Auto merge of #809 - RalfJung:intptrcast, r=RalfJung

use intptrcast for heap_allocator test; then it should work on Windows

.appveyor.yml

@@ -29,8 +29,6 @@ install:
     - rustc --version
 
 build_script:
-    - set RUST_TEST_NOCAPTURE=1
-    - set RUST_BACKTRACE=1
     - set RUSTFLAGS=-C debug-assertions
     # Build and install miri
     - cargo build --release --all-features --all-targets
@@ -40,6 +38,8 @@ build_script:
     - set MIRI_SYSROOT=%USERPROFILE%\AppData\Local\rust-lang\miri\cache\HOST
 
 test_script:
+    - set RUST_TEST_NOCAPTURE=1
+    - set RUST_BACKTRACE=1
     # Test miri
     - cargo test --release --all-features
     # Test cargo integration

README.md

@@ -333,6 +333,7 @@ Definite bugs found:
 * [Futures turning a shared reference into a mutable one](https://github.com/rust-lang/rust/pull/56319)
 * [`str` turning a shared reference into a mutable one](https://github.com/rust-lang/rust/pull/58200)
 * [`rand` performing unaligned reads](https://github.com/rust-random/rand/issues/779)
+* [The Unix allocator calling `posix_memalign` in an invalid way](https://github.com/rust-lang/rust/issues/62251)
 
 Violations of Stacked Borrows found that are likely bugs (but Stacked Borrows is currently just an experiment):
 

src/intptrcast.rs

@@ -90,6 +90,10 @@ impl<'mir, 'tcx> GlobalState {
                 // From next_base_addr + slack, round up to adjust for alignment.
                 let base_addr = Self::align_addr(global_state.next_base_addr + slack, align.bytes());
                 entry.insert(base_addr);
+                trace!(
+                    "Assigning base address {:#x} to allocation {:?} (slack: {}, align: {})",
+                    base_addr, ptr.alloc_id, slack, align.bytes(),
+                );
 
                 // Remember next base address.  If this allocation is zero-sized, leave a gap
                 // of at least 1 to avoid two allocations having the same base address.

src/shims/foreign_items.rs

@@ -51,6 +51,18 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         Ok(Some(this.load_mir(instance.def)?))
     }
 
+    /// Returns the minimum alignment for the target architecture.
+    fn min_align(&self) -> Align {
+        let this = self.eval_context_ref();
+        // List taken from `libstd/sys_common/alloc.rs`.
+        let min_align = match this.tcx.tcx.sess.target.target.arch.as_str() {
+            "x86" | "arm" | "mips" | "powerpc" | "powerpc64" | "asmjs" | "wasm32" => 8,
+            "x86_64" | "aarch64" | "mips64" | "s390x" | "sparc64" => 16,
+            arch => bug!("Unsupported target architecture: {}", arch),
+        };
+        Align::from_bytes(min_align).unwrap()
+    }
+
     fn malloc(
         &mut self,
         size: u64,
@@ -61,7 +73,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         if size == 0 {
             Scalar::from_int(0, this.pointer_size())
         } else {
-            let align = this.tcx.data_layout.pointer_align.abi;
+            let align = this.min_align();
             let ptr = this.memory_mut().allocate(Size::from_bytes(size), align, MiriMemoryKind::C.into());
             if zero_init {
                 // We just allocated this, the access cannot fail
@@ -94,7 +106,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         new_size: u64,
     ) -> InterpResult<'tcx, Scalar<Tag>> {
         let this = self.eval_context_mut();
-        let align = this.tcx.data_layout.pointer_align.abi;
+        let align = this.min_align();
         if old_ptr.is_null_ptr(this) {
             if new_size == 0 {
                 Ok(Scalar::from_int(0, this.pointer_size()))
@@ -191,12 +203,16 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 if !align.is_power_of_two() {
                     return err!(HeapAllocNonPowerOfTwoAlignment(align));
                 }
+                /*
+                FIXME: This check is disabled because rustc violates it.
+                See <https://github.com/rust-lang/rust/issues/62251>.
                 if align < this.pointer_size().bytes() {
                     return err!(MachineError(format!(
                         "posix_memalign: alignment must be at least the size of a pointer, but is {}",
                         align,
                     )));
                 }
+                */
                 if size == 0 {
                     this.write_null(ret.into())?;
                 } else {

tests/run-pass/heap_allocator.rs

@@ -1,51 +1,64 @@
+// compile-flags: -Zmiri-seed=
 #![feature(allocator_api)]
 
 use std::ptr::NonNull;
 use std::alloc::{Global, Alloc, Layout, System};
 use std::slice;
 
 fn check_alloc<T: Alloc>(mut allocator: T) { unsafe {
-    let layout = Layout::from_size_align(20, 4).unwrap();
-    let a = allocator.alloc(layout).unwrap();
-    allocator.dealloc(a, layout);
+    for &align in &[4, 8, 16, 32] {
+        let layout = Layout::from_size_align(20, align).unwrap();
 
-    let p1 = allocator.alloc_zeroed(layout).unwrap();
+        for _ in 0..32 {
+            let a = allocator.alloc(layout).unwrap();
+            assert_eq!(a.as_ptr() as usize % align, 0, "pointer is incorrectly aligned");
+            allocator.dealloc(a, layout);
+        }
+
+        let p1 = allocator.alloc_zeroed(layout).unwrap();
+        assert_eq!(p1.as_ptr() as usize % align, 0, "pointer is incorrectly aligned");
 
-    let p2 = allocator.realloc(p1, Layout::from_size_align(20, 4).unwrap(), 40).unwrap();
-    let slice = slice::from_raw_parts(p2.as_ptr(), 20);
-    assert_eq!(&slice, &[0_u8; 20]);
+        let p2 = allocator.realloc(p1, layout, 40).unwrap();
+        let layout = Layout::from_size_align(40, align).unwrap();
+        assert_eq!(p2.as_ptr() as usize % align, 0, "pointer is incorrectly aligned");
+        let slice = slice::from_raw_parts(p2.as_ptr(), 20);
+        assert_eq!(&slice, &[0_u8; 20]);
 
-    // old size == new size
-    let p3 = allocator.realloc(p2, Layout::from_size_align(40, 4).unwrap(), 40).unwrap();
-    let slice = slice::from_raw_parts(p3.as_ptr(), 20);
-    assert_eq!(&slice, &[0_u8; 20]);
+        // old size == new size
+        let p3 = allocator.realloc(p2, layout, 40).unwrap();
+        assert_eq!(p3.as_ptr() as usize % align, 0, "pointer is incorrectly aligned");
+        let slice = slice::from_raw_parts(p3.as_ptr(), 20);
+        assert_eq!(&slice, &[0_u8; 20]);
 
-    // old size > new size
-    let p4 = allocator.realloc(p3, Layout::from_size_align(40, 4).unwrap(), 10).unwrap();
-    let slice = slice::from_raw_parts(p4.as_ptr(), 10);
-    assert_eq!(&slice, &[0_u8; 10]);
+        // old size > new size
+        let p4 = allocator.realloc(p3, layout, 10).unwrap();
+        let layout = Layout::from_size_align(10, align).unwrap();
+        assert_eq!(p4.as_ptr() as usize % align, 0, "pointer is incorrectly aligned");
+        let slice = slice::from_raw_parts(p4.as_ptr(), 10);
+        assert_eq!(&slice, &[0_u8; 10]);
 
-    allocator.dealloc(p4, Layout::from_size_align(10, 4).unwrap());
+        allocator.dealloc(p4, layout);
+    }
 } }
 
 fn check_overalign_requests<T: Alloc>(mut allocator: T) {
-    let size = 8;
-    // Greater than `size`.
-    let align = 16;
-    // Miri is deterministic; no need to try many times.
-    let iterations = 1;
-    unsafe {
-        let pointers: Vec<_> = (0..iterations).map(|_| {
-            allocator.alloc(Layout::from_size_align(size, align).unwrap()).unwrap()
-        }).collect();
-        for &ptr in &pointers {
-            assert_eq!((ptr.as_ptr() as usize) % align, 0,
-                       "Got a pointer less aligned than requested")
-        }
+    for &size in &[2, 8, 64] { // size less than and bigger than alignment
+        for &align in &[4, 8, 16, 32] { // Be sure to cover less than and bigger than `MIN_ALIGN` for all architectures
+            let iterations = 32;
+            unsafe {
+                let pointers: Vec<_> = (0..iterations).map(|_| {
+                    allocator.alloc(Layout::from_size_align(size, align).unwrap()).unwrap()
+                }).collect();
+                for &ptr in &pointers {
+                    assert_eq!((ptr.as_ptr() as usize) % align, 0,
+                            "Got a pointer less aligned than requested")
+                }
 
-        // Clean up.
-        for &ptr in &pointers {
-            allocator.dealloc(ptr, Layout::from_size_align(size, align).unwrap())
+                // Clean up.
+                for &ptr in &pointers {
+                    allocator.dealloc(ptr, Layout::from_size_align(size, align).unwrap())
+                }
+            }
         }
     }
 }
@@ -75,7 +88,6 @@ fn box_to_global() {
 fn main() {
     check_alloc(System);
     check_alloc(Global);
-    #[cfg(not(target_os = "windows"))] // TODO: Inspects allocation base address on Windows; needs intptrcast model
     check_overalign_requests(System);
     check_overalign_requests(Global);
     global_to_box();