don't emit zero bit fields with Emit, fixing undefined behavior,

PR7778


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@111336 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 5 insertions, 3 deletions

diff --git a/include/llvm/Bitcode/BitstreamWriter.h b/include/llvm/Bitcode/BitstreamWriter.h
index 31d513cfb0..bfb3a4e49c 100644
--- a/include/llvm/Bitcode/BitstreamWriter.h
+++ b/include/llvm/Bitcode/BitstreamWriter.h
@@ -88,7 +88,7 @@ public:
   //===--------------------------------------------------------------------===//
 
   void Emit(uint32_t Val, unsigned NumBits) {
-    assert(NumBits <= 32 && "Invalid value size!");
+    assert(NumBits && NumBits <= 32 && "Invalid value size!");
     assert((Val & ~(~0U >> (32-NumBits))) == 0 && "High bits set!");
     CurValue |= Val << CurBit;
     if (CurBit + NumBits < 32) {
@@ -277,10 +277,12 @@ private:
     switch (Op.getEncoding()) {
     default: assert(0 && "Unknown encoding!");
     case BitCodeAbbrevOp::Fixed:
-      Emit((unsigned)V, (unsigned)Op.getEncodingData());
+      if (Op.getEncodingData())
+        Emit((unsigned)V, (unsigned)Op.getEncodingData());
       break;
     case BitCodeAbbrevOp::VBR:
-      EmitVBR64(V, (unsigned)Op.getEncodingData());
+      if (Op.getEncodingData())
+        EmitVBR64(V, (unsigned)Op.getEncodingData());
       break;
     case BitCodeAbbrevOp::Char6:
       Emit(BitCodeAbbrevOp::EncodeChar6((char)V), 6);