From 948e60454a9ada5b223e8f9ea8b2c4a0ccfd6647 Mon Sep 17 00:00:00 2001
From: Simonas Kazlauskas <git@kazlauskas.me>
Date: Wed, 18 Aug 2021 13:12:10 +0300
Subject: [PATCH 1/2] Attempt to fix-up clang-cl support

If the user specifies `CC=...` then the previous fallback to `clang`
would fail to work if `clang` wasn't in the path. This is quite likely
on Windows in particular.

Lets just drop the use of preprocessor on Windows and directly code the
one constant that the preprocessor was handling.
---
 psm/build.rs                      | 46 ++++++++++++-------------------
 psm/src/arch/x86_64_windows_gnu.s |  4 +--
 psm/src/arch/x86_windows_gnu.s    |  5 +---
 3 files changed, 20 insertions(+), 35 deletions(-)

diff --git a/psm/build.rs b/psm/build.rs
index 60e89f6..07baeb8 100644
--- a/psm/build.rs
+++ b/psm/build.rs
@@ -73,38 +73,28 @@ fn main() {
     }
 
     let mut cfg = cc::Build::new();
-    // There seems to be a bug with clang-cl where using
-    // `/clang:-xassembler-with-cpp` is apparently accepted (ie no warnings
-    // about unused/unknown arguments), but results in the same exact error
-    // as if the flag was not present, so instead we take advantage of the
-    // fact that we're not actually compiling any C/C++ code, only assembling
-    // and can just use clang directly.
-    if cfg
+    let msvc = cfg.get_compiler().is_like_msvc();
+    let clang_cl = cfg
         .get_compiler()
         .path()
         .file_name()
         .and_then(|f| f.to_str())
-        .map(|fname| fname.contains("clang-cl"))
-        .unwrap_or(false)
-    {
-        cfg.compiler("clang");
-    }
-
-    let msvc = cfg.get_compiler().is_like_msvc();
-    let asm =
-        if let Some((asm, canswitch)) = find_assembly(&arch, &endian, &os, &env, msvc) {
-            println!("cargo:rustc-cfg=asm");
-            if canswitch {
-                println!("cargo:rustc-cfg=switchable_stack")
-            }
-            asm
-        } else {
-            println!(
-                "cargo:warning=Target {}-{}-{} has no assembly files!",
-                arch, os, env
-            );
-            return;
-        };
+        .map(|f| f.contains("clang-cl"))
+        .unwrap_or(false);
+    let masm = msvc && !clang_cl;
+    let asm = if let Some((asm, canswitch)) = find_assembly(&arch, &endian, &os, &env, masm) {
+        println!("cargo:rustc-cfg=asm");
+        if canswitch {
+            println!("cargo:rustc-cfg=switchable_stack")
+        }
+        asm
+    } else {
+        println!(
+            "cargo:warning=Target {}-{}-{} has no assembly files!",
+            arch, os, env
+        );
+        return;
+    };
 
     if !msvc {
         cfg.flag("-xassembler-with-cpp");
diff --git a/psm/src/arch/x86_64_windows_gnu.s b/psm/src/arch/x86_64_windows_gnu.s
index 37c9e1c..8f12583 100644
--- a/psm/src/arch/x86_64_windows_gnu.s
+++ b/psm/src/arch/x86_64_windows_gnu.s
@@ -1,5 +1,3 @@
-#include "psm.h"
-
 .text
 
 .def rust_psm_stack_direction
@@ -11,7 +9,7 @@
 rust_psm_stack_direction:
 /* extern "sysv64" fn() -> u8 (%al) */
 .cfi_startproc
-    movb $STACK_DIRECTION_DESCENDING, %al # always descending on x86_64
+    movb $2, %al # always descending on x86_64
     retq
 .cfi_endproc
 
diff --git a/psm/src/arch/x86_windows_gnu.s b/psm/src/arch/x86_windows_gnu.s
index cf7f483..474d416 100644
--- a/psm/src/arch/x86_windows_gnu.s
+++ b/psm/src/arch/x86_windows_gnu.s
@@ -1,8 +1,5 @@
 /* FIXME: this works locally but not on appveyor??!? */
-
-#include "psm.h"
 /* NOTE: fastcall calling convention used on all x86 targets */
-
 .text
 
 .def @rust_psm_stack_direction@0
@@ -14,7 +11,7 @@
 @rust_psm_stack_direction@0:
 /* extern "fastcall" fn() -> u8 (%al) */
 .cfi_startproc
-    movb $STACK_DIRECTION_DESCENDING, %al # always descending on x86_64
+    movb $2, %al # always descending on x86_64
     retl
 .cfi_endproc
 

From 01c77f5036aa9be32beeada46e846465d2644526 Mon Sep 17 00:00:00 2001
From: Simonas Kazlauskas <git@kazlauskas.me>
Date: Wed, 18 Aug 2021 13:21:15 +0300
Subject: [PATCH 2/2] Add clang-cl test, maybe?

---
 .github/workflows/test.yml | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 27dca96..a5c045c 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -46,6 +46,36 @@ jobs:
           command: test
           args: --manifest-path=${{ matrix.manifest }} ${{ matrix.mode }} --examples -- --nocapture
 
+  clang-cl-test:
+    name: Test ${{ matrix.manifest }} on ${{ matrix.rust_target }} with ${{ matrix.clang_cl }}
+    runs-on: windows-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        manifest: ['psm/Cargo.toml', 'Cargo.toml']
+        rust_target:
+          - x86_64-pc-windows-msvc
+          - i686-pc-windows-msvc
+        include:
+          - rust_target: x86_64-pc-windows-msvc
+            clang_cl: C:/msys64/mingw64/bin/clang-cl.exe
+          - rust_target: i686-pc-windows-msvc
+            clang_cl: C:/msys64/mingw32/bin/clang-cl.exe
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions-rs/toolchain@v1
+        with:
+            toolchain: stable
+            profile: minimal
+            default: true
+            target: ${{ matrix.rust_target }}
+      - uses: actions-rs/cargo@v1
+        with:
+          command: test
+          args: --manifest-path=${{ matrix.manifest }} -- --nocapture
+        env:
+          CC: ${{ matrix.clang_cl }}
+
   windows-gnu-test:
     name: Test ${{ matrix.manifest }} on ${{ matrix.rust_target }} with ${{ matrix.rust_toolchain }}
     runs-on: windows-latest