From 87cc940604e19bdcdb4a57161d70cb6430b8fb7a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Laurent=20P=C3=A9tr=C3=A9?= <lpetre@ulb.ac.be>
Date: Mon, 7 Jan 2019 00:05:05 +0100
Subject: [PATCH] Fix an improper use of `assign` in the DAC scans

This fixes a bug due to an access to a deleted memory range when
checking the "CACHED" key existence in the LMDB database.

An overload of lmdb::dbi::get is implemented for std::string in order
to check the exsitence of a key in the LMDB database.
---
 include/lmdb_cpp_wrapper.h   | 14 ++++++++++++++
 src/calibration_routines.cpp | 13 +++----------
 2 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/include/lmdb_cpp_wrapper.h b/include/lmdb_cpp_wrapper.h
index ab75f8c..4cdcdcb 100644
--- a/include/lmdb_cpp_wrapper.h
+++ b/include/lmdb_cpp_wrapper.h
@@ -1527,6 +1527,20 @@ class lmdb::dbi {
     return lmdb::dbi_get(txn, handle(), key, data);
   }
 
+  /**
+   * Retrieves a key from this database.
+   *
+   * @param txn a transaction handle
+   * @param key
+   * @throws lmdb::error on failure
+   */
+  bool get(MDB_txn* const txn,
+           const std::string& key) const {
+    const lmdb::val k{key};
+    lmdb::val v{};
+    return lmdb::dbi_get(txn, handle(), k, v);
+  }
+
   /**
    * Retrieves a key from this database.
    *
diff --git a/src/calibration_routines.cpp b/src/calibration_routines.cpp
index 94166a2..2d93307 100644
--- a/src/calibration_routines.cpp
+++ b/src/calibration_routines.cpp
@@ -1149,7 +1149,7 @@ std::vector<uint32_t> dacScanLocal(localArgs *la, uint32_t ohN, uint32_t dacSele
     LOGGER->log_message(LogManager::INFO, stdsprintf("Scanning DAC: %s",regName.c_str()));
     uint32_t adcAddr[24];
     uint32_t adcCacheUpdateAddr[24];
-    bool foundAdcCached=false;
+    bool foundAdcCached = false;
     for(int vfatN=0; vfatN<24; ++vfatN){
         //Skip Masked VFATs
         if ( !( (notmask >> vfatN) & 0x1)) continue;
@@ -1160,11 +1160,7 @@ std::vector<uint32_t> dacScanLocal(localArgs *la, uint32_t ohN, uint32_t dacSele
         //Get ADC address
         if(useExtRefADC){ //Case: Use ADC with external reference
             //for backward compatibility, use ADC1 instead of ADC1_CACHED if it exists
-            lmdb::val key, db_res;
-
-            key.assign(strRegBase+"ADC1_CACHED");
-            foundAdcCached = la->dbi.get(la->rtxn,key,db_res);
-            if(foundAdcCached){
+            if((foundAdcCached = la->dbi.get(la->rtxn, strRegBase + "ADC1_CACHED"))){
                 adcAddr[vfatN] = getAddress(la, strRegBase + "ADC1_CACHED");
                 adcCacheUpdateAddr[vfatN] = getAddress(la, strRegBase + "ADC1_UPDATE");                
             }
@@ -1173,10 +1169,7 @@ std::vector<uint32_t> dacScanLocal(localArgs *la, uint32_t ohN, uint32_t dacSele
         } //End Case: Use ADC with external reference
         else{ //Case: Use ADC with internal reference
             //for backward compatibility, use ADC0 instead of ADC0_CACHED if it exists
-            lmdb::val key, db_res;
-            key.assign(strRegBase+"ADC0_CACHED");
-            foundAdcCached = la->dbi.get(la->rtxn,key,db_res);
-            if(foundAdcCached) {
+            if((foundAdcCached = la->dbi.get(la->rtxn, strRegBase + "ADC0_CACHED"))){
                 adcAddr[vfatN] = getAddress(la, strRegBase + "ADC0_CACHED");
                 adcCacheUpdateAddr[vfatN] = getAddress(la, strRegBase + "ADC0_UPDATE");
             }