized, so is not yet constant.

Upstream Differential Revision: https://reviews.llvm.org/D99392

Reviewed By: ngorogiannis

Differential Revision: D27360846

fbshipit-source-id: d045ad7c0

sledge/vendor/llvm-dune/llvm-project/llvm/bindings/ocaml/llvm/llvm_ocaml.c

@@ -76,7 +76,7 @@ CAMLprim value llvm_enable_pretty_stacktrace(value Unit) {
 }
 
 CAMLprim value llvm_parse_command_line_options(value Overview, value Args) {
-  char *COverview;
+  const char *COverview;
   if (Overview == Val_int(0)) {
     COverview = NULL;
   } else {
@@ -247,7 +247,7 @@ CAMLprim value llvm_get_string_attr_kind(LLVMAttributeRef A) {
   unsigned Length;
   const char *String = LLVMGetStringAttributeKind(A, &Length);
   value Result = caml_alloc_string(Length);
-  memcpy(String_val(Result), String, Length);
+  memcpy((char *)String_val(Result), String, Length);
   return Result;
 }
 
@@ -256,7 +256,7 @@ CAMLprim value llvm_get_string_attr_value(LLVMAttributeRef A) {
   unsigned Length;
   const char *String = LLVMGetStringAttributeValue(A, &Length);
   value Result = caml_alloc_string(Length);
-  memcpy(String_val(Result), String, Length);
+  memcpy((char *)String_val(Result), String, Length);
   return Result;
 }
 
@@ -839,7 +839,7 @@ CAMLprim value llvm_get_mdstring(LLVMValueRef V) {
 
   if ((S = LLVMGetMDString(V, &Len))) {
     Str = caml_alloc_string(Len);
-    memcpy(String_val(Str), S, Len);
+    memcpy((char *)String_val(Str), S, Len);
     Option = alloc(1,0);
     Store_field(Option, 0, Str);
     CAMLreturn(Option);
@@ -1117,7 +1117,7 @@ CAMLprim value llvm_string_of_const(LLVMValueRef Const) {
   if(LLVMIsAConstantDataSequential(Const) && LLVMIsConstantString(Const)) {
     S = LLVMGetAsString(Const, &Len);
     Str = caml_alloc_string(Len);
-    memcpy(String_val(Str), S, Len);
+    memcpy((char *)String_val(Str), S, Len);
 
     Option = alloc(1, 0);
     Field(Option, 0) = Str;
@@ -2640,7 +2640,7 @@ CAMLprim LLVMMemoryBufferRef llvm_memorybuffer_of_string(value Name, value Strin
 /* llmemorybuffer -> string */
 CAMLprim value llvm_memorybuffer_as_string(LLVMMemoryBufferRef MemBuf) {
   value String = caml_alloc_string(LLVMGetBufferSize(MemBuf));
-  memcpy(String_val(String), LLVMGetBufferStart(MemBuf),
+  memcpy((char *)String_val(String), LLVMGetBufferStart(MemBuf),
          LLVMGetBufferSize(MemBuf));
 
   return String;

sledge/vendor/llvm-dune/llvm-project/llvm/bindings/ocaml/target/target_ocaml.c

@@ -314,7 +314,7 @@ CAMLprim value llvm_targetmachine_emit_to_file(LLVMModuleRef Module,
   char *ErrorMessage;
 
   if(LLVMTargetMachineEmitToFile(TargetMachine_val(Machine), Module,
-                                 String_val(FileName), Int_val(FileType),
+                                 (char *)String_val(FileName), Int_val(FileType),
                                  &ErrorMessage)) {
     llvm_raise(*caml_named_value("Llvm_target.Error"), ErrorMessage);
   }

sledge/vendor/llvm-dune/llvm-project/llvm/bindings/ocaml/transforms/ipo/ipo_ocaml.c

@@ -123,7 +123,7 @@ LLVMBool MustPreserveCallBack(LLVMValueRef Val, void* Ctx) {
 
 /* [`Module] Llvm.PassManager.t -> unit */
 CAMLprim value llvm_add_internalize_predicate(LLVMPassManagerRef PM) {
-  predicate_f = caml_named_value("LLVMInternalizePredicateCallback");
+  predicate_f = (value *)caml_named_value("LLVMInternalizePredicateCallback");
   LLVMAddInternalizePassWithMustPreservePredicate(PM, NULL,
                                                   &MustPreserveCallBack);
   return Val_unit;