Fix warnings and set -Werror

Makefile

@@ -24,9 +24,9 @@ JS_PRE := $(wildcard javascript/*pre.js)
 JS_POST := $(wildcard javascript/*post.js)
 
 CPPFLAGS += -Iinclude -Ilib
-CFLAGS += -Wall -std=c89 -fPIC
-CXXFLAGS += -Wall -std=c++11 -fPIC
-LDFLAGS += -Wall
+CFLAGS += -Wall -Werror -std=c89 -fPIC
+CXXFLAGS += -Wall -Werror -std=c++11 -fPIC
+LDFLAGS += -Wall -Werror
 
 EMCCFLAGS = --closure 1 --memory-init-file 0 -s NO_FILESYSTEM=1 -s INVOKE_RUN=0
 # NO_BROWSER is kept for compatibility with emscripten 1.35.24, but is no

tests/test_olm_decrypt.cpp

@@ -67,7 +67,7 @@ int main() {
 {
 TestCase my_test("Olm decrypt test");
 
-for (int i = 0; i < sizeof(test_cases)/ sizeof(const char *); ++i) {
+for (unsigned int i = 0; i < sizeof(test_cases)/ sizeof(const char *); ++i) {
     decrypt_case(0, test_cases[i]);
 }
 

tests/test_ratchet.cpp

@@ -195,7 +195,7 @@ std::uint8_t random[] = "This is a random 32 byte string";
 for (unsigned i = 0; i < 8; ++i) {
 {
     std::uint8_t msg[alice.encrypt_output_length(sizeof(plaintext))];
-    std::uint8_t encrypt_length = alice.encrypt(
+    alice.encrypt(
         plaintext, 15, random, 32, msg, sizeof(msg)
     );
     std::uint8_t output[bob.decrypt_max_plaintext_length(msg, sizeof(msg))];
@@ -206,7 +206,7 @@ for (unsigned i = 0; i < 8; ++i) {
 random[31]++;
 {
     std::uint8_t msg[bob.encrypt_output_length(sizeof(plaintext))];
-    std::uint8_t encrypt_length = bob.encrypt(
+    bob.encrypt(
         plaintext, 15, random, 32, msg, sizeof(msg)
     );
     std::uint8_t output[alice.decrypt_max_plaintext_length(msg, sizeof(msg))];