diff --git a/classlib/src/main/java/org/teavm/classlib/java/lang/TConsoleOutputStreamStderr.java b/classlib/src/main/java/org/teavm/classlib/java/lang/TConsoleOutputStreamStderr.java
index 0cc2de9ae..8bc0ce3d6 100644
--- a/classlib/src/main/java/org/teavm/classlib/java/lang/TConsoleOutputStreamStderr.java
+++ b/classlib/src/main/java/org/teavm/classlib/java/lang/TConsoleOutputStreamStderr.java
@@ -16,29 +16,31 @@
 package org.teavm.classlib.java.lang;
 
 import java.io.IOException;
+import org.teavm.classlib.PlatformDetector;
 import org.teavm.classlib.java.io.TOutputStream;
-import org.teavm.interop.DelegateTo;
 import org.teavm.interop.Import;
 import org.teavm.interop.Unmanaged;
-import org.teavm.interop.c.Include;
 import org.teavm.jso.JSBody;
 
 class TConsoleOutputStreamStderr extends TOutputStream {
     @Override
-    @DelegateTo("writeLowLevel")
     public void write(int b) throws IOException {
-        writeJs(b);
-    }
-
-    @JSBody(params = "b", script = "$rt_putStderr(b);")
-    private static native void writeJs(int b);
-
-    private void writeLowLevel(int b) {
         writeImpl(b);
     }
 
-    @Include("wchar.h")
+    static void writeImpl(int b) {
+        if (PlatformDetector.isC()) {
+            writeC(b);
+        } else {
+            writeJs(b);
+        }
+    }
+
+    @JSBody(params = "b", script = "$rt_putStderr(b);")
     @Import(name = "putwchar", module = "teavm")
+    private static native void writeJs(int b);
+
     @Unmanaged
-    static native void writeImpl(int b);
+    @Import(name = "teavm_logchar")
+    private static native void writeC(int b);
 }
diff --git a/core/src/main/java/org/teavm/backend/c/generate/ClassGenerator.java b/core/src/main/java/org/teavm/backend/c/generate/ClassGenerator.java
index bd72ddc13..6ab02b08a 100644
--- a/core/src/main/java/org/teavm/backend/c/generate/ClassGenerator.java
+++ b/core/src/main/java/org/teavm/backend/c/generate/ClassGenerator.java
@@ -240,6 +240,9 @@ public class ClassGenerator {
 
         String poolName = "strings_" + context.getNames().forClassInstance(type);
         codeWriter.println("TeaVM_String* " + poolName + "[];");
+        codeWriter.println("#ifdef TEAVM_GET_STRING");
+        codeWriter.println("#undef TEAVM_GET_STRING");
+        codeWriter.println("#endif");
         codeWriter.println("#define TEAVM_GET_STRING(i) " + poolName + "[i]");
     }
 
diff --git a/core/src/main/java/org/teavm/backend/c/generate/CodeGenerationVisitor.java b/core/src/main/java/org/teavm/backend/c/generate/CodeGenerationVisitor.java
index 9af0209af..a5b46392a 100644
--- a/core/src/main/java/org/teavm/backend/c/generate/CodeGenerationVisitor.java
+++ b/core/src/main/java/org/teavm/backend/c/generate/CodeGenerationVisitor.java
@@ -600,7 +600,7 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
         }
 
         if (resultTmp != null) {
-            writer.print(resultTmp + " = ");
+            writer.print(resultTmp + " = (" + typeToCType(method.getResultType()).text + ") ");
         }
         writer.print(names.forMethod(method.getReference()));
         if (method.getAnnotations().get(Variable.class.getName()) == null) {
diff --git a/core/src/main/resources/org/teavm/backend/c/date.c b/core/src/main/resources/org/teavm/backend/c/date.c
index b187a9f5f..3dfa57db0 100644
--- a/core/src/main/resources/org/teavm/backend/c/date.c
+++ b/core/src/main/resources/org/teavm/backend/c/date.c
@@ -48,13 +48,14 @@ int64_t teavm_date_timeToTimestamp(time_t t) {
 }
 
 time_t teavm_date_timestampToTime(int64_t timestamp) {
+    int64_t seconds = (timestamp / 1000);
     struct tm t = {
         .tm_year = 70,
         .tm_mon = 0,
         .tm_mday = 1,
-        .tm_hour = 0,
-        .tm_min = 0,
-        .tm_sec = timestamp / 1000,
+        .tm_hour = (int) (seconds / 3600),
+        .tm_min = (int) ((seconds / 60) % 60),
+        .tm_sec = (int) (seconds % 60),
         .tm_isdst = -1
     };
     return timegm(&t) + timestamp % 1000;
@@ -62,7 +63,10 @@ time_t teavm_date_timestampToTime(int64_t timestamp) {
 
 inline static struct tm* teavm_date_decompose(int64_t timestamp, struct tm *t) {
     *t = teavm_epochStartTm;
-    t->tm_sec += timestamp / 1000;
+    int64_t seconds = (timestamp / 1000);
+    t->tm_sec += (int) (seconds % 60);
+    t->tm_min += (int) ((seconds / 60) % 60);
+    t->tm_hour += (int) (seconds / 3600);
     mktime(t);
     return t;
 }
@@ -179,7 +183,10 @@ int64_t teavm_date_setSeconds(int64_t time, int32_t seconds) {
 char* teavm_date_format(int64_t time) {
     struct tm t;
     t = teavm_epochStartTm;
-    t.tm_sec += time / 1000;
+    int64_t seconds = (time / 1000);
+    t.tm_sec += (int) (seconds % 60);
+    t.tm_min += (int) ((seconds / 60) % 60);
+    t.tm_hour += (int) (seconds / 3600);
     mktime(&t);
     strftime(teavm_date_formatBuffer, 512, teavm_date_defaultFormat, &t);
     return teavm_date_formatBuffer;
diff --git a/core/src/main/resources/org/teavm/backend/c/file.c b/core/src/main/resources/org/teavm/backend/c/file.c
index 1dfc54296..a87496d5f 100644
--- a/core/src/main/resources/org/teavm/backend/c/file.c
+++ b/core/src/main/resources/org/teavm/backend/c/file.c
@@ -587,7 +587,7 @@ int32_t teavm_file_isWindows() {
 }
 
 static TeaVM_StringList* teavm_file_addToList(TeaVM_StringList* strings, char16_t* data) {
-    int32_t size = wcslen(data);
+    int32_t size = (int32_t) wcslen(data);
     WCHAR* copy = malloc(size * sizeof(char16_t));
     memcpy(copy, data, size * sizeof(char16_t));
     return teavm_appendString(strings, copy, size);
diff --git a/core/src/main/resources/org/teavm/backend/c/runtime.c b/core/src/main/resources/org/teavm/backend/c/runtime.c
index 9c0e22a91..5afdbc794 100644
--- a/core/src/main/resources/org/teavm/backend/c/runtime.c
+++ b/core/src/main/resources/org/teavm/backend/c/runtime.c
@@ -62,7 +62,7 @@ static HANDLE teavm_queueTimer;
 #endif
 
 void teavm_beforeInit() {
-    srand(time(NULL));
+    srand((unsigned int) time(NULL));
 
     #ifdef __GNUC__
         setlocale (LC_ALL, "");
@@ -100,7 +100,7 @@ void teavm_beforeInit() {
 
 #ifdef __GNUC__
 void teavm_initHeap(int64_t heapSize) {
-    long workSize = heapSize / 16;
+    long workSize = (long) (heapSize / 16);
     long regionsSize = (long) (heapSize / teavm_gc_regionSize);
 
     long pageSize = sysconf(_SC_PAGE_SIZE);
@@ -166,7 +166,7 @@ static void* teavm_virtualAlloc(int size) {
 }
 
 void teavm_initHeap(int64_t heapSize) {
-    long workSize = heapSize / 16;
+    long workSize = (long) (heapSize / 16);
     long regionsSize = (long) (heapSize / teavm_gc_regionSize);
 
     SYSTEM_INFO systemInfo;
@@ -206,9 +206,8 @@ int64_t teavm_currentTimeNano() {
 #endif
 
 #ifdef _MSC_VER
-#define gmtime_r(a, b) gmtime_s(b, a)
-#define mktime_r(a, b) mktime_s(b, a)
-#define localtime_r(a, b) localtime_s(b, a)
+#define gmtime_r(a, b) gmtime_s(a, b)
+#define localtime_r(a, b) localtime_s(a, b)
 #endif
 
 int32_t teavm_timeZoneOffset() {
@@ -216,7 +215,7 @@ int32_t teavm_timeZoneOffset() {
     time_t t = time(NULL);
     time_t local = mktime(localtime_r(&t, &tm));
     time_t utc = mktime(gmtime_r(&t, &tm));
-    return difftime(utc, local) / 60;
+    return (int32_t) (difftime(utc, local) / 60);
 }
 
 #ifdef __GNUC__
@@ -245,7 +244,7 @@ void teavm_interrupt() {
 #ifdef _MSC_VER
 
 void teavm_waitFor(int64_t timeout) {
-    WaitForSingleObject(teavm_queueTimer, timeout);
+    WaitForSingleObject(teavm_queueTimer, (DWORD) timeout);
     ResetEvent(teavm_queueTimer);
 }
 
@@ -320,7 +319,7 @@ size_t teavm_mbSize(char16_t* javaChars, int32_t javaCharsCount) {
     mbstate_t state = {0};
     for (int32_t i = 0; i < javaCharsCount; ++i) {
         size_t result = c16rtomb(buffer, javaChars[i], &state);
-        if (result == -1) {
+        if (result == (size_t) -1) {
             break;
         }
         sz += result;
@@ -333,7 +332,7 @@ int32_t teavm_c16Size(char* cstring, size_t count) {
     int32_t sz = 0;
     while (count > 0) {
         size_t result = mbrtoc16(NULL, cstring, count, &state);
-        if (result == -1) {
+        if (result == (size_t) -1) {
             break;
         } else if ((int) result >= 0) {
             sz++;
@@ -362,7 +361,7 @@ char* teavm_stringToC(void* obj) {
     mbstate_t state = {0};
     for (int32_t i = 0; i < charArray->size; ++i) {
         size_t result = c16rtomb(dst, javaChars[i], &state);
-        if (result == -1) {
+        if (result == (size_t) -1) {
             break;
         }
         dst += result;
@@ -397,8 +396,8 @@ TeaVM_String* teavm_cToString(char* cstring) {
     char16_t* javaChars = TEAVM_ARRAY_DATA(charArray, char16_t);
     mbstate_t state = {0};
     for (int32_t i = 0; i < size; ++i) {
-        int32_t result = mbrtoc16(javaChars++, cstring, clen, &state);
-        if (result == -1) {
+        size_t result = mbrtoc16(javaChars++, cstring, clen, &state);
+        if (result == (size_t) -1) {
             break;
         } else if ((int) result >= 0) {
             clen -= result;
@@ -429,8 +428,8 @@ char16_t* teavm_mbToChar16(char* cstring, int32_t* length) {
     char16_t* javaChars = malloc(sizeof(char16_t) * (size + 2));
     mbstate_t state = {0};
     for (int32_t i = 0; i < size; ++i) {
-        int32_t result = mbrtoc16(javaChars + i, cstring, clen, &state);
-        if (result == -1) {
+        size_t result = mbrtoc16(javaChars + i, cstring, clen, &state);
+        if (result == (size_t) -1) {
             break;
         } else if ((int) result >= 0) {
             clen -= result;
@@ -542,3 +541,14 @@ TeaVM_StringList* teavm_appendString(TeaVM_StringList* list, char16_t* data, int
     entry->next = list;
     return entry;
 }
+
+#ifndef TEAVM_WINDOWS_LOG
+void teavm_logchar(char16_t c) {
+    putwchar(c);
+}
+#else
+void teavm_logchar(int32_t c) {
+	char16_t buffer[2] = { (char16_t) c, 0 };
+	OutputDebugStringW(buffer);
+}
+#endif
diff --git a/core/src/main/resources/org/teavm/backend/c/runtime.h b/core/src/main/resources/org/teavm/backend/c/runtime.h
index 5a48328da..c3961ac41 100644
--- a/core/src/main/resources/org/teavm/backend/c/runtime.h
+++ b/core/src/main/resources/org/teavm/backend/c/runtime.h
@@ -12,6 +12,8 @@
 #ifdef _MSC_VER
 #define alignas(n) __declspec(align(n))
 #pragma comment (lib,"uuid.lib")
+#pragma warning(disable:4116)
+#pragma warning(disable:4102)
 
 #ifdef WINAPI_FAMILY
     #if WINAPI_FAMILY == 2 || WINAPI_FAMILY == 3 || WINAPI_FAMILY == 5
@@ -353,4 +355,6 @@ extern int32_t teavm_file_isWindows();
 
 #ifdef _MSC_VER
 extern int64_t teavm_unixTimeOffset;
-#endif
\ No newline at end of file
+#endif
+
+extern void teavm_logchar(int32_t);
\ No newline at end of file