From 090dd647d98dc50a56a42fbba0f3f11b10a3a187 Mon Sep 17 00:00:00 2001
From: Erik Pilkington <erik.pilkington@gmail.com>
Date: Thu, 3 Dec 2020 10:01:53 -0500
Subject: [Sema] Fold VLAs to constant arrays in a few more contexts

552c6c2 removed support for promoting VLAs to constant arrays when the bounds
isn't an ICE, since this can result in miscompiling a conforming program that
assumes that the array is a VLA. Promoting VLAs for fields is still supported,
since clang doesn't support VLAs in fields, so no conforming program could have
a field VLA.

This change is really disruptive, so this commit carves out two more cases
where we promote VLAs which can't miscompile a conforming program:

 - When the VLA appears in an ivar -- this seems like a corollary to the field thing
 - When the VLA has an initializer -- VLAs can't have an initializer

Differential revision: https://reviews.llvm.org/D90871
---
 clang/lib/Parse/ParseDecl.cpp | 37 +++++++++++++++++++++++++++++--------
 1 file changed, 29 insertions(+), 8 deletions(-)

(limited to 'clang/lib/Parse/ParseDecl.cpp')

diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
index 277a67f..c3c56dd 100644
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -2192,7 +2192,22 @@ Decl *Parser::ParseDeclarationAfterDeclaratorAndAttributes(
     }
   };
 
-  // Inform the current actions module that we just parsed this declarator.
+  enum class InitKind { Uninitialized, Equal, CXXDirect, CXXBraced };
+  InitKind TheInitKind;
+  // If a '==' or '+=' is found, suggest a fixit to '='.
+  if (isTokenEqualOrEqualTypo())
+    TheInitKind = InitKind::Equal;
+  else if (Tok.is(tok::l_paren))
+    TheInitKind = InitKind::CXXDirect;
+  else if (getLangOpts().CPlusPlus11 && Tok.is(tok::l_brace) &&
+           (!CurParsedObjCImpl || !D.isFunctionDeclarator()))
+    TheInitKind = InitKind::CXXBraced;
+  else
+    TheInitKind = InitKind::Uninitialized;
+  if (TheInitKind != InitKind::Uninitialized)
+    D.setHasInitializer();
+
+  // Inform Sema that we just parsed this declarator.
   Decl *ThisDecl = nullptr;
   Decl *OuterDecl = nullptr;
   switch (TemplateInfo.Kind) {
@@ -2254,9 +2269,9 @@ Decl *Parser::ParseDeclarationAfterDeclaratorAndAttributes(
     }
   }
 
+  switch (TheInitKind) {
   // Parse declarator '=' initializer.
-  // If a '==' or '+=' is found, suggest a fixit to '='.
-  if (isTokenEqualOrEqualTypo()) {
+  case InitKind::Equal: {
     SourceLocation EqualLoc = ConsumeToken();
 
     if (Tok.is(tok::kw_delete)) {
@@ -2311,7 +2326,9 @@ Decl *Parser::ParseDeclarationAfterDeclaratorAndAttributes(
         Actions.AddInitializerToDecl(ThisDecl, Init.get(),
                                      /*DirectInit=*/false);
     }
-  } else if (Tok.is(tok::l_paren)) {
+    break;
+  }
+  case InitKind::CXXDirect: {
     // Parse C++ direct initializer: '(' expression-list ')'
     BalancedDelimiterTracker T(*this, tok::l_paren);
     T.consumeOpen();
@@ -2365,8 +2382,9 @@ Decl *Parser::ParseDeclarationAfterDeclaratorAndAttributes(
       Actions.AddInitializerToDecl(ThisDecl, Initializer.get(),
                                    /*DirectInit=*/true);
     }
-  } else if (getLangOpts().CPlusPlus11 && Tok.is(tok::l_brace) &&
-             (!CurParsedObjCImpl || !D.isFunctionDeclarator())) {
+    break;
+  }
+  case InitKind::CXXBraced: {
     // Parse C++0x braced-init-list.
     Diag(Tok, diag::warn_cxx98_compat_generalized_initializer_lists);
 
@@ -2381,9 +2399,12 @@ Decl *Parser::ParseDeclarationAfterDeclaratorAndAttributes(
       Actions.ActOnInitializerError(ThisDecl);
     } else
       Actions.AddInitializerToDecl(ThisDecl, Init.get(), /*DirectInit=*/true);
-
-  } else {
+    break;
+  }
+  case InitKind::Uninitialized: {
     Actions.ActOnUninitializedDecl(ThisDecl);
+    break;
+  }
   }
 
   Actions.FinalizeDeclaration(ThisDecl);
-- 
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