diff --git a/autogen.sh b/autogen.sh
index ac48e47..1129f5e 100755
--- a/autogen.sh
+++ b/autogen.sh
@@ -4,6 +4,7 @@
 
 COMMON_CPPFLAGS="-I/usr/local/include"
 COMMON_CFLAGS="-Wall"
+COMMON_CXXFLAGS="${COMMON_CFLAGS}"
 COMMON_LDFLAGS="-L/usr/local/lib"
 COMMON_LDADD=""
 
@@ -23,6 +24,7 @@ echo "ccr_SOURCES = `( find src/ -type f -name \*.c ; find src/ -type f -name \*
 echo "noinst_HEADERS = `find src/ -type f -name \*.h |tr \"\n\" \" \" `" >>$OUT
 echo "ccr_CPPFLAGS = -I\$(srcdir)/$i/ ${COMMON_CPPFLAGS}" >>$OUT
 echo "ccr_CFLAGS = ${COMMON_CFLAGS}" >>$OUT
+echo "ccr_CXXFLAGS = ${COMMON_CXXFLAGS}" >>$OUT
 echo "ccr_LDFLAGS = ${COMMON_LDFLAGS}" >>$OUT
 echo "ccr_LDADD = -lgmp ${COMMON_LDADD} " >>$OUT
 
diff --git a/src/actions.cpp b/src/actions.cpp
index 7c6a56e..38202ed 100644
--- a/src/actions.cpp
+++ b/src/actions.cpp
@@ -96,6 +96,7 @@ int action_gen_key (const std::string& algspec, const std::string&name,
 		return 1;
 	}
 
+	//TODO this can fail, handle it.
 	KR.store_keypair (keyring::get_keyid (pub), name, algname, pub, priv);
 	//pub&priv data will get destroyed along with keyring
 
@@ -1046,6 +1047,7 @@ int action_import (bool armor, bool no_action, bool yes, bool fp,
 		if (keyspec_matches (filter, i->second.name, i->first) ) {
 			KR.remove_pubkey (i->first);
 			KR.remove_keypair (i->first);
+			//TODO this can fail, handle it.
 			KR.store_pubkey (i->first,
 			                 name.length() ?
 			                 name : i->second.name,
@@ -1297,6 +1299,7 @@ int action_import_sec (bool armor, bool no_action, bool yes, bool fp,
 		if (keyspec_matches (filter, i->second.pub.name, i->first) ) {
 			KR.remove_pubkey (i->first);
 			KR.remove_keypair (i->first);
+			//TODO this can fail, handle it.
 			KR.store_keypair (i->first,
 			                  name.length() ?
 			                  name : i->second.pub.name,
diff --git a/src/algos_enc.cpp b/src/algos_enc.cpp
index 8042a80..bbaa85d 100644
--- a/src/algos_enc.cpp
+++ b/src/algos_enc.cpp
@@ -379,7 +379,8 @@ static int fo_decrypt (const bvector&cipher, bvector&plain,
 	ev.colex_rank (ev_rank);
 	ev_rank.resize (ranksize, 0);
 	for (i = 0; i < ranksize; ++i)
-		if (ev_rank[i] != 1 & (H[ (i >> 3) % H.size()] >> (i & 0x7) ) )
+		if (ev_rank[i] != (1 & (H[ (i >> 3) % H.size()]
+		                        >> (i & 0x7) ) ) )
 			return 8;
 
 
diff --git a/src/arcfour.h b/src/arcfour.h
index fd019cb..a7e7fa3 100644
--- a/src/arcfour.h
+++ b/src/arcfour.h
@@ -30,12 +30,13 @@ template<class inttype> class arcfour
 	inttype mask;
 public:
 	bool init (unsigned bits) {
+		size_t Ssize = 1 << bits;
 		if (bits > 8 * sizeof (inttype) ) return false;
 		I = J = 0;
-		S.resize (1 << bits);
+		S.resize (Ssize);
 		mask = ~ (inttype) 0;
 		if ( (inttype) (1 << bits) ) mask %= 1 << bits;
-		for (size_t i = 0; i < (1 << bits); ++i) S[i] = i;
+		for (size_t i = 0; i < Ssize; ++i) S[i] = i;
 		return true;
 	}
 
diff --git a/src/base64.cpp b/src/base64.cpp
index 108da08..b422630 100644
--- a/src/base64.cpp
+++ b/src/base64.cpp
@@ -21,7 +21,7 @@
 void base64_encode (const std::string& in, std::string&out, int cols)
 {
 	//note: it could be b64str[64], but we'd need -fpermissive
-	static const char b64str[65] =
+	static const unsigned char b64str[65] =
 	    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 
 	unsigned int acc = 0;
@@ -50,7 +50,7 @@ void base64_encode (const std::string& in, std::string&out, int cols)
 	}
 }
 
-static void init_dec_str (char s[256])
+static void init_dec_str (unsigned char s[256])
 {
 	for (int i = 0; i < 256; ++i) s[i] = -1;
 
@@ -126,12 +126,12 @@ static void init_dec_str (char s[256])
 	s['/'] = 63;
 }
 
-static inline bool is_white (char c)
+static inline bool is_white (unsigned char c)
 {
 	return (c == '\n') || (c == '\r') || (c == ' ') || (c == '\t');
 }
 
-static inline bool is_b64 (char c)
+static inline bool is_b64 (unsigned char c)
 {
 	return (c >= 'a' && c <= 'z')
 	       || (c >= 'A' && c <= 'Z')
@@ -145,7 +145,7 @@ static void eat_white (const std::string&in, int&idx, int idxmax)
 	for (; (idx < idxmax) && is_white (in[idx]); ++idx);
 }
 
-static bool eat_4 (const std::string&in, int&idx, int idxmax, char*a)
+static bool eat_4 (const std::string&in, int&idx, int idxmax, unsigned char*a)
 {
 	for (int i = 0; i < 4; ++i) {
 		eat_white (in, idx, idxmax);
@@ -159,7 +159,7 @@ static bool eat_4 (const std::string&in, int&idx, int idxmax, char*a)
 
 bool base64_decode (const std::string& in, std::string&out)
 {
-	static char b64d[256];
+	static unsigned char b64d[256];
 	static bool b64d_init = false;
 
 	if (!b64d_init) {
@@ -173,7 +173,7 @@ bool base64_decode (const std::string& in, std::string&out)
 	out.reserve (3 * in.length() / 4);
 
 	//start parsing
-	char c[4];
+	unsigned char c[4];
 	while (eat_4 (in, idx, idxmax, c) ) {
 		for (int i = 0; i < 4; ++i)
 			c[i] = b64d[c[i]]; // '=' gets converted to -1
diff --git a/src/bvector.cpp b/src/bvector.cpp
index 6735587..5991df6 100644
--- a/src/bvector.cpp
+++ b/src/bvector.cpp
@@ -265,7 +265,7 @@ void bvector::colex_rank (bvector&r) const
 
 bool bvector::colex_unrank (bvector&res, uint n, uint k) const
 {
-	mpz_t r, comb, t, t2;
+	mpz_t r, comb, t;
 	mpz_init (r);
 	mpz_init (comb);
 	mpz_init (t);
diff --git a/src/fmtseq.cpp b/src/fmtseq.cpp
index a54d143..7facc3c 100644
--- a/src/fmtseq.cpp
+++ b/src/fmtseq.cpp
@@ -64,10 +64,11 @@ static void store_exist (privkey&priv, const privkey::tree_stk_item&i)
 {
 	uint level = i.level / priv.h;
 	if (level >= priv.l) return; //top node
-	uint sublevel = priv.h - (i.level % priv.h);
-	if (i.pos >= (1 << sublevel) ) return; //too far right
+	uint sublevel = priv.h - (i.level % priv.h),
+	     sublev_width = (uint) 1 << sublevel;
+	if (i.pos >= sublev_width) return; //too far right
 
-	priv.exist[level][i.pos + (1 << sublevel) - 2] = i.item;
+	priv.exist[level][i.pos + sublev_width - 2] = i.item;
 }
 
 static void alloc_desired (privkey&priv, hash_func&hf)
@@ -88,7 +89,7 @@ static void store_desired (privkey&priv, uint did,
 {
 	if ( (i.level / priv.h) != did) return; //too below or above
 	uint depth = priv.h - (i.level % priv.h);
-	if (i.pos >= (1 << depth) ) return; //too far right, omg why?!
+	if (i.pos >= ( (uint) 1 << depth) ) return; //too far right, omg why?!
 	priv.desired[did][i.pos + (1 << depth) - 2] = i.item;
 }
 
@@ -206,7 +207,7 @@ static void update_privkey (privkey&priv, hash_func&hf)
 		uint next_subtree_start =
 		    (1 + (next_sigs_used >> ( (1 + idx) * priv.h) ) )
 		    << ( (1 + idx) * priv.h);
-		if (next_subtree_start >= (1 << (priv.h * priv.l) ) ) {
+		if (next_subtree_start >= ( (uint) 1 << (priv.h * priv.l) ) ) {
 			priv.desired.resize (idx);
 			priv.desired_stack.resize (idx);
 			priv.desired_progress.resize (idx);
diff --git a/src/keyring.cpp b/src/keyring.cpp
index 5e320c5..3e7afe0 100644
--- a/src/keyring.cpp
+++ b/src/keyring.cpp
@@ -299,12 +299,13 @@ static bool ensure_empty_sencode_file (const std::string&fn,
 		l.items.push_back (&b);
 		std::string emptyfile = l.encode();
 
-		int fd, res;
+		int fd;
 		fd = creat (fn.c_str(), S_IRUSR | S_IWUSR);
 		if (fd < 0) return false;
-		res = write (fd, emptyfile.c_str(), emptyfile.length() );
+		ssize_t res = write (fd, emptyfile.c_str(),
+		                     emptyfile.length() );
 		if (close (fd) ) return false;
-		if (res != emptyfile.length() ) return false;
+		if ( (size_t) res != emptyfile.length() ) return false;
 
 	} else {
 		if (!S_ISREG (st.st_mode) )
diff --git a/src/keyring.h b/src/keyring.h
index dc6968e..fc18d9f 100644
--- a/src/keyring.h
+++ b/src/keyring.h
@@ -115,6 +115,7 @@ public:
 		if (pairs.count (keyid) ) return false;
 		if (pubs.count (keyid) ) return false;
 		pubs[keyid] = pubkey_entry (keyid, name, alg, key);
+		return true;
 	}
 
 	void remove_pubkey (const std::string&keyid) {
@@ -138,6 +139,7 @@ public:
 		if (pubs.count (keyid) ) return false;
 		pairs[keyid] = keypair_entry (keyid, name, alg,
 		                              pubkey, privkey);
+		return true;
 	}
 
 	void remove_keypair (const std::string&keyid) {
diff --git a/src/mce_qd.cpp b/src/mce_qd.cpp
index ab2e286..492b279 100644
--- a/src/mce_qd.cpp
+++ b/src/mce_qd.cpp
@@ -64,7 +64,7 @@ int mce_qd::generate (pubkey&pub, privkey&priv, prng&rng,
 		essence[m - 1] = fld.inv (Hsig[0]);
 		//essence[m-1] is now used as precomputed 1/h_0
 
-		for (uint s = 0; (1 << s) < n; ++s) {
+		for (uint s = 0; ( (uint) 1 << s) < n; ++s) {
 			i = 1 << s; //i = 2^s
 
 			Hsig[i] = choose_random (fld.n, rng, used);
@@ -220,7 +220,7 @@ int privkey::prepare()
 	//compute H signature from essence
 	Hsig.resize (n);
 	Hsig[0] = fld.inv (essence[fld.m - 1]);
-	for (s = 0; (1 << s) < n; ++s) {
+	for (s = 0; ( (uint) 1 << s) < n; ++s) {
 		i = 1 << s; //i = 2^s
 
 		Hsig[i] = fld.inv (fld.add (essence[s], essence[fld.m - 1]) );
@@ -246,7 +246,7 @@ int privkey::prepare()
 	g.resize (1, 1); //g(x)=1
 	tmp.clear();
 	tmp.resize (2, 1); //tmp(x)=x+1
-	for (i = 0; i < (1 << T); ++i) {
+	for (i = 0; i < block_size; ++i) {
 		tmp[0] = fld.inv (Hsig[i]); //tmp(x)=x+1/h_i
 		if (used.count (tmp[0]) )
 			return 1;
@@ -286,7 +286,7 @@ int privkey::prepare()
 	tmp.clear();
 	g.resize (1, 1); //g(x)=1
 	tmp.resize (2, 1); //tmp(x)=x+1
-	for (i = 0; i < (1 << T); ++i) {
+	for (i = 0; i < block_size; ++i) {
 		tmp[0] = fld.add (fld.inv (Hsig[i]), omega);
 		g.mult (tmp, fld);
 	}
@@ -351,7 +351,7 @@ int pubkey::encrypt (const bvector & in, bvector & out, const bvector&errors)
 {
 	uint t = 1 << T;
 	bvector p, g, r, cksum;
-	uint i, j, k;
+	uint i, j;
 
 	/*
 	 * shortened checksum pair of G is computed blockwise accordingly to
diff --git a/src/polynomial.cpp b/src/polynomial.cpp
index dfb5063..12df833 100644
--- a/src/polynomial.cpp
+++ b/src/polynomial.cpp
@@ -85,13 +85,12 @@ void polynomial::mod (const polynomial&f, gf2m&fld)
 void polynomial::mult (const polynomial&b, gf2m&fld)
 {
 	polynomial a = *this;
-	uint i, j;
-	int da, db;
+	int da, db, i, j;
 	da = a.degree();
 	db = b.degree();
 
 	clear();
-	if ( (da < 0) || (db < 0) ) //multiply by zero
+	if ( (da < 0) || (db < 0) ) //multiply by zero, not much to do.
 		return;
 
 	resize (da + db + 1, 0);
@@ -261,7 +260,7 @@ void polynomial::make_monic (gf2m&fld)
 	int d = degree();
 	if (d < 0) return;
 	uint m = fld.inv (item (d) );
-	for (uint i = 0; i <= d; ++i) item (i) = fld.mult (item (i), m);
+	for (int i = 0; i <= d; ++i) item (i) = fld.mult (item (i), m);
 }
 
 void polynomial::shift (uint n)
@@ -342,9 +341,9 @@ void polynomial::divmod (polynomial&d, polynomial&res, polynomial&rem, gf2m&fld)
 	int t;
 	while ( (t = rem.degree() ) >= degd) {
 		int rp = t - degd;
-		if (res.size() < rp + 1) res.resize (rp + 1, 0);
+		if ( (int) res.size() < rp + 1) res.resize (rp + 1, 0);
 		res[rp] = fld.mult (headInv, rem[t]);
-		for (uint i = 0; i <= degd; ++i)
+		for (int i = 0; i <= degd; ++i)
 			rem[i + rp] = fld.add (rem[i + rp], fld.mult (res[rp], d[i]) );
 	}
 	rem.strip();
diff --git a/src/qd_utils.cpp b/src/qd_utils.cpp
index 43df826..7fdb4b4 100644
--- a/src/qd_utils.cpp
+++ b/src/qd_utils.cpp
@@ -28,7 +28,7 @@
 
 static void fwht (std::vector<int> x, std::vector<int>&r)
 {
-	int bs, s;
+	uint bs, s;
 	s = x.size();
 	bs = s >> 1;
 	r.swap (x);
diff --git a/src/sencode.cpp b/src/sencode.cpp
index e95f0b3..98c3f73 100644
--- a/src/sencode.cpp
+++ b/src/sencode.cpp
@@ -21,6 +21,11 @@
 #include <sstream>
 #include <list>
 
+/*
+ * TODO
+ * fix: set some maximum integer to avoid overflows and keep the top limit
+ */
+
 static void parse_int (const std::string&str, int&pos, int len,
                        unsigned int&res)
 {
@@ -62,7 +67,7 @@ static void parse_string (const std::string&str, int&pos, int len,
                           std::string&res)
 {
 	//first, read the amount of bytes
-	unsigned int bytes = 0;
+	int bytes = 0;
 
 	/*
 	 * we need to keep this bijective, therefore avoid parsing of any
@@ -84,7 +89,7 @@ static void parse_string (const std::string&str, int&pos, int len,
 		if (pos >= len) goto fail;
 		else if (str[pos] == ':') break; //got it
 		else if ( (str[pos] >= '0') and (str[pos] <= '9') ) //integer
-			bytes = (10 * bytes) + (unsigned int) (str[pos] - '0');
+			bytes = (10 * bytes) + (int) (str[pos] - '0');
 		else goto fail; //weird!
 		++pos;
 	}
@@ -95,7 +100,7 @@ bytes_done:
 	if (pos + bytes >= len) goto fail;
 	res = str.substr (pos, bytes);
 	pos += bytes;
-	--pos; //last char of the bytestring
+	--pos; //set position to last char of the bytestring (not behind it)
 	return;
 fail:
 	pos = -1;
diff --git a/src/sencode.h b/src/sencode.h
index b16c70f..2d46eb2 100644
--- a/src/sencode.h
+++ b/src/sencode.h
@@ -33,6 +33,8 @@ class sencode
 public:
 	virtual std::string encode() = 0;
 	virtual void destroy() {}
+
+	virtual ~sencode() {}
 };
 
 sencode* sencode_decode (const std::string&);