bpo-33351: Patches to build on clang-cl

.azure-pipelines/ci.yml

@@ -140,13 +140,21 @@ jobs:
       win32:
         arch: win32
         buildOpt:
+        installClang: no
         testRunTitle: '$(Build.SourceBranchName)-win32'
         testRunPlatform: win32
       win64:
         arch: amd64
         buildOpt: '-p x64'
+        installClang: no
         testRunTitle: '$(Build.SourceBranchName)-win64'
         testRunPlatform: win64
+      win64_clang_cl:
+        arch: amd64
+        buildOpt: '-p x64 "/p:CLToolExe=clang-cl.exe" "/p:CLToolPath=C:\Program Files\LLVM\bin"'
+        installClang: yes
+        testRunTitle: '$(Build.SourceBranchName)-clang_cl-win64'
+        testRunPlatform: win64
     maxParallel: 4
 
   steps:

.azure-pipelines/pr.yml

@@ -140,16 +140,25 @@ jobs:
       win32:
         arch: win32
         buildOpt:
+        installClang: no
         testRunTitle: '$(System.PullRequest.TargetBranch)-win32'
         testRunPlatform: win32
       win64:
         arch: amd64
         buildOpt: '-p x64'
+        installClang: no
         testRunTitle: '$(System.PullRequest.TargetBranch)-win64'
         testRunPlatform: win64
       winarm64:
         arch: arm64
         buildOpt: '-p arm64'
+        installClang: no
+      win64_clang_cl:
+        arch: amd64
+        buildOpt: '-p x64 "/p:CLToolExe=clang-cl.exe" "/p:CLToolPath=C:\Program Files\LLVM\bin"'
+        installClang: yes
+        testRunTitle: '$(Build.SourceBranchName)-clang_cl-win64'
+        testRunPlatform: win64
     maxParallel: 4
 
   steps:

.azure-pipelines/windows-steps.yml

@@ -12,6 +12,18 @@ steps:
     Write-Host '##vso[task.setvariable variable=EXTERNALS_DIR]$(Build.BinariesDirectory)\externals'
   displayName: Update build locations
 
+- powershell: |
+    (New-Object System.Net.WebClient).DownloadFile("https://github.com/llvm/llvm-project/releases/download/llvmorg-9.0.1/LLVM-9.0.1-win32.exe", "LLVM-win.exe")
+    Start-Process .\LLVM-win.exe -ArgumentList '/S' -Wait
+  displayName: Install clang on win32
+  condition: and(eq('yes', variables['installClang']), eq('win32', variables['arch']))
+
+- powershell: |
+    (New-Object System.Net.WebClient).DownloadFile("https://github.com/llvm/llvm-project/releases/download/llvmorg-9.0.1/LLVM-9.0.1-win64.exe", "LLVM-win.exe")
+    Start-Process .\LLVM-win.exe -ArgumentList '/S' -Wait
+  displayName: Install clang on win64
+  condition: and(eq('yes', variables['installClang']), eq('amd64', variables['arch']))
+
 - script: PCbuild\build.bat -e $(buildOpt)
   displayName: 'Build CPython'
   env:

Include/pytime.h

@@ -13,6 +13,12 @@ functions and constants
 extern "C" {
 #endif
 
+#if defined(_MSC_VER)
+        /* Forward declare struct timeval so that clang-cl doesn't complain about it
+        being a local declaration later on  in _PyTime_AsTimeval.*/
+        struct timeval;
+#endif /* _MSC_VER */
+
 /* _PyTime_t: Python timestamp with subsecond precision. It can be used to
    store a duration, and so indirectly a date (related to another date, like
    UNIX epoch). */

Lib/distutils/_msvccompiler.py

@@ -167,6 +167,15 @@ def _find_exe(exe, paths=None):
     'win-arm64' : 'x86_arm64'
 }
 
+# A map keyed by get_platform() return values to value accepted by
+# clang as the triple.
+PLAT_TO_LLVM_TARGETS = {
+    'win32': 'i686-pc-windows-msvc',
+    'win-amd64': 'x86_64-pc-windows-msvc',
+    'win-arm32': 'arm-pc-windows-msvc',
+    'win-arm64': 'aarch64-pc-windows-msvc',
+}
+
 class MSVCCompiler(CCompiler) :
     """Concrete class that implements an interface to Microsoft Visual C++,
        as defined by the CCompiler abstract class."""
@@ -198,11 +207,12 @@ class MSVCCompiler(CCompiler) :
     exe_extension = '.exe'
 
 
-    def __init__(self, verbose=0, dry_run=0, force=0):
+    def __init__(self, verbose=0, dry_run=0, force=0, use_clang_cl=False):
         CCompiler.__init__ (self, verbose, dry_run, force)
         # target platform (.plat_name is consistent with 'bdist')
         self.plat_name = None
         self.initialized = False
+        self.use_clang_cl = use_clang_cl
 
     def initialize(self, plat_name=None):
         # multi-init means we would need to check platform same each time...
@@ -224,7 +234,10 @@ def initialize(self, plat_name=None):
 
         self._paths = vc_env.get('path', '')
         paths = self._paths.split(os.pathsep)
-        self.cc = _find_exe("cl.exe", paths)
+        if self.use_clang_cl:
+            self.cc = _find_exe("clang-cl.exe")
+        else:
+            self.cc = _find_exe("cl.exe", paths)
         self.linker = _find_exe("link.exe", paths)
         self.lib = _find_exe("lib.exe", paths)
         self.rc = _find_exe("rc.exe", paths)   # resource compiler
@@ -258,6 +271,16 @@ def initialize(self, plat_name=None):
         ldflags_debug = [
             '/nologo', '/INCREMENTAL:NO', '/LTCG', '/DEBUG:FULL'
         ]
+        if self.use_clang_cl:
+            # Add target for clang
+            target_flag = "--target=" + PLAT_TO_LLVM_TARGETS[plat_name]
+            self.compile_options.append(target_flag)
+            self.compile_options_debug.append(target_flag)
+            # Remove whole program optimization flags to avoid warnings about
+            # unrecognized options
+            self.compile_options.remove('/GL')
+            ldflags.remove('/LTCG')
+            ldflags_debug.remove('/LTCG')
 
         self.ldflags_exe = [*ldflags, '/MANIFEST:EMBED,ID=1']
         self.ldflags_exe_debug = [*ldflags_debug, '/MANIFEST:EMBED,ID=1']
@@ -537,3 +560,10 @@ def find_library_file(self, dirs, lib, debug=0):
         else:
             # Oops, didn't find it in *any* of 'dirs'
             return None
+
+
+class ClangMSVCCompiler(MSVCCompiler):
+    compiler_type = 'clang-cl'
+
+    def __init__(self, verbose=0, dry_run=0, force=0):
+        MSVCCompiler.__init__(self, verbose, dry_run, force, True)

Lib/distutils/ccompiler.py

@@ -968,6 +968,8 @@ def get_default_compiler(osname=None, platform=None):
                                "Mingw32 port of GNU C Compiler for Win32"),
                    'bcpp':    ('bcppcompiler', 'BCPPCompiler',
                                "Borland C++ Compiler"),
+                   'clang-cl':('_msvccompiler', 'ClangMSVCCompiler',
+                               "clang-cl for Microsoft Visual C++"),
                  }
 
 def show_compilers():

Misc/NEWS.d/next/Build/2018-06-13-03-08-13.bpo-33351.fn4g9Z.rst

@@ -0,0 +1,3 @@
+Port CPython to build with clang-cl on Windows.
+
+Patch by Ethan Smith

Modules/_tracemalloc.c

@@ -52,11 +52,12 @@ static PyThread_type_lock tables_lock;
 
 /* Pack the frame_t structure to reduce the memory footprint on 64-bit
    architectures: 12 bytes instead of 16. */
+#if defined(_MSC_VER)
+#pragma pack(push, 4)
+#endif
 typedef struct
 #ifdef __GNUC__
 __attribute__((packed))
-#elif defined(_MSC_VER)
-#pragma pack(push, 4)
 #endif
 {
     /* filename cannot be NULL: "<unknown>" is used if the Python frame

PC/pyconfig.h

@@ -94,15 +94,9 @@ WIN32 is still required for the locale module.
 /* e.g., this produces, after compile-time string catenation,
  *      ("[MSC v.1200 32 bit (Intel)]")
  *
- * _Py_STRINGIZE(_MSC_VER) expands to
- * _Py_STRINGIZE1((_MSC_VER)) expands to
- * _Py_STRINGIZE2(_MSC_VER) but as this call is the result of token-pasting
- *      it's scanned again for macros and so further expands to (under MSVC 6)
- * _Py_STRINGIZE2(1200) which then expands to
- * "1200"
+ * The double-stringize hack, a method to get the string version of _MSC_VER
  */
-#define _Py_STRINGIZE(X) _Py_STRINGIZE1((X))
-#define _Py_STRINGIZE1(X) _Py_STRINGIZE2 ## X
+#define _Py_STRINGIZE(X) _Py_STRINGIZE2(X)
 #define _Py_STRINGIZE2(X) #X
 
 /* MSVC defines _WINxx to differentiate the windows platform types
@@ -122,6 +116,8 @@ WIN32 is still required for the locale module.
 #if defined(_M_X64) || defined(_M_AMD64)
 #if defined(__INTEL_COMPILER)
 #define COMPILER ("[ICC v." _Py_STRINGIZE(__INTEL_COMPILER) " 64 bit (amd64) with MSC v." _Py_STRINGIZE(_MSC_VER) " CRT]")
+#elif defined(__clang__)
+#define COMPILER ("[clang v." _Py_STRINGIZE(__clang_version__) " 64 bit (amd64) with MSC v." _Py_STRINGIZE(_MSC_VER) " CRT]")
 #else
 #define COMPILER _Py_PASTE_VERSION("64 bit (AMD64)")
 #endif /* __INTEL_COMPILER */
@@ -175,6 +171,8 @@ typedef _W64 int ssize_t;
 #if defined(_M_IX86)
 #if defined(__INTEL_COMPILER)
 #define COMPILER ("[ICC v." _Py_STRINGIZE(__INTEL_COMPILER) " 32 bit (Intel) with MSC v." _Py_STRINGIZE(_MSC_VER) " CRT]")
+#elif defined(__clang__)
+#define COMPILER ("[clang v." _Py_STRINGIZE(__clang_version__) "32 bit (Intel) with MSC v." _Py_STRINGIZE(_MSC_VER) " CRT]")
 #else
 #define COMPILER _Py_PASTE_VERSION("32 bit (Intel)")
 #endif /* __INTEL_COMPILER */