diff --git a/Rcpp/vcfpp-read.cpp b/Rcpp/vcfpp-read.cpp
index dbd29af..bfb4c74 100644
--- a/Rcpp/vcfpp-read.cpp
+++ b/Rcpp/vcfpp-read.cpp
@@ -42,8 +42,8 @@ List tableGL(std::string vcffile, std::string region, std::string samples = "-")
     CharacterVector chr(nsnps), ref(nsnps), alt(nsnps), id(nsnps), filter(nsnps), info(nsnps);
     IntegerVector pos(nsnps);
     NumericVector qual(nsnps);
-    vector<vector<int>> GL(nsnps);
-    vector<int> gl;
+    vector<vector<double>> GL(nsnps); // R only have double
+    vector<float> gl;
     for(int i = 0; i < nsnps; i++)
     {
         vcf.getNextVariant(var);
diff --git a/readme.org b/readme.org
index 32792fc..ca14089 100644
--- a/readme.org
+++ b/readme.org
@@ -21,7 +21,7 @@ Features:
 - [[#installation][Installation]]
 - [[#usage][Usage]]
   - [[#reading-vcf][Reading VCF]]
-  - [[#genotype-values][Genotype values]]
+  - [[#genotypes][Genotypes]]
   - [[#writing-vcf][Writing VCF]]
   - [[#variants-operation][Variants Operation]]
   - [[#header-operation][Header Operation]]
@@ -69,7 +69,12 @@ int main(int argc, char* argv[])
 }
 #+end_src
 
-** Genotype values
+** Genotypes
+There are 3 types used for genotypes, ie vector<bool>, vector<char>
+and vector<int>. One can use vector<bool> and vector<char> for
+memory-effcient goal. The downside is that it only stores 0 and 1. And
+vector<int> can store missing values and multialleles.
+
 *** Code genotypes with missing allele as heterozygous.
 
 If you use =vector<bool>= and =vector<char>= to store the genotypes, then
diff --git a/test/bcf-reader.cpp b/test/bcf-reader.cpp
index 2753f3e..0b06636 100644
--- a/test/bcf-reader.cpp
+++ b/test/bcf-reader.cpp
@@ -63,3 +63,22 @@ TEST_CASE("parse vcf with missing genotypes diploid - vector<int>", "[bcf-reader
     }
     REQUIRE(n == 1);
 }
+
+TEST_CASE("parse vcf with multialleles - vector<int>", "[bcf-reader]")
+{
+    BcfWriter bw("test-multialleles.vcf", "VCF4.3");
+    bw.header.addContig("chr20"); 
+    bw.header.addFORMAT("GT", "2", "String", "Genotype");
+    bw.header.addINFO("AF", "A", "Float", "Estimated allele frequency in the range (0,1)");
+    for(auto & s : {"id01", "id02", "id03"}) bw.header.addSample(s); // add 3 samples
+    bw.writeLine("chr20\t2006060\trs146931526\tG\tA,T\t100\tPASS\tAF=0.02\tGT\t1|2\t1|1\t0|2");
+    bw.close();
+    BcfReader br("test-multialleles.vcf");
+    BcfRecord var(br.header);
+    vector<int> gt;
+    while(br.getNextVariant(var))
+    {
+        var.getGenotypes(gt);
+        for(auto g : gt) cout << g << endl;
+    }
+}
diff --git a/vcfpp.h b/vcfpp.h
index 6b34d30..11ee268 100644
--- a/vcfpp.h
+++ b/vcfpp.h
@@ -163,7 +163,7 @@ class BcfHeader
   public:
     BcfHeader() {}
 
-    virtual ~BcfHeader() {}
+    ~BcfHeader() {}
 
     /** @brief print out the header */
     friend std::ostream & operator<<(std::ostream & out, const BcfHeader & h)
@@ -366,7 +366,7 @@ class BcfRecord
         gtPhase.resize(nsamples, 0);
     }
 
-    virtual ~BcfRecord() {}
+    ~BcfRecord() {}
 
     /** @brief stream out the variant */
     friend std::ostream & operator<<(std::ostream & out, const BcfRecord & v)
@@ -1238,7 +1238,7 @@ class BcfReader
         if(itr) hts_itr_destroy(itr);
     }
 
-    virtual ~BcfReader()
+    ~BcfReader()
     {
         if(fp) hts_close(fp);
         if(itr) hts_itr_destroy(itr);
@@ -1346,6 +1346,7 @@ class BcfWriter
     bcf1_t * b = bcf_init();
     kstring_t s = {0, 0, NULL}; // kstring
     bool isHeaderWritten = false;
+    bool isClosed = false;
 
   public:
     /// header object initialized by initalHeader
@@ -1408,9 +1409,9 @@ class BcfWriter
         initalHeader(h);
     }
 
-    virtual ~BcfWriter()
+    ~BcfWriter()
     {
-        close();
+        if(!isClosed) close();
     }
 
     /**
@@ -1444,8 +1445,9 @@ class BcfWriter
     void close()
     {
         if(!isHeaderWritten) writeHeader();
-        if(fp) hts_close(fp);
         if(b) bcf_destroy(b);
+        if(fp) hts_close(fp);  // be careful of double free
+        isClosed = true;
     }
 
     /// initial a VCF header using the internal template given a specific version. VCF4.1 is the default
@@ -1465,7 +1467,7 @@ class BcfWriter
     /// write a string to a vcf line
     void writeLine(const std::string & vcfline)
     {
-        if(!isHeaderWritten) writeHeader();
+        if(!isHeaderWritten && !writeHeader()) throw std::runtime_error("could not write header out\n");
         std::vector<char> line(vcfline.begin(), vcfline.end());
         line.push_back('\0'); // don't forget string has no \0;
         s.s = &line[0];