Sanitize assert usage and refuse to compile with NDEBUG.

There were quite a few places where assert() was used with side effects,
 making operation with NDEBUG non-functional.  This commit fixes all the
 cases I know about, but also adds an  #error on NDEBUG because the code
 is untested without assertions and may still have vulnerabilities if
 used without assert.

src/main.cpp

@@ -27,6 +27,10 @@
 using namespace std;
 using namespace boost;
 
+#if defined(NDEBUG)
+# error "Bitcoin cannot be compiled without assertions."
+#endif
+
 //
 // Global state
 //
@@ -1266,18 +1270,21 @@ void UpdateTime(CBlockHeader& block, const CBlockIndex* pindexPrev)
 
 void UpdateCoins(const CTransaction& tx, CValidationState &state, CCoinsViewCache &inputs, CTxUndo &txundo, int nHeight, const uint256 &txhash)
 {
+    bool ret;
     // mark inputs spent
     if (!tx.IsCoinBase()) {
         BOOST_FOREACH(const CTxIn &txin, tx.vin) {
             CCoins &coins = inputs.GetCoins(txin.prevout.hash);
             CTxInUndo undo;
-            assert(coins.Spend(txin.prevout, undo));
+            ret = coins.Spend(txin.prevout, undo);
+            assert(ret);
             txundo.vprevout.push_back(undo);
         }
     }
 
     // add outputs
-    assert(inputs.SetCoins(txhash, CCoins(tx, nHeight)));
+    ret = inputs.SetCoins(txhash, CCoins(tx, nHeight));
+    assert(ret);
 }
 
 bool CScriptCheck::operator()() const {
@@ -1651,7 +1658,9 @@ bool ConnectBlock(CBlock& block, CValidationState& state, CBlockIndex* pindex, C
             return state.Abort(_("Failed to write transaction index"));
 
     // add this block to the view's block chain
-    assert(view.SetBestBlock(pindex->GetBlockHash()));
+    bool ret;
+    ret = view.SetBestBlock(pindex->GetBlockHash());
+    assert(ret);
 
     // Watch for transactions paying to me
     for (unsigned int i = 0; i < block.vtx.size(); i++)
@@ -1746,7 +1755,9 @@ bool SetBestChain(CValidationState &state, CBlockIndex* pindexNew)
     // Flush changes to global coin state
     int64_t nStart = GetTimeMicros();
     int nModified = view.GetCacheSize();
-    assert(view.Flush());
+    bool ret;
+    ret = view.Flush();
+    assert(ret);
     int64_t nTime = GetTimeMicros() - nStart;
     if (fBenchmark)
         LogPrintf("- Flush %i transactions: %.2fms (%.4fms/tx)\n", nModified, 0.001 * nTime, 0.001 * nTime / nModified);