Sort the fat LTO modules to produce deterministic output.

src/librustc_codegen_llvm/back/lto.rs

@@ -265,7 +265,7 @@ fn fat_lto(cgcx: &CodegenContext<LlvmCodegenBackend>,
         // and we want to move everything to the same LLVM context. Currently the
         // way we know of to do that is to serialize them to a string and them parse
         // them later. Not great but hey, that's why it's "fat" LTO, right?
-        serialized_modules.extend(modules.into_iter().map(|module| {
+        let mut new_modules = modules.into_iter().map(|module| {
             match module {
                 FatLTOInput::InMemory(module) => {
                     let buffer = ModuleBuffer::new(module.module_llvm.llmod());
@@ -277,7 +277,10 @@ fn fat_lto(cgcx: &CodegenContext<LlvmCodegenBackend>,
                     (SerializedModule::Local(buffer), llmod_id)
                 }
             }
-        }));
+        }).collect::<Vec<_>>();
+        // Sort the modules to ensure we produce deterministic results.
+        new_modules.sort_by(|module1, module2| module1.1.partial_cmp(&module2.1).unwrap());
+        serialized_modules.extend(new_modules);
         serialized_modules.extend(cached_modules.into_iter().map(|(buffer, wp)| {
             (buffer, CString::new(wp.cgu_name).unwrap())
         }));

src/test/run-make-fulldeps/reproducible-build-2/Makefile

@@ -0,0 +1,16 @@
+-include ../tools.mk
+
+# ignore-musl
+# ignore-windows
+# Objects are reproducible but their path is not.
+
+all:  \
+	fat_lto
+
+fat_lto:
+	rm -rf $(TMPDIR) && mkdir $(TMPDIR)
+	$(RUSTC) reproducible-build-aux.rs
+	$(RUSTC) reproducible-build.rs -C lto=fat
+	cp $(TMPDIR)/reproducible-build $(TMPDIR)/reproducible-build-a
+	$(RUSTC) reproducible-build.rs -C lto=fat
+	cmp "$(TMPDIR)/reproducible-build-a" "$(TMPDIR)/reproducible-build" || exit 1

src/test/run-make-fulldeps/reproducible-build-2/linker.rs

@@ -0,0 +1,44 @@
+use std::env;
+use std::path::Path;
+use std::fs::File;
+use std::io::{Read, Write};
+
+fn main() {
+    let mut dst = env::current_exe().unwrap();
+    dst.pop();
+    dst.push("linker-arguments1");
+    if dst.exists() {
+        dst.pop();
+        dst.push("linker-arguments2");
+        assert!(!dst.exists());
+    }
+
+    let mut out = String::new();
+    for arg in env::args().skip(1) {
+        let path = Path::new(&arg);
+        if !path.is_file() {
+            out.push_str(&arg);
+            out.push_str("\n");
+            continue
+        }
+
+        let mut contents = Vec::new();
+        File::open(path).unwrap().read_to_end(&mut contents).unwrap();
+
+        out.push_str(&format!("{}: {}\n", arg, hash(&contents)));
+    }
+
+    File::create(dst).unwrap().write_all(out.as_bytes()).unwrap();
+}
+
+// fnv hash for now
+fn hash(contents: &[u8]) -> u64 {
+    let mut hash = 0xcbf29ce484222325;
+
+    for byte in contents {
+        hash = hash ^ (*byte as u64);
+        hash = hash.wrapping_mul(0x100000001b3);
+    }
+
+    hash
+}

src/test/run-make-fulldeps/reproducible-build-2/reproducible-build-aux.rs

@@ -0,0 +1,28 @@
+#![crate_type="lib"]
+
+pub static STATIC: i32 = 1234;
+
+pub struct Struct<T1, T2> {
+    _t1: std::marker::PhantomData<T1>,
+    _t2: std::marker::PhantomData<T2>,
+}
+
+pub fn regular_fn(_: i32) {}
+
+pub fn generic_fn<T1, T2>() {}
+
+impl<T1, T2> Drop for Struct<T1, T2> {
+    fn drop(&mut self) {}
+}
+
+pub enum Enum {
+    Variant1,
+    Variant2(u32),
+    Variant3 { x: u32 }
+}
+
+pub struct TupleStruct(pub i8, pub i16, pub i32, pub i64);
+
+pub trait Trait<T1, T2> {
+    fn foo(&self);
+}

src/test/run-make-fulldeps/reproducible-build-2/reproducible-build.rs

@@ -0,0 +1,116 @@
+// This test case makes sure that two identical invocations of the compiler
+// (i.e., same code base, same compile-flags, same compiler-versions, etc.)
+// produce the same output. In the past, symbol names of monomorphized functions
+// were not deterministic (which we want to avoid).
+//
+// The test tries to exercise as many different paths into symbol name
+// generation as possible:
+//
+// - regular functions
+// - generic functions
+// - methods
+// - statics
+// - closures
+// - enum variant constructors
+// - tuple struct constructors
+// - drop glue
+// - FnOnce adapters
+// - Trait object shims
+// - Fn Pointer shims
+
+#![allow(dead_code, warnings)]
+
+extern crate reproducible_build_aux;
+
+static STATIC: i32 = 1234;
+
+pub struct Struct<T1, T2> {
+    x: T1,
+    y: T2,
+}
+
+fn regular_fn(_: i32) {}
+
+fn generic_fn<T1, T2>() {}
+
+impl<T1, T2> Drop for Struct<T1, T2> {
+    fn drop(&mut self) {}
+}
+
+pub enum Enum {
+    Variant1,
+    Variant2(u32),
+    Variant3 { x: u32 }
+}
+
+struct TupleStruct(i8, i16, i32, i64);
+
+impl TupleStruct {
+    pub fn bar(&self) {}
+}
+
+trait Trait<T1, T2> {
+    fn foo(&self);
+}
+
+impl Trait<i32, u64> for u64 {
+    fn foo(&self) {}
+}
+
+impl reproducible_build_aux::Trait<char, String> for TupleStruct {
+    fn foo(&self) {}
+}
+
+fn main() {
+    regular_fn(STATIC);
+    generic_fn::<u32, char>();
+    generic_fn::<char, Struct<u32, u64>>();
+    generic_fn::<Struct<u64, u32>, reproducible_build_aux::Struct<u32, u64>>();
+
+    let dropped = Struct {
+        x: "",
+        y: 'a',
+    };
+
+    let _ = Enum::Variant1;
+    let _ = Enum::Variant2(0);
+    let _ = Enum::Variant3 { x: 0 };
+    let _ = TupleStruct(1, 2, 3, 4);
+
+    let closure  = |x| {
+        x + 1i32
+    };
+
+    fn inner<F: Fn(i32) -> i32>(f: F) -> i32 {
+        f(STATIC)
+    }
+
+    println!("{}", inner(closure));
+
+    let object_shim: &Trait<i32, u64> = &0u64;
+    object_shim.foo();
+
+    fn with_fn_once_adapter<F: FnOnce(i32)>(f: F) {
+        f(0);
+    }
+
+    with_fn_once_adapter(|_:i32| { });
+
+    reproducible_build_aux::regular_fn(STATIC);
+    reproducible_build_aux::generic_fn::<u32, char>();
+    reproducible_build_aux::generic_fn::<char, Struct<u32, u64>>();
+    reproducible_build_aux::generic_fn::<Struct<u64, u32>,
+                                         reproducible_build_aux::Struct<u32, u64>>();
+
+    let _ = reproducible_build_aux::Enum::Variant1;
+    let _ = reproducible_build_aux::Enum::Variant2(0);
+    let _ = reproducible_build_aux::Enum::Variant3 { x: 0 };
+    let _ = reproducible_build_aux::TupleStruct(1, 2, 3, 4);
+
+    let object_shim: &reproducible_build_aux::Trait<char, String> = &TupleStruct(0, 1, 2, 3);
+    object_shim.foo();
+
+    let pointer_shim: &Fn(i32) = &regular_fn;
+
+    TupleStruct(1, 2, 3, 4).bar();
+}