Parts of libcompiler_builtins are compiled as WX

[djc]

Similar to rust-lang/rust#34482, I still see a number of warnings like this when compiling rust-1.19.0:

 * !WX --- --- usr/lib64/rustlib/x86_64-unknown-linux-gnu/lib/libcompiler_builtins-701380125126dfef.rlib:chkstk.o
 * !WX --- --- usr/lib64/rustlib/x86_64-unknown-linux-gnu/lib/libcompiler_builtins-701380125126dfef.rlib:chkstk2.o
 * !WX --- --- usr/lib64/rustlib/x86_64-unknown-linux-gnu/lib/libcompiler_builtins-701380125126dfef.rlib:floatundidf.o
 * !WX --- --- usr/lib64/rustlib/x86_64-unknown-linux-gnu/lib/libcompiler_builtins-701380125126dfef.rlib:floatundisf.o
 * !WX --- --- usr/lib64/rustlib/x86_64-unknown-linux-gnu/lib/libcompiler_builtins-701380125126dfef.rlib:floatundixf.o

[alexcrichton]

Oh dear definitely seems like something to fix! @djc would you be up for submitting a patch for at least the easy piece, removing compilation of chkstk files on non-windows platforms?

[djc]

Uh, I guess. Do you mean like this?

diff --git a/build.rs b/build.rs
index 25cc520..787906f 100644
--- a/build.rs
+++ b/build.rs
@@ -4172,8 +4172,6 @@ mod c {
                     &[
                         "i386/ashldi3.S",
                         "i386/ashrdi3.S",
-                        "i386/chkstk.S",
-                        "i386/chkstk2.S",
                         "i386/divdi3.S",
                         "i386/floatdidf.S",
                         "i386/floatdisf.S",
@@ -4188,6 +4186,14 @@ mod c {
                         "i386/umoddi3.S",
                     ],
                 );
+                if target_os == "windows" {
+                    sources.extend(
+                        &[
+                            "i386/chkstk.S",
+                            "i386/chkstk2.S",
+                        ],
+                    );
+                }
             }
         }

[alexcrichton]

I think that should do it yeah!

If you'd like as well, it'd be awesome to add a test into this repo to ensure that we don't regress this.

[djc]

I have no clue how I'd test that, but if you can guide me along maybe I can come up with something.

[alexcrichton]

Right now the test script is just a shell script and has a few other examples, could that be added to?

[DimitryAndric]

Indeed, those files should only be built for Windows. See also llvm-mirror/compiler-rt@1955731

[tgross35]

I don't believe this is an issue anymore, so I'm just attempting to add an object file check that this doesn't regress #934. However, I am not exactly clear on the logic here - @djc (or anyone) do you happen to know what scanelf is actually looking for, or what we should be trying to find? From the source it looks like scanelf finding object files without .note.GNU-stack , which is what I implemented, but there must be some more logic because I can't seem to create an object file that emits !WX locally.