Rollup of 11 pull requests

src/bootstrap/bin/rustc.rs

@@ -181,6 +181,33 @@ fn main() {
             cmd.arg("-C").arg(format!("debug-assertions={}", debug_assertions));
         }
 
+        // Build all crates in the `std` facade with `-Z emit-stack-sizes` to add stack usage
+        // information.
+        //
+        // When you use this `-Z` flag with Cargo you get stack usage information on all crates
+        // compiled from source, and when you are using LTO you also get information on pre-compiled
+        // crates like `core` and `std`, even if they were not compiled with `-Z emit-stack-sizes`.
+        // However, there's an exception: `compiler_builtins`. This crate is special and doesn't
+        // participate in LTO because it's always linked as a separate object file. For this reason
+        // it's impossible to get stack usage information about `compiler-builtins` using
+        // `RUSTFLAGS` + Cargo, or `cargo rustc`.
+        //
+        // To make the stack usage information of all crates under the `std` facade available to
+        // Cargo based stack usage analysis tools, in both LTO and non-LTO mode, we compile them
+        // with the `-Z emit-stack-sizes` flag. The `RUSTC_EMIT_STACK_SIZES` var helps us apply this
+        // flag only to the crates in the `std` facade. The `-Z` flag is known to currently work
+        // with targets that produce ELF files so we limit its use flag to those targets.
+        //
+        // NOTE(japaric) if this ever causes problem with an LLVM upgrade or any PR feel free to
+        // remove it or comment it out
+        if env::var_os("RUSTC_EMIT_STACK_SIZES").is_some()
+            && (target.contains("-linux-")
+                || target.contains("-none-eabi")
+                || target.ends_with("-none-elf"))
+        {
+            cmd.arg("-Zemit-stack-sizes");
+        }
+
         if let Ok(s) = env::var("RUSTC_CODEGEN_UNITS") {
             cmd.arg("-C").arg(format!("codegen-units={}", s));
         }

src/bootstrap/compile.rs

@@ -97,6 +97,8 @@ impl Step for Std {
         let _folder = builder.fold_output(|| format!("stage{}-std", compiler.stage));
         builder.info(&format!("Building stage{} std artifacts ({} -> {})", compiler.stage,
                 &compiler.host, target));
+        // compile with `-Z emit-stack-sizes`; see bootstrap/src/rustc.rs for more details
+        cargo.env("RUSTC_EMIT_STACK_SIZES", "1");
         run_cargo(builder,
                   &mut cargo,
                   &libstd_stamp(builder, compiler, target),
@@ -382,6 +384,8 @@ impl Step for Test {
         let _folder = builder.fold_output(|| format!("stage{}-test", compiler.stage));
         builder.info(&format!("Building stage{} test artifacts ({} -> {})", compiler.stage,
                 &compiler.host, target));
+        // compile with `-Z emit-stack-sizes`; see bootstrap/src/rustc.rs for more details
+        cargo.env("RUSTC_EMIT_STACK_SIZES", "1");
         run_cargo(builder,
                   &mut cargo,
                   &libtest_stamp(builder, compiler, target),

src/ci/docker/scripts/musl-toolchain.sh

@@ -29,6 +29,10 @@ TARGET=$ARCH-linux-musl
 OUTPUT=/usr/local
 shift
 
+# Ancient binutils versions don't understand debug symbols produced by more recent tools.
+# Apparently applying `-fPIC` everywhere allows them to link successfully.
+export CFLAGS="-fPIC $CFLAGS"
+
 git clone https://github.com/richfelker/musl-cross-make -b v0.9.7
 cd musl-cross-make
 

src/librustc/lint/builtin.rs

@@ -354,7 +354,7 @@ declare_lint! {
 
 declare_lint! {
     pub DUPLICATE_MATCHER_BINDING_NAME,
-    Warn,
+    Deny,
     "duplicate macro matcher binding name"
 }
 
@@ -464,6 +464,7 @@ impl LintPass for HardwiredLints {
             DEPRECATED_IN_FUTURE,
             AMBIGUOUS_ASSOCIATED_ITEMS,
             NESTED_IMPL_TRAIT,
+            DUPLICATE_MATCHER_BINDING_NAME,
         )
     }
 }