[release/6.0] Fix build with Clang 13 (#63314)

* Fix clang 13 induced runtime issues (#62170)

The clang 13 optimizer started to assume that "this" pointer is always
properly aligned. That lead to elimination of some code that was actually
needed.
It also takes pointer aliasing rules more strictly in one place in jit.
That caused the optimizer to falsely assume that a callee with an argument
passed by reference is not modifying that argument and used a stale
copy of the original value at the caller site.

This change fixes both of the issues. With this fix, runtime compiled
using clang 13 seems to be fully functional.

* Fix build with clang 13 (#60328)

eng/native/configurecompiler.cmake

@@ -340,15 +340,17 @@ if (CLR_CMAKE_HOST_UNIX)
   #These seem to indicate real issues
   add_compile_options($<$<COMPILE_LANGUAGE:CXX>:-Wno-invalid-offsetof>)
 
-  if (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
+  add_compile_options(-Wno-unused-but-set-variable)
+
+  if (CMAKE_C_COMPILER_ID MATCHES "Clang")
+    add_compile_options(-Wno-unknown-warning-option)
+
     # The -ferror-limit is helpful during the porting, it makes sure the compiler doesn't stop
     # after hitting just about 20 errors.
     add_compile_options(-ferror-limit=4096)
 
     # Disabled warnings
     add_compile_options(-Wno-unused-private-field)
-    # Explicit constructor calls are not supported by clang (this->ClassName::ClassName())
-    add_compile_options(-Wno-microsoft)
     # There are constants of type BOOL used in a condition. But BOOL is defined as int
     # and so the compiler thinks that there is a mistake.
     add_compile_options(-Wno-constant-logical-operand)
@@ -363,8 +365,9 @@ if (CLR_CMAKE_HOST_UNIX)
     # to a struct or a class that has virtual members or a base class. In that case, clang
     # may not generate the same object layout as MSVC.
     add_compile_options(-Wno-incompatible-ms-struct)
+
+    add_compile_options(-Wno-reserved-identifier)
   else()
-    add_compile_options(-Wno-unused-but-set-variable)
     add_compile_options(-Wno-unknown-pragmas)
     add_compile_options(-Wno-uninitialized)
     add_compile_options(-Wno-strict-aliasing)

src/coreclr/inc/corhlpr.h

@@ -336,7 +336,7 @@ struct COR_ILMETHOD_SECT
     const COR_ILMETHOD_SECT* Next() const
     {
         if (!More()) return(0);
-        return ((COR_ILMETHOD_SECT*)(((BYTE *)this) + DataSize()))->Align();
+        return ((COR_ILMETHOD_SECT*)Align(((BYTE *)this) + DataSize()));
     }
 
     const BYTE* Data() const
@@ -374,9 +374,9 @@ struct COR_ILMETHOD_SECT
         return((AsSmall()->Kind & CorILMethod_Sect_FatFormat) != 0);
     }
 
-    const COR_ILMETHOD_SECT* Align() const
+    static const void* Align(const void* p)
     {
-        return((COR_ILMETHOD_SECT*) ((((UINT_PTR) this) + 3) & ~3));
+        return((void*) ((((UINT_PTR) p) + 3) & ~3));
     }
 
 protected:
@@ -579,7 +579,7 @@ typedef struct tagCOR_ILMETHOD_FAT : IMAGE_COR_ILMETHOD_FAT
 
     const COR_ILMETHOD_SECT* GetSect() const {
         if (!More()) return (0);
-        return(((COR_ILMETHOD_SECT*) (GetCode() + GetCodeSize()))->Align());
+        return(((COR_ILMETHOD_SECT*) COR_ILMETHOD_SECT::Align(GetCode() + GetCodeSize())));
     }
 } COR_ILMETHOD_FAT;
 

src/coreclr/jit/bitsetasshortlong.h

@@ -345,7 +345,7 @@ class BitSetOps</*BitSetType*/ BitSetShortLongRep,
     {
         if (IsShort(env))
         {
-            (size_t&)out = (size_t)out & ((size_t)gen | (size_t)in);
+            out = (BitSetShortLongRep)((size_t)out & ((size_t)gen | (size_t)in));
         }
         else
         {
@@ -361,7 +361,7 @@ class BitSetOps</*BitSetType*/ BitSetShortLongRep,
     {
         if (IsShort(env))
         {
-            (size_t&)in = (size_t)use | ((size_t)out & ~(size_t)def);
+            in = (BitSetShortLongRep)((size_t)use | ((size_t)out & ~(size_t)def));
         }
         else
         {

src/coreclr/jit/inlinepolicy.h

@@ -185,7 +185,7 @@ class DefaultPolicy : public LegalPolicy
 class ExtendedDefaultPolicy : public DefaultPolicy
 {
 public:
-    ExtendedDefaultPolicy::ExtendedDefaultPolicy(Compiler* compiler, bool isPrejitRoot)
+    ExtendedDefaultPolicy(Compiler* compiler, bool isPrejitRoot)
         : DefaultPolicy(compiler, isPrejitRoot)
         , m_ProfileFrequency(0.0)
         , m_BinaryExprWithCns(0)

src/libraries/Native/Unix/CMakeLists.txt

@@ -36,6 +36,8 @@ add_compile_options(-Wno-cast-align)
 add_compile_options(-Wno-typedef-redefinition)
 add_compile_options(-Wno-c11-extensions)
 add_compile_options(-Wno-unknown-pragmas)
+add_compile_options(-Wno-unknown-warning-option)
+add_compile_options(-Wno-unused-but-set-variable)
 
 check_c_compiler_flag(-Wimplicit-fallthrough COMPILER_SUPPORTS_W_IMPLICIT_FALLTHROUGH)
 if (COMPILER_SUPPORTS_W_IMPLICIT_FALLTHROUGH)
@@ -48,6 +50,7 @@ add_compile_options(-g)
 if(CMAKE_C_COMPILER_ID STREQUAL Clang)
     add_compile_options(-Wthread-safety)
     add_compile_options(-Wno-thread-safety-analysis)
+    add_compile_options(-Wno-reserved-identifier)
 elseif(CMAKE_C_COMPILER_ID STREQUAL GNU)
     add_compile_options(-Wno-stringop-truncation)
 endif()

src/libraries/Native/Unix/System.Native/pal_process.c

@@ -191,6 +191,24 @@ static int SetGroups(uint32_t* userGroups, int32_t userGroupsLength, uint32_t* p
     return rv;
 }
 
+typedef void (*VoidIntFn)(int);
+
+static
+VoidIntFn
+handler_from_sigaction (struct sigaction *sa)
+{
+    if (((unsigned int)sa->sa_flags) & SA_SIGINFO)
+    {
+        // work around -Wcast-function-type
+        void (*tmp)(void) = (void (*)(void))sa->sa_sigaction;
+        return (void (*)(int))tmp;
+    }
+    else
+    {
+        return sa->sa_handler;
+    }
+}
+
 int32_t SystemNative_ForkAndExecProcess(const char* filename,
                                       char* const argv[],
                                       char* const envp[],
@@ -371,7 +389,7 @@ int32_t SystemNative_ForkAndExecProcess(const char* filename,
             }
             if (!sigaction(sig, NULL, &sa_old))
             {
-                void (*oldhandler)(int) = (((unsigned int)sa_old.sa_flags) & SA_SIGINFO) ? (void (*)(int))sa_old.sa_sigaction : sa_old.sa_handler;
+                void (*oldhandler)(int) = handler_from_sigaction (&sa_old);
                 if (oldhandler != SIG_IGN && oldhandler != SIG_DFL)
                 {
                     // It has a custom handler, put the default handler back.