diff --git a/Makefile b/Makefile
index c1d0302..63adea4 100644
--- a/Makefile
+++ b/Makefile
@@ -267,7 +267,7 @@ endif
 	emcc -o $@ src/fp.cpp src/bn_c512.cpp $(EMCC_OPT) -DMCL_MAX_BIT_SIZE=512 -DMCL_USE_WEB_CRYPTO_API -s DISABLE_EXCEPTION_CATCHING=1 -DCYBOZU_DONT_USE_EXCEPTION -DCYBOZU_DONT_USE_STRING -fno-exceptions
 
 ../ecdsa-wasm/ecdsa_c.js: src/ecdsa_c.cpp src/fp.cpp include/mcl/ecdsa.hpp include/mcl/ecdsa.h Makefile
-	emcc -o $@ src/fp.cpp src/ecdsa_c.cpp $(EMCC_OPT) -DMCL_MAX_BIT_SIZE=256 -DMCL_USE_WEB_CRYPTO_API -s DISABLE_EXCEPTION_CATCHING=1
+	emcc -o $@ src/fp.cpp src/ecdsa_c.cpp $(EMCC_OPT) -DMCL_MAX_BIT_SIZE=256 -DMCL_USE_WEB_CRYPTO_API -s DISABLE_EXCEPTION_CATCHING=1 -DCYBOZU_DONT_USE_EXCEPTION -DCYBOZU_DONT_USE_STRING -fno-exceptions
 
 mcl-wasm:
 	$(MAKE) ../mcl-wasm/mcl_c.js
diff --git a/include/mcl/ecdsa.hpp b/include/mcl/ecdsa.hpp
index f4ee5c4..d39d3f9 100644
--- a/include/mcl/ecdsa.hpp
+++ b/include/mcl/ecdsa.hpp
@@ -91,16 +91,24 @@ inline void init(bool *pb)
 	Ec::setIoMode(mcl::IoEcAffine);
 	local::Param& p = local::getParam();
 	p.ecParam = ecParam;
-	p.P.set(Fp(ecParam.gx), Fp(ecParam.gy));
+	Fp x, y;
+	x.setStr(pb, ecParam.gx);
+	if (!*pb) return;
+	y.setStr(pb, ecParam.gy);
+	if (!*pb) return;
+	p.P.set(pb, x, y);
+	if (!*pb) return;
 	p.Pbase.init(pb, p.P, ecParam.bitSize, local::winSize);
 }
 
+#ifndef CYBOZU_DONT_USE_EXCEPTION
 inline void init()
 {
 	bool b;
 	init(&b);
 	if (!b) throw cybozu::Exception("ecdsa:init");
 }
+#endif
 
 typedef Zn SecretKey;
 typedef Ec PublicKey;
@@ -111,12 +119,14 @@ struct PrecomputedPublicKey {
 	{
 		pubBase_.init(pb, pub, param.ecParam.bitSize, local::winSize);
 	}
+#ifndef CYBOZU_DONT_USE_EXCEPTION
 	void init(const PublicKey& pub)
 	{
 		bool b;
 		init(&b, pub);
 		if (!b) throw cybozu::Exception("ecdsa:PrecomputedPublicKey:init");
 	}
+#endif
 };
 
 inline void getPublicKey(PublicKey& pub, const SecretKey& sec)
@@ -144,6 +154,7 @@ struct Signature : public mcl::fp::Serializable<Signature> {
 		}
 		s.save(pb, os, ioMode);
 	}
+#ifndef CYBOZU_DONT_USE_EXCEPTION
 	template<class InputStream>
 	void load(InputStream& is, int ioMode = IoSerialize)
 	{
@@ -158,6 +169,8 @@ struct Signature : public mcl::fp::Serializable<Signature> {
 		save(&b, os, ioMode);
 		if (!b) throw cybozu::Exception("ecdsa:Signature:save");
 	}
+#endif
+#ifndef CYBOZU_DONT_USE_STRING
 	friend std::istream& operator>>(std::istream& is, Signature& self)
 	{
 		self.load(is, fp::detectIoMode(Ec::getIoMode(), is));
@@ -168,6 +181,7 @@ struct Signature : public mcl::fp::Serializable<Signature> {
 		self.save(os, fp::detectIoMode(Ec::getIoMode(), os));
 		return os;
 	}
+#endif
 };
 
 inline void sign(Signature& sig, const SecretKey& sec, const void *msg, size_t msgSize)
diff --git a/include/mcl/ecparam.hpp b/include/mcl/ecparam.hpp
index 8c17025..19b76bf 100644
--- a/include/mcl/ecparam.hpp
+++ b/include/mcl/ecparam.hpp
@@ -136,6 +136,7 @@ const struct mcl::EcParam NIST_P521 = {
 
 } // mcl::ecparam
 
+#ifndef CYBOZU_DONT_USE_STRING
 static inline const mcl::EcParam* getEcParam(const std::string& name)
 {
 	static const mcl::EcParam *tbl[] = {
@@ -158,5 +159,6 @@ static inline const mcl::EcParam* getEcParam(const std::string& name)
 	}
 	throw cybozu::Exception("mcl::getEcParam:not support name") << name;
 }
+#endif
 
 } // mcl
diff --git a/include/mcl/window_method.hpp b/include/mcl/window_method.hpp
index b2c3228..cb4fad3 100644
--- a/include/mcl/window_method.hpp
+++ b/include/mcl/window_method.hpp
@@ -109,12 +109,14 @@ public:
 			}
 		}
 	}
+#ifndef CYBOZU_DONT_USE_EXCEPTION
 	void init(const Ec& x, size_t bitSize, size_t winSize)
 	{
 		bool b;
 		init(&b, x, bitSize, winSize);
 		if (!b) throw cybozu::Exception("mcl:WindowMethod:init") << bitSize << winSize;
 	}
+#endif
 	/*
 		@param z [out] x multiplied by y
 		@param y [in] exponent
@@ -129,10 +131,10 @@ public:
 	void mul(Ec& z, int64_t y) const
 	{
 #if MCL_SIZEOF_UNIT == 8
-		Unit u = std::abs(y);
+		Unit u = fp::abs_(y);
 		powArray(z, &u, 1, y < 0);
 #else
-		uint64_t ua = std::abs(y);
+		uint64_t ua = fp::abs_(y);
 		Unit u[2] = { uint32_t(ua), uint32_t(ua >> 32) };
 		size_t un = u[1] ? 2 : 1;
 		powArray(z, u, un, y < 0);
diff --git a/src/ecdsa_c.cpp b/src/ecdsa_c.cpp
index 3b1d53c..f2222a2 100644
--- a/src/ecdsa_c.cpp
+++ b/src/ecdsa_c.cpp
@@ -1,6 +1,7 @@
 #define ECDSA_DLL_EXPORT
 #include <mcl/ecdsa.h>
 #include <mcl/ecdsa.hpp>
+#include <new>
 
 using namespace mcl::ecdsa;
 
@@ -18,6 +19,10 @@ static const PrecomputedPublicKey *cast(const ecdsaPrecomputedPublicKey *p) { re
 
 #ifdef __EMSCRIPTEN__
 // use these functions forcibly
+extern "C" ECDSA_DLL_API void *ecdsaMalloc(size_t n)
+{
+	return malloc(n);
+}
 extern "C" ECDSA_DLL_API void ecdsaFree(void *p)
 {
 	free(p);