[clang] fb88297 - [clang] Disallow mixing SEH and Objective-C exceptions

[Nico Weber via cfe-commits]

Author: Nico Weber
Date: 2021-10-20T14:18:12-04:00
New Revision: fb8829768d774689c368c49cb3ca17339378cd91

URL: https://github.com/llvm/llvm-project/commit/fb8829768d774689c368c49cb3ca17339378cd91
DIFF: https://github.com/llvm/llvm-project/commit/fb8829768d774689c368c49cb3ca17339378cd91.diff

LOG: [clang] Disallow mixing SEH and Objective-C exceptions

We already disallow mixing SEH and C++ exceptions, and
mixing SEH and Objective-C exceptions seems to not work (see PR52233).
Emitting an error is friendlier than crashing.

Differential Revision: https://reviews.llvm.org/D112157

Added: 
    clang/test/SemaCXX/exceptions-seh.mm

Modified: 
    clang/include/clang/Basic/DiagnosticSemaKinds.td
    clang/include/clang/Sema/ScopeInfo.h
    clang/lib/Sema/ScopeInfo.cpp
    clang/lib/Sema/SemaStmt.cpp

Removed: 
    


################################################################################
diff  --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index e0c36961a9124..13f8fc3de03ca 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -7516,7 +7516,8 @@ def note_throw_in_function : Note<"function declared non-throwing here">;
 def err_seh_try_outside_functions : Error<
   "cannot use SEH '__try' in blocks, captured regions, or Obj-C method decls">;
 def err_mixing_cxx_try_seh_try : Error<
-  "cannot use C++ 'try' in the same function as SEH '__try'">;
+  "cannot use %select{C++ 'try'|Objective-C '@try'}0 "
+  "in the same function as SEH '__try'">;
 def err_seh_try_unsupported : Error<
   "SEH '__try' is not supported on this target">;
 def note_conflicting_try_here : Note<

diff  --git a/clang/include/clang/Sema/ScopeInfo.h b/clang/include/clang/Sema/ScopeInfo.h
index 5c3bfe7e80cdc..ccd15ea6a818f 100644
--- a/clang/include/clang/Sema/ScopeInfo.h
+++ b/clang/include/clang/Sema/ScopeInfo.h
@@ -175,8 +175,9 @@ class FunctionScopeInfo {
   /// First 'return' statement in the current function.
   SourceLocation FirstReturnLoc;
 
-  /// First C++ 'try' statement in the current function.
-  SourceLocation FirstCXXTryLoc;
+  /// First C++ 'try' or ObjC @try statement in the current function.
+  SourceLocation FirstCXXOrObjCTryLoc;
+  enum { TryLocIsCXX, TryLocIsObjC, Unknown } FirstTryType = Unknown;
 
   /// First SEH '__try' statement in the current function.
   SourceLocation FirstSEHTryLoc;
@@ -446,7 +447,14 @@ class FunctionScopeInfo {
 
   void setHasCXXTry(SourceLocation TryLoc) {
     setHasBranchProtectedScope();
-    FirstCXXTryLoc = TryLoc;
+    FirstCXXOrObjCTryLoc = TryLoc;
+    FirstTryType = TryLocIsCXX;
+  }
+
+  void setHasObjCTry(SourceLocation TryLoc) {
+    setHasBranchProtectedScope();
+    FirstCXXOrObjCTryLoc = TryLoc;
+    FirstTryType = TryLocIsObjC;
   }
 
   void setHasSEHTry(SourceLocation TryLoc) {

diff  --git a/clang/lib/Sema/ScopeInfo.cpp b/clang/lib/Sema/ScopeInfo.cpp
index 4857346018ae4..cc7de16de2fdb 100644
--- a/clang/lib/Sema/ScopeInfo.cpp
+++ b/clang/lib/Sema/ScopeInfo.cpp
@@ -37,7 +37,7 @@ void FunctionScopeInfo::Clear() {
   ObjCIsSecondaryInit = false;
   ObjCWarnForNoInitDelegation = false;
   FirstReturnLoc = SourceLocation();
-  FirstCXXTryLoc = SourceLocation();
+  FirstCXXOrObjCTryLoc = SourceLocation();
   FirstSEHTryLoc = SourceLocation();
 
   // Coroutine state

diff  --git a/clang/lib/Sema/SemaStmt.cpp b/clang/lib/Sema/SemaStmt.cpp
index c83ada89d2e07..dc564e318d82d 100644
--- a/clang/lib/Sema/SemaStmt.cpp
+++ b/clang/lib/Sema/SemaStmt.cpp
@@ -4187,7 +4187,14 @@ Sema::ActOnObjCAtTryStmt(SourceLocation AtLoc, Stmt *Try,
   if (!getLangOpts().ObjCExceptions)
     Diag(AtLoc, diag::err_objc_exceptions_disabled) << "@try";
 
-  setFunctionHasBranchProtectedScope();
+  // Objective-C try is incompatible with SEH __try.
+  sema::FunctionScopeInfo *FSI = getCurFunction();
+  if (FSI->FirstSEHTryLoc.isValid()) {
+    Diag(AtLoc, diag::err_mixing_cxx_try_seh_try) << 1;
+    Diag(FSI->FirstSEHTryLoc, diag::note_conflicting_try_here) << "'__try'";
+  }
+
+  FSI->setHasObjCTry(AtLoc);
   unsigned NumCatchStmts = CatchStmts.size();
   return ObjCAtTryStmt::Create(Context, AtLoc, Try, CatchStmts.data(),
                                NumCatchStmts, Finally);
@@ -4423,7 +4430,7 @@ StmtResult Sema::ActOnCXXTryBlock(SourceLocation TryLoc, Stmt *TryBlock,
 
   // C++ try is incompatible with SEH __try.
   if (!getLangOpts().Borland && FSI->FirstSEHTryLoc.isValid()) {
-    Diag(TryLoc, diag::err_mixing_cxx_try_seh_try);
+    Diag(TryLoc, diag::err_mixing_cxx_try_seh_try) << 0;
     Diag(FSI->FirstSEHTryLoc, diag::note_conflicting_try_here) << "'__try'";
   }
 
@@ -4507,9 +4514,12 @@ StmtResult Sema::ActOnSEHTryBlock(bool IsCXXTry, SourceLocation TryLoc,
   // SEH __try is incompatible with C++ try. Borland appears to support this,
   // however.
   if (!getLangOpts().Borland) {
-    if (FSI->FirstCXXTryLoc.isValid()) {
-      Diag(TryLoc, diag::err_mixing_cxx_try_seh_try);
-      Diag(FSI->FirstCXXTryLoc, diag::note_conflicting_try_here) << "'try'";
+    if (FSI->FirstCXXOrObjCTryLoc.isValid()) {
+      Diag(TryLoc, diag::err_mixing_cxx_try_seh_try) << FSI->FirstTryType;
+      Diag(FSI->FirstCXXOrObjCTryLoc, diag::note_conflicting_try_here)
+          << (FSI->FirstTryType == sema::FunctionScopeInfo::TryLocIsCXX
+                  ? "'try'"
+                  : "'@try'");
     }
   }
 

diff  --git a/clang/test/SemaCXX/exceptions-seh.mm b/clang/test/SemaCXX/exceptions-seh.mm
new file mode 100644
index 0000000000000..5efa3c3d91f82
--- /dev/null
+++ b/clang/test/SemaCXX/exceptions-seh.mm
@@ -0,0 +1,25 @@
+// RUN: %clang_cc1 -triple x86_64-windows-msvc -fms-extensions -fsyntax-only -fexceptions -fobjc-exceptions -verify %s
+
+void might_crash();
+
+void use_seh_after_objc() {
+  @try { // expected-note {{conflicting '@try' here}}
+    might_crash();
+  } @finally {
+  }
+  __try { // expected-error {{cannot use Objective-C '@try' in the same function as SEH '__try'}}
+    might_crash();
+  } __except(1) {
+  }
+}
+
+void use_objc_after_seh() {
+  __try { // expected-note {{conflicting '__try' here}}
+    might_crash();
+  } __except(1) {
+  }
+  @try { // expected-error {{cannot use Objective-C '@try' in the same function as SEH '__try'}}
+    might_crash();
+  } @finally {
+  }
+}