From: Eli Friedman <eli.friedman@gmail.com>
Date: Thu, 10 Dec 2009 08:54:47 +0000 (+0000)
Subject: Fix for PR5515: allow "merging" array bounds both forwards and backwards.
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=153c33ed957b135a366178c61bbe22b6b1362a2a;p=clang

Fix for PR5515: allow "merging" array bounds both forwards and backwards.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@91044 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index bf6863bbf4..55a5e7b063 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -1090,10 +1090,11 @@ void Sema::MergeVarDecl(VarDecl *New, LookupResult &Previous) {
   if (getLangOptions().CPlusPlus) {
     if (Context.hasSameType(New->getType(), Old->getType()))
       MergedT = New->getType();
-    // C++ [basic.types]p7:
-    //   [...] The declared type of an array object might be an array of
-    //   unknown size and therefore be incomplete at one point in a
-    //   translation unit and complete later on; [...]
+    // C++ [basic.link]p10:
+    //   [...] the types specified by all declarations referring to a given
+    //   object or function shall be identical, except that declarations for an
+    //   array object can specify array types that differ by the presence or
+    //   absence of a major array bound (8.3.4).
     else if (Old->getType()->isIncompleteArrayType() &&
              New->getType()->isArrayType()) {
       CanQual<ArrayType> OldArray
@@ -1102,6 +1103,14 @@ void Sema::MergeVarDecl(VarDecl *New, LookupResult &Previous) {
         = Context.getCanonicalType(New->getType())->getAs<ArrayType>();
       if (OldArray->getElementType() == NewArray->getElementType())
         MergedT = New->getType();
+    } else if (Old->getType()->isArrayType() &&
+             New->getType()->isIncompleteArrayType()) {
+      CanQual<ArrayType> OldArray
+        = Context.getCanonicalType(Old->getType())->getAs<ArrayType>();
+      CanQual<ArrayType> NewArray
+        = Context.getCanonicalType(New->getType())->getAs<ArrayType>();
+      if (OldArray->getElementType() == NewArray->getElementType())
+        MergedT = Old->getType();
     }
   } else {
     MergedT = Context.mergeTypes(New->getType(), Old->getType());
diff --git a/test/SemaCXX/array-bound-merge.cpp b/test/SemaCXX/array-bound-merge.cpp
new file mode 100644
index 0000000000..579c793368
--- /dev/null
+++ b/test/SemaCXX/array-bound-merge.cpp
@@ -0,0 +1,9 @@
+// RUN: clang-cc -fsyntax-only -verify %s
+// PR5515
+
+extern int a[];
+int a[10];
+extern int b[10];
+int b[];
+extern int c[1];
+int c[] = {1,2}; // expected-error {{excess elements in array initializer}}