From 2cbf4afa99a1a8953ed54abdcb292b45b79a8639 Mon Sep 17 00:00:00 2001
From: Christian Poveda <christianpoveda@protonmail.com>
Date: Fri, 11 Oct 2019 00:55:32 -0500
Subject: [PATCH] Split `write_c_ints` into less specific helper functions

---
 src/helpers.rs    | 39 +++++++++++++++------------------------
 src/shims/time.rs | 40 ++++++++++++++++++++++++++++++++++++----
 2 files changed, 51 insertions(+), 28 deletions(-)

diff --git a/src/helpers.rs b/src/helpers.rs
index fea2307dcca5..892ba7b2401b 100644
--- a/src/helpers.rs
+++ b/src/helpers.rs
@@ -4,7 +4,7 @@ use rustc::hir::def_id::{DefId, CRATE_DEF_INDEX};
 use rustc::mir;
 use rustc::ty::{
     self,
-    layout::{self, Align, LayoutOf, Size},
+    layout::{self, Align, LayoutOf, Size, TyLayout},
 };
 
 use rand::RngCore;
@@ -308,42 +308,26 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         self.eval_libc(name)?.to_i32()
     }
 
-    fn write_c_ints(
+    // Writes several `ImmTy`s contiguosly into memory. This is useful when you have to pack
+    // different values into an struct.
+    fn write_immediates(
         &mut self,
         ptr: &Pointer<Tag>,
-        bits: &[i128],
-        ty_names: &[&str],
+        imms: &[ImmTy<'tcx, Tag>],
     ) -> InterpResult<'tcx> {
         let this = self.eval_context_mut();
 
         let tcx = &{ this.tcx.tcx };
 
-        let mut sizes = Vec::new();
-
-        for name in ty_names {
-            let ty = this.resolve_path(&["libc", name])?.ty(*tcx);
-            sizes.push(this.layout_of(ty)?.size);
-        }
-
         let allocation = this.memory_mut().get_mut(ptr.alloc_id)?;
         let mut offset = Size::from_bytes(0);
 
-        for (&value, size) in bits.iter().zip(sizes) {
-            // If `value` does not fit in `size` bits, we error instead of letting
-            // `Scalar::from_int` panic.
-            let truncated = truncate(value as u128, size);
-            if sign_extend(truncated, size) as i128 != value {
-                throw_unsup_format!(
-                    "Signed value {:#x} does not fit in {} bits",
-                    value,
-                    size.bits()
-                )
-            }
-
+        for imm in imms {
+            let size = imm.layout.size;
             allocation.write_scalar(
                 tcx,
                 ptr.offset(offset, tcx)?,
-                Scalar::from_int(value, size).into(),
+                imm.to_scalar()?.into(),
                 size,
             )?;
             offset += size;
@@ -351,4 +335,11 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
 
         Ok(())
     }
+
+    fn libc_ty_layout(&mut self, name: &str) -> InterpResult<'tcx, TyLayout<'tcx>> {
+        let this = self.eval_context_mut();
+        let tcx = &{ this.tcx.tcx };
+        let ty = this.resolve_path(&["libc", name])?.ty(*tcx);
+        this.layout_of(ty)
+    }
 }
diff --git a/src/shims/time.rs b/src/shims/time.rs
index 2995bdc43464..3acc84dbc751 100644
--- a/src/shims/time.rs
+++ b/src/shims/time.rs
@@ -1,8 +1,12 @@
+use std::time::{Duration, SystemTime};
+
+use rustc::ty::layout::TyLayout;
+
 use crate::stacked_borrows::Tag;
 use crate::*;
 
-use std::time::{Duration, SystemTime};
-
+// Returns the time elapsed between now and the unix epoch as a `Duration` and the sign of the time
+// interval
 fn get_time() -> (Duration, i128) {
     let mut sign = 1;
     let duration = SystemTime::now()
@@ -14,6 +18,24 @@ fn get_time() -> (Duration, i128) {
     (duration, sign)
 }
 
+fn int_to_immty_checked<'tcx>(
+    int: i128,
+    layout: TyLayout<'tcx>,
+) -> InterpResult<'tcx, ImmTy<'tcx, Tag>> {
+    // If `int` does not fit in `size` bits, we error instead of letting
+    // `ImmTy::from_int` panic.
+    let size = layout.size;
+    let truncated = truncate(int as u128, size);
+    if sign_extend(truncated, size) as i128 != int {
+        throw_unsup_format!(
+            "Signed value {:#x} does not fit in {} bits",
+            int,
+            size.bits()
+        )
+    }
+    Ok(ImmTy::from_int(int, layout))
+}
+
 impl<'mir, 'tcx> EvalContextExt<'mir, 'tcx> for crate::MiriEvalContext<'mir, 'tcx> {}
 pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx> {
     // Foreign function used by linux
@@ -45,7 +67,12 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
             tv_nsec *= sign;
         }
 
-        this.write_c_ints(&tp, &[tv_sec, tv_nsec], &["time_t", "c_long"])?;
+        let imms = [
+            int_to_immty_checked(tv_sec, this.libc_ty_layout("time_t")?)?,
+            int_to_immty_checked(tv_nsec, this.libc_ty_layout("c_long")?)?,
+        ];
+
+        this.write_immediates(&tp, &imms)?;
 
         Ok(0)
     }
@@ -78,7 +105,12 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
             tv_usec *= sign;
         }
 
-        this.write_c_ints(&tv, &[tv_sec, tv_usec], &["time_t", "suseconds_t"])?;
+        let imms = [
+            int_to_immty_checked(tv_sec, this.libc_ty_layout("time_t")?)?,
+            int_to_immty_checked(tv_usec, this.libc_ty_layout("suseconds_t")?)?,
+        ];
+
+        this.write_immediates(&tv, &imms)?;
 
         Ok(0)
     }