Merging r243927, r243932, and r243934:

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r243927 | chandlerc | 2015-08-03 17:44:07 -0700 (Mon, 03 Aug 2015) | 11 lines

[UB] Fix a nasty place where we would pass null pointers to memcpy.

This happens to work, but is not guaranteed to work. Indeed, most memcpy
interfaces in Linux-land annotate these arguments as nonnull, and GCC
and LLVM both can and do optimized based upon that. When they do so,
they might legitimately have miscompiled code calling this routine with
two valid iterators, 'nullptr' and 'nullptr'. There was even code doing
precisely this because StringRef().begin() and StringRef().end() both
produce null pointers.

This was found by UBSan.
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r243932 | chandlerc | 2015-08-03 17:53:01 -0700 (Mon, 03 Aug 2015) | 3 lines

[UB] Fix another place where we would pass a null pointer to memcpy.

This too was found by UBSan. Down to 35 failures for me.
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r243934 | chandlerc | 2015-08-03 18:00:56 -0700 (Mon, 03 Aug 2015) | 4 lines

[UB] Fix yet another use of memcpy with a null pointer argument. I think
this is the last of them in my build of LLVM. Haven't tried Clang yet.

Found via UBSan.
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_37@244224 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/ADT/SmallVector.h b/include/llvm/ADT/SmallVector.h
index 5b208b76a21fa8c465b2b7645c16b649c8e4000e..b9384702c3ba0588d3a402e677a9805d4c471729 100644 (file)
--- a/include/llvm/ADT/SmallVector.h
+++ b/include/llvm/ADT/SmallVector.h
@@ -315,8 +315,10 @@ protected:
                                            T2>::value>::type * = nullptr) {
     // Use memcpy for PODs iterated by pointers (which includes SmallVector
     // iterators): std::uninitialized_copy optimizes to memmove, but we can
-    // use memcpy here.
-    memcpy(Dest, I, (E-I)*sizeof(T));
+    // use memcpy here. Note that I and E are iterators and thus might be
+    // invalid for memcpy if they are equal.
+    if (I != E)
+      memcpy(Dest, I, (E - I) * sizeof(T));
   }
 
   /// Double the size of the allocated memory, guaranteeing space for at

diff --git a/include/llvm/ADT/StringMap.h b/include/llvm/ADT/StringMap.h
index 8721c73b95b13f90b43554376732ebb5590f670b..9d038560bf92d173ac580d5df46766794d22addd 100644 (file)
--- a/include/llvm/ADT/StringMap.h
+++ b/include/llvm/ADT/StringMap.h
@@ -158,7 +158,8 @@ public:
 
     // Copy the string information.
     char *StrBuffer = const_cast<char*>(NewItem->getKeyData());
-    memcpy(StrBuffer, Key.data(), KeyLength);
+    if (KeyLength > 0)
+      memcpy(StrBuffer, Key.data(), KeyLength);
     StrBuffer[KeyLength] = 0;  // Null terminate for convenience of clients.
     return NewItem;
   }

diff --git a/lib/Support/MemoryBuffer.cpp b/lib/Support/MemoryBuffer.cpp
index 98862e96b74923bb930f741d7a9074db8582cdcf..d09ef3a4c0bc595cd0dd95265cb89819f11057fb 100644 (file)
--- a/lib/Support/MemoryBuffer.cpp
+++ b/lib/Support/MemoryBuffer.cpp
@@ -57,7 +57,8 @@ void MemoryBuffer::init(const char *BufStart, const char *BufEnd,
 /// CopyStringRef - Copies contents of a StringRef into a block of memory and
 /// null-terminates it.
 static void CopyStringRef(char *Memory, StringRef Data) {
-  memcpy(Memory, Data.data(), Data.size());
+  if (!Data.empty())
+    memcpy(Memory, Data.data(), Data.size());
   Memory[Data.size()] = 0; // Null terminate string.
 }