rustc_codegen_llvm: use safe references for ThinLTOBuffer.

Author: irinagpopa

src/librustc_codegen_llvm/back/lto.rs

@@ -579,7 +579,7 @@ impl Drop for ThinData {
     }
 }
 
-pub struct ThinBuffer(*mut llvm::ThinLTOBuffer);
+pub struct ThinBuffer(&'static mut llvm::ThinLTOBuffer);
 
 unsafe impl Send for ThinBuffer {}
 unsafe impl Sync for ThinBuffer {}
@@ -604,7 +604,7 @@ impl ThinBuffer {
 impl Drop for ThinBuffer {
     fn drop(&mut self) {
         unsafe {
-            llvm::LLVMRustThinLTOBufferFree(self.0);
+            llvm::LLVMRustThinLTOBufferFree(&mut *(self.0 as *mut _));
         }
     }
 }

src/librustc_codegen_llvm/llvm/ffi.rs

@@ -1571,10 +1571,10 @@ extern "C" {
 
     pub fn LLVMRustThinLTOAvailable() -> bool;
     pub fn LLVMRustPGOAvailable() -> bool;
-    pub fn LLVMRustThinLTOBufferCreate(M: &Module) -> *mut ThinLTOBuffer;
-    pub fn LLVMRustThinLTOBufferFree(M: *mut ThinLTOBuffer);
-    pub fn LLVMRustThinLTOBufferPtr(M: *const ThinLTOBuffer) -> *const c_char;
-    pub fn LLVMRustThinLTOBufferLen(M: *const ThinLTOBuffer) -> size_t;
+    pub fn LLVMRustThinLTOBufferCreate(M: &Module) -> &'static mut ThinLTOBuffer;
+    pub fn LLVMRustThinLTOBufferFree(M: &'static mut ThinLTOBuffer);
+    pub fn LLVMRustThinLTOBufferPtr(M: &ThinLTOBuffer) -> *const c_char;
+    pub fn LLVMRustThinLTOBufferLen(M: &ThinLTOBuffer) -> size_t;
     pub fn LLVMRustCreateThinLTOData(
         Modules: *const ThinLTOModule,
         NumModules: c_uint,