[llvm] r284892 - [ADT] Don't rely on string literals not being convertible to non-const char* in CachedHashString.

[Justin Lebar via llvm-commits]

Author: jlebar
Date: Fri Oct 21 17:10:23 2016
New Revision: 284892

URL: http://llvm.org/viewvc/llvm-project?rev=284892&view=rev
Log:
[ADT] Don't rely on string literals not being convertible to non-const char* in CachedHashString.

The build was breaking on some platforms because we assumed that
CachedHashString("foo") would match the CachedHashString(StringRef)
constructor rather than the CachedHashString(char*) constructor.

To fix this, provide a CachedHashString(const char*) constructor, and
add a dummy argument to the old CachedHashString(char*) constructor.

Modified:
    llvm/trunk/include/llvm/ADT/CachedHashString.h

Modified: llvm/trunk/include/llvm/ADT/CachedHashString.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ADT/CachedHashString.h?rev=284892&r1=284891&r2=284892&view=diff
==============================================================================
--- llvm/trunk/include/llvm/ADT/CachedHashString.h (original)
+++ llvm/trunk/include/llvm/ADT/CachedHashString.h Fri Oct 21 17:10:23 2016
@@ -85,7 +85,9 @@ class CachedHashString {
     return P == getEmptyKeyPtr() || P == getTombstoneKeyPtr();
   }
 
-  explicit CachedHashString(char *EmptyOrTombstonePtr)
+  struct ConstructEmptyOrTombstoneTy {};
+
+  CachedHashString(ConstructEmptyOrTombstoneTy, char *EmptyOrTombstonePtr)
       : P(EmptyOrTombstonePtr), Size(0), Hash(0) {
     assert(isEmptyOrTombstone());
   }
@@ -93,6 +95,8 @@ class CachedHashString {
   // TODO: Use small-string optimization to avoid allocating.
 
 public:
+  explicit CachedHashString(const char *S) : CachedHashString(StringRef(S)) {}
+
   // Explicit because copying and hashing a string isn't free.
   explicit CachedHashString(StringRef S)
       : CachedHashString(S, DenseMapInfo<StringRef>::getHashValue(S)) {}
@@ -148,10 +152,12 @@ public:
 
 template <> struct DenseMapInfo<CachedHashString> {
   static CachedHashString getEmptyKey() {
-    return CachedHashString(CachedHashString::getEmptyKeyPtr());
+    return CachedHashString(CachedHashString::ConstructEmptyOrTombstoneTy(),
+                            CachedHashString::getEmptyKeyPtr());
   }
   static CachedHashString getTombstoneKey() {
-    return CachedHashString(CachedHashString::getTombstoneKeyPtr());
+    return CachedHashString(CachedHashString::ConstructEmptyOrTombstoneTy(),
+                            CachedHashString::getTombstoneKeyPtr());
   }
   static unsigned getHashValue(const CachedHashString &S) {
     assert(!isEqual(S, getEmptyKey()) && "Cannot hash the empty key!");